Xbox UWP – Unable to Activate Windows Store App – Error 0x8004090a

Building and deploying UWP apps on Xbox is frustrating – every time I come back to it I get caught out by things that should just work. The one that always seems to get me is that you have to be signed in on the Xbox. This used to not be a problem because Visual … Continue reading “Xbox UWP – Unable to Activate Windows Store App – Error 0x8004090a”

Unhelpful ‘Unable to activate Windows Store app’ Error

Building and deploying UWP apps on Xbox is frustrating – every time I come back to it I get caught out by things that should just work. The one that always seems to get me is that you have to be signed in on the Xbox. This used to not be a problem because Visual Studio used to recognise this issue and provide you a nice reminder – I think it was in the Output window but can’t be sure for certain.

I just attempted to debug an app on the Xbox from the latest version of Visual Studio (both preview and stable) and got the following completely unhelpful error message:

Unable to activate Windows Store app 'XXX.YYYYYYYY_ZZZZZZZZApp'. The activation request failed with error 'Operation not supported. Unknown error: 0x8004090a'.

After rebuilding, cleaning the solution, restarting the Xbox and a variety of other things, I remembered to check that a user was signed in on the Xbox. Sure enough it wasn’t and sure enough, signing in, fixed the activation error.

If you come across this error, make sure you’re signed into an account on the Xbox!!!

XAML Back to Basics #3: ListBox/ListView Binding

How to get a ListBoxItem from a data bound ListBox

XAML Basics Series Index Page

The next post in the series originally written by Beatriz Stollnitz. Original post available on Github.

How to get a ListBoxItem from a data bound ListBox

Data binding a list box to an enumeration of items could not be easier in WPF:

    <local:GreekGods x:Key="greekGods"/>
    <DataTemplate x:Key="itemTemplate">
        <TextBlock Text="{Binding Path=Name}" />

<ListBox ItemsSource="{StaticResource greekGods}" ItemTemplate="{StaticResource itemTemplate}" Name="listBox"/>

The ItemsSource property of ListBox takes an IEnumerable, which is the list of items you want to display. In this case, the GreekGods data source is of type ObservableCollection, which implements IEnumerable. The ItemTemplate property specifies the DataTemplate that will be used to control how the data is displayed. In this case, we will have a TextBlock for each item that will display the GreekGod’s name.

Some of you might find surprising, however, that doing listBox.Items[i] in code returns the data we’re binding to, and not the TextBlock or the ListBoxItem. In my opinion, it is actually pretty cool that retrieving the data in a particular position of the list box is so easy, because most of the time this is exactly what you want.

GreekGod greekGod = (GreekGod)(listBox.Items[0]);

But what about when you want to have access to the actual ListBoxItem generated? This is a bit tricky to discover but can be just as easily done with the following code:

ListBoxItem lbi1 = (ListBoxItem)(listBox.ItemContainerGenerator.ContainerFromIndex(0));

There is also a listBox.ItemContainerGenerator.ContainerFromItem(object item) that returns the ListBoxItem given the corresponding data item. This method is frequently used, for example, to retrieve the ListBoxItem for the current item:

ListBoxItem lbi2 = (ListBoxItem)(listBox.ItemContainerGenerator.ContainerFromItem(listBox.Items.CurrentItem));

I will talk about selection and current item in detail in some other post, but for this sample it is sufficient to know that to keep the selection and current item in sync, I set IsSynchronizedWithCurrentItem=”true” in the ListBox.

WPF Source Code


UWP/Uno Notes

There are a couple of changes to the code for UWP/Uno:

  • Whilst the ListBox control still exists, it’s more common to use the ListView as it has a nice set of built in styles
  • The listBox.Items collection doesn’t have a CurrentItem property. Instead we can use listBox.SelectedItem
  • Attempting to set the IsSynchronizedWithCurrentItem property on the ListView (or even ListBox) throws an exception and is generally not required since the SelectedItem property is in sync with what is selected in the ListView.

UWP/Uno Source Code


The structure of the XAML has been left the same from the original post. However, you should really avoid embedding a ListView or ListBox within a StackPanel. This layout will limit the ability of the view to resize without the button being pushed off screen.

Update 15th August 2020

Uno sample has been updated to v3 of Uno and supports iOS, Android, Windows and MacOS.

WinUI with Uno and WinUI for Desktop samples added.

WinUI with Uno and WinUI Desktop Source Code

WinUI – Desktop

XAML Back to Basics #2: Binding Markup

What does “{Binding}” mean?

XAML Basics Series Index Page

The next post in the series originally written by Beatriz Stollnitz. Original post available on Github.

What does “{Binding}” mean?

Most Bindings you see in samples have the Source and Path properties set. The Source property specifies the object you’re binding to and the Path specifies a property in that object whose value you’re interested in. I’ve seen several people get confused when encountering an empty Binding for the first time – “{Binding}”. It seems at first sight that we’re not giving the Binding enough information to do anything useful. This is not true and I will explain why. If you read my previous post you should understand that it is not necessary to set a Source in a Binding, as long as there is a DataContext set somewhere up in the tree. As for the Path, it should be left out when you want to bind to a whole object, and not only to a single property of an object. One scenario is when the source is of type string and you simply want to bind to the string itself (and not to its Length property, for example).

    <system:String x:Key="helloString">Hello</system:String>

<Border DataContext="{StaticResource helloString}">
    <TextBlock TextContent="{Binding}"/>

Another common scenario is when you want to bind some element to an object with several properties.

    <local:GreekGod Name="Zeus" Description="Supreme God of the Olympians" RomanName="Jupiter" x:Key="zeus"/>

<Border DataContext="{StaticResource zeus}">
    <ContentControl Content="{Binding}"/>

In this case, ContentControl does not know how to display the GreekGod data. Therefore you will only see the results of a ToString(), which is typically not what you want. Instead, you can use a DataTemplate, which allows you to specify the appearance of your data.

    <local:GreekGod Name="Zeus" Description="Supreme God of the Olympians" RomanName="Jupiter" x:Key="zeus"/>
    <DataTemplate x:Key="contentTemplate">
            <TextBlock Foreground="RoyalBlue" TextContent="{Binding Path=Name}"/>
            <TextBlock TextContent=":" Margin="0,0,5,0" />
            <TextBlock Foreground="Silver" TextContent="{Binding Path=Description}" />

<Border DataContext={StaticResource zeus}">
    <ContentControl Content="{Binding}" ContentTemplate="{StaticResource contentTemplate}"/>

Notice that none of the Binding statements inside the DataTemplate has a Source. That is because a DataContext is automatically set to the data object being templated.

WPF Source Code


UWP/Uno Source Code

Uno – Wasm

Update 15th August 2020

Uno sample has been updated to v3 of Uno and supports iOS, Android, Windows and MacOS.

WinUI with Uno and WinUI for Desktop samples added.

WinUI with Uno and WinUI Desktop Source Code

WinUI Desktop

17 Years as a Microsoft MVP

Earlier this month I was, was awarded Microsoft MVP for the 17th year and I wanted to take this opportunity to reflect on this. Firstly a note of appreciation to all the Microsoft staff both from the MVP program, the various product teams and of course the Australian sub. Overall an amazing set of people … Continue reading “17 Years as a Microsoft MVP”

Earlier this month I was, was awarded Microsoft MVP for the 17th year and I wanted to take this opportunity to reflect on this. Firstly a note of appreciation to all the Microsoft staff both from the MVP program, the various product teams and of course the Australian sub. Overall an amazing set of people and I always value the opportunities I’ve had along the way to engage with them.

According to the Microsoft website, “Microsoft Most Valuable Professionals, or MVPs, are technology experts who passionately share their knowledge with the community”. For me this points to two key aspects of being an MVP – having good technical knowledge of a particular product and then the ability, and more importantly, the willingness, to share that knowledge with the community.

Over the course of my time as an MVP my engagement with Microsoft and the community has varied considerably. When I was first awarded back in 2004, I had recently created and was running the Perth .NET user group (originally called the Perth .NET Community of Practice). Back then Microsoft did a quarterly roadshow to each state, showcasing and training eager developers. This helped form a network of .NET user groups across Australia, of which only a few still exist today.

When I moved to Sydney I stopped being involved in running a user group but I continued to present and help with various in-person events. User groups were an important mechanism for developers to network and to listen to how other developers were adopting or applying different technologies.

I would say that the heyday for user groups has passed. I used to put it down to everyone being so busy (a typical Sydney attitude) but it dawned on me one day that we’re no more busy than we ever were. User groups were popular because developers would geek out in their personal time to learn the latest and greatest thing. These days I feel that everyone is more conscious of how they spend their very limited personal hours in the day – learning things at a user group is way more like work than it used to be, so why should developers spend their personal hours learning on something they could to at work. These days there are so many learning resources online that it’s easy enough to learn things relatively unassisted, without having to wait for the next user group session.

So, do I think user groups are dead? No, I definitely think there is value to be had in having in-person events. On a similar topic, do I think there is a need for in-person conferences? Again, the answer is that there is value in hosting in-person conferences but it has very little to do with the technical content. What I would challenge, and is something that the COVID-19 situation has accelerated, is that real world events need a digital twin – content, sessions, training and other core conference activities should be able to be done online with the same, or perhaps better, experience online than being at the event. In exchange the real world events have to focus on the human aspect of conferences – more networking, more feedback sessions, more hacking, innovating and pushing the boundaries of what’s possible when you bring 10, 50, 100, 1000 people together. We’re really only at the beginning of this evolution of what the future of user groups will be.

Back when I was first awarded I was working with the .NET Compact Framework and I recall hearing roadmap plans for how the teams were planning to converge with the .NET Framework. To this day, we’re still going through iteration after iteration of convergence; the latest being the .NET 5/6 roadmap. I’ve come to accept that this is a journey that may never be concluded.

Over the course of the last 15 years I’ve had the opportunity to see technologies come and go. I spent a number of years helping to champion firstly Windows Phone and subsequently building for Windows. It was truly awesome to help deliver training to hundreds of developers wanting to build apps for the first time.

These days app development has taken a back seat to the latest trend of drag and drop app builders such as Power Apps, and of course the ever growing world of Azure. With the demise of Windows Phone and the numerous failed attempts at building a market for windows apps, it’s been quite disheartening to see .NET developers looking outside the Microsoft ecosystem for solutions. This has been exacerbated by a massive change in the way Microsoft engages with developers (both locally and from corp) and the almost continual churn of staff and roadmaps; making it near impossible to predict the path forward.

With this said, it truly is an exciting time for app developers with a number of .NET based technologies all showing promise in the cross-platform landscape: DotNetMaui (aka Xamarin.Forms), Uno (UWP+WinUI), Blazor (not really cross platform but with the mobile bindings it’ll interest some) and AvaloniaUI.

The future of these cross-platform technologies relied on providing a platform that will help developers to deliver more applications, across more platforms, as efficiently as possible. Each technology approaches the challenges from a different angle and as such will appeal to different teams and projects. It’s an interesting time to be a developer and watch the space evolve.

As we emerge back out into a post-COVID world (and I know we’re not there yet) what does community look like? How do we leverage or build new technology to allow communities to grow and flourish both online but also in the real world? How can we build global communities that feel the same as the local coffee club? How do we identified leaders in different technologies and harness their skills and knowledge to help each of these global communities.

For user groups and in-person events, COVID-19 was the reset that needed to happen. Let’s work together to build a more sustainable model that both delivers technical knowledge but also helps establish, build and grow global communities.

I’m always up for a chat – connect on LinkedIn, Twitter or just send me an email.

XAML Back to Basics #1: Data Context

How should I decide whether to use DataContext or Source?

XAML Basics Series Index Page

Last year I posted about a series of posts that Beatriz Stollnitz made on WPF/Silverlight that had been moved to GitHub. Unfortunately most of the samples don’t work out of the box with the latest version of Visual Studio but with some minor adjustments they’re easily fixed.

I took a fork of the repository and have started to a) update the wpf projects to work with VS2019 b) remove the Silverlight content and c) add equivalent examples that work cross platform using UWP and the Uno Platform.

Updated Code Samples

Importantly, as I go through each of the posts I’m going to reprint the majority of the original post with edits to bring them up to date with both WPF and UWP/Uno. I want to make sure the Beatriz is recognised as the original author of this content and that I just want to make sure her contributions live on to benefit the next generation of XAML developers.

Original post available on Github

How should I decide whether to use DataContext or Source?

The DataContext is one of the most fundamental concepts in Data Binding.

The Binding object needs to get its data from somewhere, and there are a few ways to specify the source of the data. In this post I talk about setting the Source property directly in the Binding vs inheriting a DataContext from the nearest element when traversing up in the tree. The other two alternatives are setting the ElementName and RelativeSource properties in the Binding object, but I will leave that for a future post.

For example, let’s assume we have the following data sources (GreekGod being a class defined in the code behind):

    <local:GreekGod Name="Zeus" Description="Supreme God of the Olympians" RomanName="Jupiter" x:Key="zeus"/>
    <local:GreekGod Name="Poseidon" Description="God of the sea, earthquakes and horses" RomanName="Neptune" x:Key="poseidon"/>

<StackPanel DataContext="{StaticResource poseidon}">
    <TextBlock TextContent="{Binding Source={StaticResource zeus}, Path=Name}"/>
    <TextBlock TextContent="{Binding Path=Description}"/>
    <TextBlock TextContent="{Binding Path=RomanName}"/>

The first TextBlock inherits the DataContext from the parent StackPanel and has a Source set in the Binding object too. In this case, Source takes priority, causing the TextBlock to bind to the Name property of the resource with key “zeus” – this displays “Zeus”.

The second TextBlock does not have a Source set directly in the Binding object, so it inherits the DataContext from the StackPanel. As you might guess, this binds to the Description property of the resource with key “poseidon”, displaying “God of the sea, earthquakes and horses”.

The third TextBlock should be straightforward – it displays “Neptune”.

Most data bound applications I see from users tend to use DataContext much more heavily than Source. My recommendation is to use DataContext when you need to bind more than one property to a particular source. When binding only one property, it may be better to use the Source attribute . The reason for this is ease of debugging – I would rather see all the information about the Binding in one place than search for the nearest DataContext to understand what is going on. In a small sample like the one above there is no big advantage, but in complex applications this could save you some time.

WPF Source Code


UWP/Uno Notes

In UWP it’s not very common to reference the Windows of the application directly. Instead you can define static resources (in this case the instances of the GreekGod class) at the Application, Page or even Control level. For example, to make the static resource available throughout a given page, we would define them as Page Resources.

    <local:GreekGod Name="Zeus" Description="Supreme God of the Olympians" RomanName="Jupiter" x:Key="zeus"/>
    <local:GreekGod Name="Poseidon" Description="God of the sea, earthquakes and horses" RomanName="Neptune" x:Key="poseidon"/>

UWP/Uno Source Code


Update 15th August 2020

Uno sample has been updated to v3 of Uno and supports iOS, Android, Windows and MacOS.

WinUI with Uno and WinUI for Desktop samples added.

WinUI with Uno and WinUI Desktop Source Code

WinUI Desktop

Don’t Judge XAML Based On Lines of Code

For those following the on-going discussion around the future of XAML and specifically the use of XAML in DotNetMaui/Xamarin.Forms, this post is a follow on from two great posts discussing the options that are, or will be, available for Xamarin.Forms developers as we move forward with DotNetMaui: Mobile Blazor Bindings – Getting Started + Why … Continue reading “Don’t Judge XAML Based On Lines of Code”

For those following the on-going discussion around the future of XAML and specifically the use of XAML in DotNetMaui/Xamarin.Forms, this post is a follow on from two great posts discussing the options that are, or will be, available for Xamarin.Forms developers as we move forward with DotNetMaui:

I’ve already discussed why I feel that DotNetMaui will extend Xamarin.Forms to be an inclusive platform for developers wanting to build cross platform applications. Recent additions to Xamarin.Forms, such as C# markup, coupled with the features outlined on the DotNetMaui roadmap, suggest that the path forward will be full of options for developers.

This bring me to the point of this post, which is to discuss XAML both in the context of DotNetMaui/Xamarin.Forms but also in the context of UWP/WinUI/Uno. To do this I’m going to re-visit the scenario discussed by Dylan and Vincent and look at some alternatives that might make XAML a bit more appealing

Xamarin.Forms Visual States

When I initial read through Dylan’s post and reviewed the XAML I was initially shocked at how hard it was to read and in fact it took me a while to realise why it looked so chaotic and hard to follow. It came down to a couple of things:

  • Changing XAML attribute values based on data triggers at various points in the XAML
  • The lack of Visual States
  • Using MultiTrigger to change attribute values based on multiple data values.

Just so that I’m clear, I’m not saying that the code was poorly written; I’m just observing why I found it hard to read. Let me present an alternative XAML for the page and discuss how it makes the code a little more readable.

<?xml version="1.0" encoding="utf-8"?>
        <local:MainPageViewModel />
        BindableLayout.ItemsSource="{Binding Options}">
                            IsActive="{Binding Selected}" />
                            Value="DarkBlue" />
                            TargetName="OptionsSelectedLabel" />
                            TargetName="OptionsValueLabel" />
                            IsActive="{Binding IsNotEnabled}" />
                            Value="false" />
                            Value="DarkGray" />
                            TargetName="OptionsValueLabel" />
                            Command="{Binding BindingContext.SelectTypeCommand, Source={x:Reference Page}}"
                            CommandParameter="{Binding .}" />
                            IsVisible="false" />
                            Text="{Binding Value}"
                            VerticalOptions="Center" />

On initial inspection you might be looking at this XAML wondering whether it’s improved the readability. However, if you collapse the VisualStateManager.VisualStateGroups node in the editor, the code immediately looks much more readable, as shown in the following image.

We can clearly make out that the interface is made up of a stack of items with each row being made up off a Button and two Label elements. The default state is for the row to have a White background and for the ✓ Label to be hidden (IsVisible set to false).

Now, let’s look at the contents of the VisualStateManager.VisualStateGroups. In this case it defines a single VisualStateGroup in which I’ve included two VisualState elements. If we consider each row it can be in one of three states:

  • Enabled and Not Selected – This is the default state where the item hasn’t been selected (IsEnabled = true, IsSelected = false).
  • Enabled and Selected – This is the state where the item has been selected by the user clicking the Select button (IsEnabled = true, IsSelected = true).
  • Is Not Enabled – When an item in the list is selected, other items may be set to disabled (IsEnabled = false, IsSelected = false).

Even though there are only two VisualStates defined in the XAML, there are in fact three visual states because there is the default state. Each of the VisualState uses a StateTrigger to determine whether the visual state is active or not. Rather than attempting to data bind to two different properties on the underlying data model, I’ve explicitly created single properties that reflect whether the state is active or not. The default state is both the initial state of each row, as well as the state that is returned to if neither of the defined VisualStates are active (ie the StateTrigger IsActive is set to true).

One of the benefits of using visual states is that you can set multiple properties, on one or more different elements, essentially grouping all the changes required for a particular visual states. This eliminates the need to have data triggers littered through the XAML used to define the layout for the page. In this scenario each of the VisualState elements has multiple Setters defining the background colour, the foreground (text) colour and in the case of the IsEnabledAndSelected state, the visibility of the ✓ Label.

As I pointed out earlier, for me, this makes the XAML easier to read. I know other developers prefer to have the data triggers local to where the attributes being changed are in the XAML. This approach has some advantages, particularly where you only have a small number of changes in a large XAML document.

Before we move on from discussing Xamarin.Forms I would point out that the VisualStateManager is a relatively new addition and specifically the ability to use TargetName to target different elements from a single VisualState. I would encourage revisiting your XAML to see whether using the VisualStateManager will simplify your code. Alternatively, you may want to consider breaking your code up into different controls that will help encapsulate things like visual states whilst reducing the complexity of the XAML on each page. We’ll talk more about using UserControls in the context of UWP shortly but the same concept can be used for Xamarin.Forms as well.

UWP / WindowsUI / Uno

The XAML used by the Universal Windows Platform (ie UWP) provides a couple of alternatives when it comes to defining the desired layout. In this section we’re going to consider three options: Optimised, UserControl and ContainerStyle (Code is available on GitHub)

Optimised for Lines of Code

In this approach the goal was simply to reduce the number of lines of code. I’m not going to spend much time on this because I fundamentally think measuring the quality of a technology based on the number of lines of code is just ridiculous. The following image shows the resulting 41 lines of XAML – of course this is also contingent on my Visual Studio settings where the first attribute is on the same line as the element; other developers have different options set, so will see different numbers of lines.

I will comment on a couple of things:

  • Unlike the Xamarin.Forms approach that uses a horizontal StackLayout, this XAML uses a Grid which clearly defines three columns. I prefer this approach as it clearly defines the sizing option for each column. Using a StackLayout with different HorizontalOptions isn’t as clear in my opinion.
  • This code uses x:Bind instead of the usual Binding syntax. This allows for code to be generated during compilation that enforces type checking and results in better performance as it reduces the reliance on reflection.
  • Rather than using converters this code uses static methods defined on the page to convert property values (in some cases multiple properties) into the required attribute value. In practice I would not recommend doing this as it embeds logic in your XAML layout

UserControl with Visual States

In the previous section we optimised the XAML by interleaving logic into our XAML layout. This is a practice that I actively try to avoid when defining the XAML for a page or control. I try to ensure the XAML I create is as declarative as possible, which means avoiding calling methods as part of binding expressions. I’d even go so far as to say that you should avoid using converters unless they are simple type converters (the most obvious one being for bool to Visibility conversion). I advocate for all logic to be encapsulated in either the ViewModel (if UI relate logic) or in the Model (if business logic), thus making it testable and ensuring a clean separation from the way that it’s presented (i.e. the View).

Let’s look at how we can keep our XAML clean of logic by following a similar approach to what we did earlier for Xamarin.Forms. What’s interesting about UWP is that if you attempt to follow the same strategy of defining visual states within the DataTemplate you’ll find that it doesn’t work. Instead you either need to define the visual states within a UserControl, or you have to apply the visual states in the ItemContainerStyle.

We’ll start with defining a UserControl which will include the layout for each item in the list, along with the different visual states. Rather than just show you the code, let’s jump into Blend and use the visual designer to build the desired layout. Rather than boring you with creating the project and adding things like the MainViewModel, I’m just going to focus on creating the UserControl.

From Solution Explorer, right-click on the project or a sub-folder and select Add, New Item.

From the Add New Item dialog, select User Control, give it a name (eg OptionItemControl) and click Add. This should give you a new design surface that we can start adding controls to.

Using the Assets tool window, double-click on the Button and then twice on the TextBlock. Alternatively you can drag these controls onto the design surface.

If you look at the XAML you’ll notice that Blend has added some default attributes to each of the controls that you added. Normally my recommendation would be to tidy up whatever XAML Blend creates, as you go, to ensure your XAML remains clean and does exactly what you want. If you’re not that familiar with XAML, reviewing the XAML that Blend generates is a great way to learn about features that you might not be aware of.

If we look at the design surface we can see that the three controls we added are incorrectly located on the design surface – we’re after a single row with three cells that should hold the “select” Button, a check mark TextBlock and the option value TextBlock.

Let’s go ahead and create the cells in the Grid by defining three columns. We can do this using the design by hovering the mouse near the top of the design surface. The cursor should change to include a small + sign and if you click with the mouse a new column break will be added. You can then use the designer to specify how the column widths are defined. In this case we want the first column to be Auto and the other two columns to be * (just *, so you may have remove any numeric value added by Blend eg 101* should be changed to just *)

Next we want to reposition the two TextBlock into the appropriate column. You can do this by simply dragging them using the mouse. As you drag and hover over each cell in the Grid you’ll see alignment and positioning lines appear in red.

After positioning the TextBlock into the correct column you will want to tidy up the XAML – Blend has an annoying habit of adding Margins and other layout attributes that are typically unnecessary. You can clean up these excess attributes by right-clicking the control and selecting Layout, Reset All.

The next thing to do is to replace the default Text value for the TextBlock from “TextBlock” to something more meaningful. Rather than having to locate the Text property in the properties tool window, you can simply double-click the TextBlock and type directly on the designer. You can do the same thing with the Button control to change the Content to “Select”.

According to the design we’re aiming to achieve we need to change the default (i.e. Enabled but not Selected) Background to White. Use the colour picker in the Properties tool window to do this. This of course will override the theming and thus break support for dark and light themes, but that’s a topic for another day.

Unfortunately setting the Background to White means we can no longer see the three controls, since their default text colour is currently also White. This can be fixed easily by selecting all three controls in the Objects and Timelines tool window.

From the Properties tool window, update the Foreground colour to Black.

You’ll also need to adjust the BorderBrush on the Button. After doing this the layout should be similar to the following.

And the XAML for this is quite tidy.

What’s missing are the visual states for when the option is selected and when it’s disabled. We’ll add two VisualStates to the UserControl via the States window. Normally I advocate for creating a third VisualState that represents the default state – this is so that in code you can use the VisualStateManager GoToState method to return to the default layout. However, we’re going to be using state triggers to transition between states, so a third VisualState is not required – when none of the state triggers are set to active, the UserControl will return to the default state.

By clicking on a VisualState in the States tool window we can put Blend into state editing mode. This is highlighted by both the red dot alongside the VisualState, as well as the red border around the design surface. Any changes you make whilst this highlighting is visible will be recorded against the corresponding VisualState.

I’m not going to go through setting all the properties for each VisualState but essentially we need to update the Background colour on the Grid, the Foreground colour on the TextBlock and Button, and the Visibility on the checkmark TextBlock. For the checkmark TextBlock, you’ll need to switch the default Visibility to Collapsed – we had it visible whilst designing the layout but it’s default state is actually to be hidden (i.e. Collapsed).

As part of defining the VisualStates you may have noticed that the controls in the Objects and Timeline tool window were all given default names like grid, button, textBlock and textBlock1. I would encourage you to give these more meaningful names by double-clicking on them in the Objects and Timeline tool window and typing a new name.

Currently we have completed the design of the UserControl, including the three different states it can be in. However, we haven’t wired it up to any data. If we were to use this UserControl as it is, it would simply show a list of “Option 1”. So that we can wire up some data, let’s add an instance of the OptionViewModel as a design time DataContext for the UserControl (note the use of the d: prefix to indicate design time only).

Select the TextBlock that should show the OptionViewModel Value property. Click on the small square to the right of the Text property in the Properties tool window and select Create Data Binding.

Since we’ve set up an instance of the OptionViewModel as a design time DataContext, Blend is able to offer suggestions for the Path attribute. Select the Value property and click Ok.

At this point you’ll be wondering why the TextBlock that you just setup data binding for as disappeared from the designer. Well, the good news is that the TextBlock is still there, it just has zero width because the Value property on the OptionViewModel is returning null. This is easily fixed by specifying the Value property on the OptionViewModel specified in the design time DataContext.

Ok, we’re almost there. We have our layout, our Visual States and our data. We still need to be able to trigger then changing of states. For this we’re going to use a state trigger. Click the “Edit Adaptive Triggers” button next to the VisualState.

From the Dropdown at the bottom of the screen select <Other Type…>

In our project we have a trigger called DualBooleanDataTrigger which will allow us to trigger a VisualState based on the value of two different bool properties.

Unfortunately this is about as far as the data trigger design experience can take us. Luckily the XAML for the DualBooleanDataTrigger isn’t that complex. As you can see from this image, we need to data bind the DataValue and SecondDataValue attributes to the IsEnabled and IsSelected properties on the OptionViewModel and then we need to specify the value for each of these properties that we want the VisualState to be active for. In this case we want both the IsEnabled and IsSelected properties to be True for this state to be active.

The last thing we need to do is to wire up the Button to a method that will set the OptionViewModel to be selected. For this, we’re going to use x:Bind so that we can bind directly to a method on the OptionViewModel. In order to do this, we need to expose the the OptionViewModel as a property on the UserControl.

In the MainPage (i.e. where we’re defining the ItemsControl) we need to include an instance of the OptionItemControl in the DataTemplate. In order for x:Bind to work we need to make sure we set the ViewModel to be the current DataContext of the DataTemplate (i.e. binding path of . which can be omitted in this scenario).

We then need to specify the Click attribute on the Button.

After completing this we’re done! But let’s take a look at what’s been generated. Well, the good news is that we’ve created the entire user experience without having to write much XAML at all. The bad news is that Blend does a terrible job of generating optimized XAML. Take for example the following snippet where you can see that each Setter is spread over 5 lines.

In contrast, when I tidy these up, each Setter takes only 2 lines and that’s only because I have Visual Studio and Blend set to put attributes on new lines.

As you can see from this walk through, you can use a separate UserControl to easily design the layout for the three states required in this design.

ListView ItemsContainerStyle

The third option I wanted to briefly discuss (because there’s plenty of room for an entire discussion on this topic) is to override the ItemsContainerStyle for a ListView in order to define the VisualStates for the items in the list. Let’s back up for a second and explain a few things.

The scenario that we’re addressing is a common enough scenario where items in a list are selected. In this case the individual item tracks whether it’s selected (and in fact whether it’s enabled). This approach is actually at odds with the way a number of controls work. Take for example the ListView or GridView which are used to represent a list, or grid, of selectable items. Theses controls have built in styles that represent how each ListViewItem will look in various states. These states include (not an exhaustive list) Selected, Pressed, Enabled and Disabled. Further more, these control separate the appearance of each item (specified using the ItemTemplate) from the behaviour when the user interacts with the items (specified in the ControlTemplate used to define the ListViewItem Template nested in the ItemsContainerStyle). Both the ItemTemplate and ItemsContainerStyle are editable using the visual designer, allowing you to customise the appearance of the item and how it changes when the item is selected or enabled/disabled.

For example in Blend we can right-click on a ListView and select Edit Additional Templates, Edit Generated Item Container (ItemContainerStyle) and then either Edit Current, Edit Copy or Create Empty. I would suggest starting by selecting Edit Copy, which will give you a default style that you can customise, rather than starting from scratch.

In the following image you can see how I’ve defined different VisualStates for the ListViewItem to control the appearance for the three states the item can be in. You can also see all the other states that are available by default on the ListViewItem.

At this point you might be asking why, since the ListViewItem already has a Selected and a Disabled state, don’t I just use these. Well, the issue we have is that the Background and Foreground properties have three different colours based on the combination of two different properties (IsEnabled and IsSelected). This means we need to define states that are in the same group that respond to changes in both these properties. This is not how the built in VisualStates are defined. The Selected and Disabled states are in different VisualStateGroups – if we were to use these to control the same properties, we’ll end up with random and chaotic changes in the appearance.

VisualStates in different VisualStateGroups should not control the same property.

This is an important rule and one that’s easily forgotten or broken. If you ever see unusual behaviour relating to visual states, make sure you check this rule.

I’m not going to delve further into how to use the ItemsContainerStyle in this post but feel free to check out the source code. You’ll notice that this is very verbose coming in at around 130 lines, and this is using a much simplified ItemsContainerStyle. Unfortunately due to the complexity of the built in styles, the ItemsContainerStyle is a large style, mainly because the Template for the ListViewItem is so large. Don’t let this put you off considering using this approach because it does mean that you can reuse the style across various lists that may have different content.


Wow, sorry this ended up being quite a long post but hopefully you’ll find it useful and get some insight on the various XAML based options available to you. Don’t forget that all the options presented for UWP are able to be taken cross platform using the Uno Platform.

In summary, yes, XAML is verbose but it does come with options. If you spend time maintaining your XAML you’ll find that it is easy to understand and you can leverage the designer support in Blend and Visual Studio along the way.

I don’t believe that looking at the number of lines of XAML (or C# code) is productive. What is useful is to look at the options that are available and the easy with which you can achieve the desired outcome.

DotNetMaui (Xamarin.Forms) is Not a XAML Platform

Yeh I know I’m going to get a ton of abuse about how this title is just click bait but before you start with the comments, hear me out. Firstly, the title is actually just missing a word DotNetMaui is Not JUST a XAML Platform In this post we’ll go through why DotNetMaui/Xamarin.Forms is/is not … Continue reading “DotNetMaui (Xamarin.Forms) is Not a XAML Platform”

Yeh I know I’m going to get a ton of abuse about how this title is just click bait but before you start with the comments, hear me out. Firstly, the title is actually just missing a word

DotNetMaui is Not JUST a XAML Platform

In this post we’ll go through why DotNetMaui/Xamarin.Forms is/is not a XAML platform and discuss the inclusive approach that the team has taken that allows for the inclusive of approaches such as those proposed by Vincent (C# markup) and James (Comet).

I want to start off by saying that Xamarin.Forms is a great cross-platform technology for rapidly building apps that work across iOS, Android, Windows (UWP), MacOS etc. At Built to Roam we continue to deliver apps for customers using this technology. DotNetMaui will continue this trend and will no doubt be a great platform for developers to build apps that work across various operating systems and devices. This post is in no way supposed to be a criticism, rather an objective look at what DotNetMaui/Xamarin.Forms is and is not. This is 100% from my perspective and I respect that other developers are entitled to their opinions (feel free to leave a comment!)

XAML as Declarative Markup

Historically, there have been various technologies/frameworks that have used XAML as the markup language. Typically, we think of the UI frameworks such as Windows Presentation Foundation (WPF), Silverlight, Windows Phone, Windows (UWP) but XAML has been used as the markup language for other non-UI technologies, for example Windows Workflow Foundation. XAML is fundamentally about declarative markup and in the case of UI frameworks it was for describing layout.

For those developers who have built, or are even still building, using Windows Forms, you’ll remember the pain of trying to coerce the designer to behave. The designer was really just a glorified code generator but the frustration came because if you attempted to modify the generated code, when you reopened the designer it would undo or break your changes. With XAML, this shouldn’t happen because, assuming it’s well-formed, it adheres to the schema…. in theory anyhow.

At this point it’s worth pointing out that in some regards XAML is literally just a way of declaring the creation of a hierarchy of objects. In fact, I’ve often added instances of non-UI classes in XAML just so that they’re available as resources that I can reference from XAML or code throughout my application. If you continue down this line of reasoning, it’s no surprise that you can indeed create your UI in markup (a proposition being peddled heavily by Vincent with his contribution to C# markup for Xamarin.Forms).

XAML Databinding

When developers think about XAML, they often package that together with MVVM and/or data binding. This is not unreasonable since the data binding framework was one of the main selling points that Microsoft would talk about when promoting any XAML technology.

Xamarin.Forms does have great support for data binding. Whilst it doesn’t support the x:Bind syntax introduced in Windows (UWP) which uses code generation to make data binding strongly typed, it does support compiled bindings making XAML quite an efficient technique for defining layout and data binding.

Here’s the question though – if the compiler is just going to convert XAML into compiled code, why don’t we just write it in C# and remove the need to learn the XAML abstraction? (i.e. back to Vincent’s point about C# markup!)

Model-View-Update (MVU)

Over the last couple of years there have been a number of new frameworks and technologies that have provided alternative strategies for updating the UI. Web frameworks such as React use a virtual DOM to deliver rendering efficiencies. More recently we’ve seen Flutter take the learnings from building the rendering engine behind Chrome and applying it as an application framework. This has lead to a lot of excitement about MVU (for the moment I’m going to ignore the argument that Flutter, SwiftUI and Comet/DotNetMaui are not MVU as proposed by the Elm architecture).

There have been several spikes on implementing MVU style frameworks for both Xamarin.Forms and Windows/UWP. All of them that I’ve seen focus on replacing XAML with C# code that declares the layout, with some smarts that only push differences to the UI rendering engine.

As Xamarin.Forms evolves to DotNetMaui we’re going to see some changes to the rendering framework. As the work by James Clancey on Comet is integrated there will be changes to the use of platform renderers. Microsoft is taking a gamble that as they make the necessary changes to Xamarin.Forms/Xamarin.iOS/Xamarin.Android/UWP to align with the .NET roadmap, they’ll take this opportunity to address some of the limitations/frustrations felt by developers with the current rendering engine.

Rendering Engine

There is no proposal to fundamentally change the way that Xamarin.Forms/DotNetMaui uses the native platform controls. The premise is that apps should use the controls that have been provided by the platform. This should encourage developers to build apps that belong on each platform. This thinking is dated, and most customers don’t care about platforms details, they just want their apps to look consistent on every platform.

This lead the team to add the Visual attribute and subsequently the Material Visual. If you’re looking to build a great looking app out of the gate, using the Material Visual is the way to go. However, you do have to ask yourself why did they need to introduce the concept of a Visual when we have styles? and can’t we just change the template of controls to change how they look?

Lookless Controls make a XAML Platform

I’ve conceded early in this post that a XAML platform is really any technology that uses XAML as a markup; thus DotNetMaui/Xamarin.Forms is indeed a XAML platform. However, when we consider what we mean by a XAML platform we typically associate it with a number of capabilities (in no particular order, and I’m sure there are other things that I’ve left off the list):

  • Styles and Resources
  • Data binding
  • Data Templates
  • Visual States
  • Control Templates

Further more I would go so far to say that one of the core principles of a XAML platform is that of Lookless Controls (this term seems to have been lost to history somewhat but was heavily used in the context of WPF and the way controls were templated). This is the ability to completely re-template a control without losing the basic functionality. This is something that has never been adopted by Xamarin.Forms and isn’t likely to emerge in DotNetMaui. In order for a platform to support the concept of Lookless Controls, each control needs to have a ControlTemplate that can be used to define both the static look and feel of the control but also the various Visual States (and transitions) of the control.

Developers considering different cross platform technologies might ask what the difference is between the DotNetMaui/Xamarin.Forms approach and that taken by the Uno Platform. Without listing all the differences, one of the core differences is the support for Lookless Controls and control templating. As ControlTemplates and Visual States are fundamental to the delivery of Lookless Controls on the Windows (UWP/WinUI) platform, they are a core part of the way that the Uno Platform renders apps on each platform.

Not JUST a XAML Platform

The last section seems like I’m being overly negative on the DotNetMaui/Xamarin.Forms platform and I must admit for the longest time I was frustrated that the team hadn’t prioritised making it easier for developers to re-template controls. Whilst I still prefer a platform where I’m in control and can change the template of controls as needed, I recognise that in the majority of cases, this isn’t required in order to deliver great looking apps.

If we look at what’s in scope for DotNetMaui we see that there inclusive approach will provide developers with many options to develop and style their application. This will make DotNetMaui a great starting point for developers wanting to build apps using the Microsoft tool chain, and of course provide a great feeder into building apps that connect and work well with Azure.

Picking Your Platform

At this point you might be asking yourself how do you decide which platform to pick for building your next cross platform application. This is a question that I ask daily and the answer is that it really depends on the situation, the customer, the development team etc. So for a minute, lets limit the scope to the Microsoft ecosystem and consider the following three options:

  • Power Apps – I haven’t talked about these in this post but if you’re looking for a minimal code platform that connects to Microsoft 365 and the Power platform, then this is your best option. It’s not really a true cross platform app platform but worth considering as it’s massively powerful for working with enterprise data and workflows
  • DotNetMaui/Xamarin.Forms – If you’re looking to rapidly deliver great looking apps where the designs are derived from the Material design language without wanting to curate animations, effects and styles, then DotNetMaui/Xamarin.Forms is the way to go. Pick the approach (eg MVVM or MVU) and language (eg C# or XAML) that suits your team.
  • Uno Platform/WinUI – If you’re looking for granular control over every aspect of your application then you can’t go past the Uno Platform. This platform is evolving at an amazing pace providing support for Web Assembly, Skia backend and much more. Each control has a ControlTemplate that you can override and customise precisely the way you want it.

Windows (UWP) Point Animations

A week or so ago I noticed a really slick piece of animation done as part of a Flutter app. Unfortunately I can no longer find the tweet as the account has been removed. However, it perked my interest enough to go playing with animations in XAML to see what I can do. Note that … Continue reading “Windows (UWP) Point Animations”

A week or so ago I noticed a really slick piece of animation done as part of a Flutter app. Unfortunately I can no longer find the tweet as the account has been removed. However, it perked my interest enough to go playing with animations in XAML to see what I can do. Note that I’m not trying to reproduce the original sample, just demonstrate that can be done with a bit of XAML and a bit of code.

Since I can’t show you the original animation, I’ll skip to the end and show you what I came up with. What you’re seeing in the following animated GIF is a drag animation that follows the mouse/touch pointer across the screen – imagine you’re using this to reveal a side menu or a different part of the UI of the app.

Ok, so how did I achieve this. Well, whilst I’d love to say that it was as easy as opening Blend, drawing a curve and then recording a storyboard, that is NOT what happened. In fact there’s almost no designer support for creating either the curve or the storyboard, mainly because it involves defining and then animation a path. However, with this said, I did do all the coding in Blend for Visual Studio and it did update the designer as I made changes.

If we take a look at a single frame, we can see what the shape is that we’re going to try to create.

Starting in the top left corner (0,0) we need a path that consists of

  • Horizontal line to (20,0)
  • Vertical line to (20,100)
  • A curve to (80,150)
  • A curve to (20,200)
  • Vertical line to (20,1000)
  • Horizontal line to (0,1000)
  • Vertical line to (0,0) to close the shape

In XAML this looks like

<Path x:Name="path"

                    <PathFigure StartPoint="0,0">
                                <LineSegment Point="20,0"
                                                x:Name="StartLine" />
                                <LineSegment Point="20,100"
                                <BezierSegment Point1="20,125"
                                                Point3="80,150" />
                                <BezierSegment Point1="80,165"
                                                Point3="20,200" />
                                <LineSegment Point="20,1000" x:Name="BottomLine"
                                <LineSegment Point="0,1000"
                                                x:Name="EndLine" />

The next part is to animate this shape, which we can do by creating a storyboard and then moving each of the points on the shape. From the Objects and Timeline tool window, click the green + button to create a new Storyboard, which we’ve called our customStoryboard. Unfortunately this is where the designer support for animations runs out.

Dropping into XAML we can define the animations that make up the storyboard

    <Storyboard x:Name="customStoryboard">
        <PointAnimationUsingKeyFrames Storyboard.TargetProperty="Point"
            <LinearPointKeyFrame KeyTime="0:0:0.5"
        <PointAnimationUsingKeyFrames Storyboard.TargetProperty="Point"
            <LinearPointKeyFrame KeyTime="0:0:0.5"
        <PointAnimationUsingKeyFrames Storyboard.TargetProperty="Point1"
            <LinearPointKeyFrame KeyTime="0:0:0.5"
        <PointAnimationUsingKeyFrames Storyboard.TargetProperty="Point2"
            <LinearPointKeyFrame KeyTime="0:0:0.5"
        <PointAnimationUsingKeyFrames Storyboard.TargetProperty="Point3"
            <LinearPointKeyFrame KeyTime="0:0:0.5"
        <PointAnimationUsingKeyFrames Storyboard.TargetProperty="Point1"
            <LinearPointKeyFrame KeyTime="0:0:0.5"
        <PointAnimationUsingKeyFrames Storyboard.TargetProperty="Point2"
            <LinearPointKeyFrame KeyTime="0:0:0.5"
        <PointAnimationUsingKeyFrames Storyboard.TargetProperty="Point3"
            <LinearPointKeyFrame KeyTime="0:0:0.5"
        <PointAnimationUsingKeyFrames Storyboard.TargetProperty="Point"
            <LinearPointKeyFrame KeyTime="0:0:0.5"

After defining the storyboard, now you can return to the Objects and Timeline window and select the storyboard from the dropdown. Once selected you can position the cursor in the timezone.

At close to the 0.5 second mark (close to completion for most animations) the screen looks like this – definitely on the right track

Up to this point we’ve defined a set of line segments that make up a connected entity and a basic animation that simply adjusts the position of the points. What’s left to do is for the animation to track the mouse cursor or touch point.

We’re going to intercept and handle the Pointer_Moved event that is raised whenever a pointer moves across the page. In the event handler we need to calculate and apply the new position co-ordinates so that the animation can be amended.

The following code illustrate updating values (points) in the animation.

   public MainPage()

            SizeChanged += MainPage_SizeChanged;

        private void MainPage_SizeChanged(object sender, SizeChangedEventArgs e)
            Part1.Point3 = new Point(500, e.NewSize.Height / 2);
            Part2.Point2 = new Point(50, e.NewSize.Height - 100);
            Part2.Point3 = new Point(0, e.NewSize.Height);
            EndLine.Point = new Point(0, e.NewSize.Height);

        private void Start_Animation(object sender, RoutedEventArgs e)
        const int StartWidth = 50;
        const int MaxDiffX = 400;
        const double HeightToWidthRatio = 1.5;
        private void path_PointerMoved(object sender, PointerRoutedEventArgs e)
            // The location of the center is where the mouse/touch point is
            var newCenter = e.GetCurrentPoint(this).Position;
            var part1_point3 = newCenter;

            // Next determine the width of the shape
            var startX = Math.Max(StartWidth, newCenter.X - MaxDiffX);
            var width = newCenter.X - startX;

            // Calculate the height of the shape using the ratio
            var height = width * HeightToWidthRatio;

            // As we approach the other size, calculate how much space there is
            // and if close, reduce the width of the shape accordingly
            var remainingWidth = ActualWidth - newCenter.X;
            if (remainingWidth < width)
                width = remainingWidth;
                startX = Math.Max(StartWidth, newCenter.X - width);

            // The first line goes from 0,0 out along the X axis
            var start_point = new Point(startX, 0);
            // The last line goes from 0,<actual height> out along the X axis
            var end_point = new Point(startX, this.ActualHeight);

            // Calculate top and bottom of the shape
            var top = newCenter.Y - height / 2;
            var top_point = new Point(start_point.X, top);
            var bottom = newCenter.Y + height / 2;
            var part2_point3 = new Point(start_point.X, bottom);

            // Spread the remaining points in the shape
            var part1_point1 = new Point(start_point.X, top+ height * 0.25);
            var part1_point2 = new Point(newCenter.X, top+ height * 0.35);
            var part2_point1 = new Point(newCenter.X, top + height * 0.65);
            var part2_point2 = new Point(start_point.X, top+ height * 0.75);

            StartLinePoint.Value = start_point;
            TopLinePoint.Value = top_point;
            Part1Point1.Value = part1_point1;
            Part1Point2.Value = part1_point2;
            Part1Point3.Value = part1_point3;
            Part2Point1.Value = part2_point1;
            Part2Point2.Value = part2_point2;
            Part2Point3.Value = part2_point3;
            BottomLinePoint.Value = end_point;

            if (customStoryboard.GetCurrentState() != Windows.UI.Xaml.Media.Animation.ClockState.Stopped)


And that’s it – a basic animation written in XAML, with a bit of code behind to check temp. It’s worth pointing out that the use of point based animations will result in smooth animations, rather than simply setting the points directly on the shape.

Building Messages in Blend for Visual Studio

The other day Martin Zikmond tweeted about a messaging sample app he’d built using the Uno Platform, allowing the same app to run on iOS, Android, Windows, MacOS and Web. Whilst the concept was simple enough, the point was that there was almost no platform specific code and yet the app works and looks virtually … Continue reading “Building Messages in Blend for Visual Studio”

The other day Martin Zikmond tweeted about a messaging sample app he’d built using the Uno Platform, allowing the same app to run on iOS, Android, Windows, MacOS and Web. Whilst the concept was simple enough, the point was that there was almost no platform specific code and yet the app works and looks virtually the same on every platform.

Following my previous post where I did a walk through of some of the Blend for Visual Studio features I use, I thought I’d take the challenge to see how much of Martin’s app I could build using the designer in Blend. The good news is that you can get a long way; The bad news is that there are some features, such as ThemeResources, that seem to cause some issues with the designer – we’ll see this towards the end of the post.

New Project

Ok, so this is pretty self explanatory but Blend has a similar New Project experience to what you see in Visual Studio. Start by searching for the type of project you want to build. So that the designer works, we’re going to select a Blank App (Universal Windows). Once we’ve completed the design work we can copy the files across into our Uno project

Note: At the moment there’s no support for Shared Projects, which the default Uno solution is setup to use. If you follow my post on using multi-targeting with Uno you can use the designer if you load the Windows solution filter.

Give your project a name and location you want it saved.

At this point I typically make sure the application runs and that I’ve upgraded various NuGet packages. Next I’m going to copy in a bunch of the code files from Martin’s project that is available on GitHub. This includes the ViewModels, the SampleData and a couple of Assets.

In the code behind for the MainPage (MainPage.xaml.cs) I’ve added a ViewModel property that returns an instance of the MainViewModel. This will be used to provide both runtime and design time data.

Now let’s get to the designer. From the Assets tool window, search for “split” and drag the SplitView onto the design surface. The SplitView has a Pane, the collapsable panel that shows/hides when you tab the burger menu, and a main Content area. In Martin’s app the list of conversations is in the Pane, whilst the Messages for the selected conversation appear in the Content area.

I wanted to reuse the same color resources that Martin has, so I copied the contents of the App.xaml across to my project – It would be awesome if Microsoft could add back support for managing project resources, which was previously a feature of Blend but got lost in the update to the designer a couple of years ago.

Back to the designer and focus on the SplitView. From the Properties tool window locate the PaneBackground property. Select the Color Resources tab (yeh, Editor and Color Resources are a tab, not that it’s very obvious) and select the NavPaneBackgroundColor (this comes from the resources we added to App.xaml). Whilst we’re here, set the BackgroundSource property to HostBackdrop and TintOpacity to 50%. Check out the docs on Acrylic material for more information on using Windows specific brushes. This is one point where Martin has provided a different background for Windows versus the other platforms – check out the source code to see how he’s done this using platform namespaces.

When you launch the app on Windows you can see the effect of setting the Acrylic background on the pane of the splitview (left side of this image).

Next we’re going to set the Padding on the Grid located inside the Pane, which will inset the list of conversations away from the edge. Rather than just setting the Padding, which can be done using the Properties tool window, I’m going to convert this into a reusable resource. Click the square to the right of the property to display the context menu, then select Convert to New Resource.

Give the resource a name and specify where you want the resource to be saved.

In this case I’m going to go ahead and create a new Resource dictionary by clicking the New… button. Since we’ll use this resource dictionary for styles, templates and other resources, I’ve named it accordingly. When you click the Add button, not only does this resource dictionary get added to your project, it is also wired up as a merge dictionary in App.xaml.

Next we’re going to add a ListView to the Pane to display the list of conversations. Again from the Assets window, drag the ListView across onto the Pane in the designer.

Unfortunately there’s no designer support for working with x:Bind. However, you will get intellisense in the XAML editor to let you know what properties are available for binding to.

Despite setting the ItemsSource property, the ListView still remains empty on the designer – as I mentioned, no designer support for x:Bind. However, with the recently introduced design time data everywhere support that’s been added, you can take advantage of regular data binding at design time.

Firstly, we’ll add an instance of the MainViewModel as design time resource. Note that this is the same as adding normal resources, just with the “d:” prefix. However, be aware that setting attributes at design time will override any runtime values whilst in the designer. This normally isn’t an issue but when specifying resources, it will only pick up the design time resources, rather than attempting to combine the resource dictionaries.

        <MainViewModel x:Key="DesignViewModel" />

Note that the XAML editor is able to assist with applying namespaces etc. After adding the MainViewModel resource I get a prompt helping me to setup and use the namespace.

Next, set the ItemsSource property on the ListView, again using the design time prefix (i.e. d:ItemsSource=”{Binding Conversations}” ). Now we should start to see items appear in the ListView.

Let’s go ahead and create a data template for determining how each item will appear. Right-click on the ListView and select Edit Additional Templates, Edit Generated Items (ItemTemplate), followed by Create Empty. Give the DataTemplate a name and specify where you want to save it.

Rather than going through each element in the item template, I’m going to add the DataTemplate from Martin’s code. However, even after adding this data template, there’s no items appearing in the ListView. Again, this is because there’s no designer support for x:Bind. Luckily we can do the same trick, this time for each property we want to data bind. in this example we’re using the design time data binding for the Text property on the TextBlock

Ok, so now we’re starting to look good.

However, notice how the time is appearing at different positions for each item in the list. This is because the list item isn’t spanning the full width of the ListView. I’ve never understood why this is the default behaviour but it dates back as long as I can remember. Luckily there’s an easy fix, which is to set the HorizontalContentAlignment on the ListView to Stretch. However, this needs to be done on the ItemContainerStyle for the ListView. Right-click on the ListView, Edit Additional Templates and then this time select Edit Generated Item Container (ItemContainerStyle), followed by Create Empty.

Give the template a name and location for saving.

From the Properties tool window, search for “horizon” and change the HorizontalContentAlignment to Stretch (far right icon).

Now, the list of conversations is looking much better.

In the main Content area, lets start by creating three rows to host the header, messages and input TextBox. Using the mouse, you can draw the grid rows, and then use the designer to define the height for the rows. The first and third row should both be set to Auto, with the second row set to *.

Let’s add the input TextBox at the bottom of the screen. Click on the chevrons on the left edge of the design to expand out the Assets flyout. Search for textbox and double-click on the TextBox to add it to the designer.

Next, right-click on the newly created TextBox and select Layout, Reset All.

Depending on where the TextBox was added, you’ll probably have to set the Grid.Row to 2 in order for it to appear in the third row. Whilst in the Properties tool window, let’s set the CornerRadius to 12 and the Margin to 20 – again, I would typically extract these to resources so they can be reused across the app (similar to CSS classes if you’re more familiar with styling for the web).

At this point I’m going to grab the rest of the XAML for the Content area from Martin’s source code, rather than walking you through adding each of the controls. There was one exception to this – in Martin’s code he has used an ItemTemplateSelector to switch between two different item templates based on whether the message is from the current user or not. I’m going to take a different approach, so I’ve replaced the ItemTemplateSelector with just a single ItemTemplate. The resulting messages list looks like the following, where it’s no longer possible to distinguish who sent which message.

To fix this issue we’re going to use converters that take a bool value and determine what value to return. The first converter returns a HorizontalAlignment, either Left or Right, depending on the input value. I’ve set it to return Stretch if the input value isn’t a bool, effectively making it the default value.

Next we’re going to make use of this converter in the item template. Here we’ve selected the Border element and are about to click the Create Data Binding menu item.

In the Create Data Binding window, we select the IsFrom property, and then at the bottom of the window, select the BoolHorizontalAlignmentConverter.

If you run the app at this point you’ll see that the messages are aligned left and right according to who sent the message but there’s no difference in style. We can do the same process but this time for setting the Style of different elements in the template; this time using a BoolStyleConverter.

The difference with the BoolStyleConverter is that it needs a TrueStyle and FalseStyle to be defined. For example for the Border we can create two styles and then an instance of the BoolStyleConverter.

And the same for the TextBlock style

And then we apply these to the item template.

And voila, we have a similar layout to what Martin had

Ok, so just in conclusion there’s a couple of points:

  • Firstly, in the style for the Border and TextBlock it’s referencing a ThemeResource to set color. This is important so that you get support for light/dark mode. However, it also seems to break the designer support, resulting in no messages appearing on the screen. I think the resolution might be that the Styles themselves have to be defined as ThemeResources.
  • Secondly, you might be asking why I chose to use converters instead of an ItemTemplateSelector. The answer is that there isn’t any right or wrong answer, I just wanted to demonstrate a different way to appear the problem. In some cases the ItemTemplateSelector is preferred, particularly if there are massive differences between the templates. In this case, I would probably go with converters because you have a single ItemTemplate, so any changes you make will affect both From and To messages, without you having to remember to update both templates.

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