Using `XamlControlsResources.MergedDictionaries` is ignored by the resource resolver

[TopperDEL]

What would you like to be added:

I would love to see ItemsControl.ItemTemplateProperty being implemented.

Why is this needed:

If not implemented I cannot extract a DataTemplate into a ResourceDictionary - I have to place it at the location where it will be used.

For which Platform:

• [X] iOS
• [X] Android
• [ ] WebAssembly
• [ ] WebAssembly renderers for Xamarin.Forms
• [ ] macOS
• [ ] Skia
  • [ ] WPF
  • [ ] GTK (Linux)
  • [ ] Tizen
• [ ] Windows
• [ ] Build tasks
• [ ] Solution Templates

Anything else we need to know?

[jeromelaban]

Thanks for the report!

This property is implemented, so you may be hitting another scenario that we have not seen. Can you provide a repro of the case where it does not work ?

[TopperDEL]

The docs state that it's not implemented.

I have a DataTemplate with a key in a ResourceDictionary that gets loaded on UWP, but is ignored on Android. Will see if I can create a minimal demo.

[TopperDEL]

I've created a sample showing the problem: https://github.com/TopperDEL/ItemTemplateTest

If you run it on UWP, you get some cards-like items. On Android I get a simple list of strings.

GitHub

GitHub - TopperDEL/ItemTemplateTest

Contribute to TopperDEL/ItemTemplateTest development by creating an account on GitHub.

[jeromelaban]

Thanks for the repro. This is looking like more a resource resolution issue than an ItemTemplate issue. Have you tried placing the item template in the page instead of the app-level resource dictionary?

Also, it looks like the docs are incorrect somehow, because this property really is implemented: https://github.com/unoplatform/uno/blob/976c85c29d17754960d8454384f6cad652ea0bdf/src/Uno.UI/UI/Xaml/Controls/ItemsControl/ItemsControl.cs#L209

[jeromelaban]

So the issue really is about resource resolution, and it's related to the way merged dictionaries are declared.

Try using this instead:

<Application
    x:Class="ItemTemplateTest.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:ItemTemplateTest"
    xmlns:controls="using:Microsoft.UI.Xaml.Controls">

    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <controls:XamlControlsResources xmlns="using:Microsoft.UI.Xaml.Controls" />

                <!--<ResourceDictionary Source="uplink.NET.UnoHelpers/Resources/DefaultStyles.xaml" />
                <ResourceDictionary Source="uplink.NET.UnoHelpers/Resources/Animations.xaml" />
                <ResourceDictionary Source="uplink.NET.UnoHelpers/Resources/Converters.xaml" />-->
                <ResourceDictionary Source="Resources/MyStyles.xaml"/>
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>

</Application>

The issue here is caused by the fact that you placed merged dictionaries inside the XamlControlsResources which seems to be ignored by the resources resolver. I'll rename the issue.

[TopperDEL]

Thanks @jeromelaban! I can confirm that this fixes the issue.

The way I added the resources was suggested anywhere - I guess in the Readme of the WCT or something like that.

[jeromelaban]

Interesting. We merged yesterday a contribution that changes the default to be more similar to what I suggested: https://github.com/unoplatform/uno/pull/6884, that'll avoid developers to fall into this trap :)

[davidjohnoliver]

btw ItemTemplateProperty is incorrectly marked NotImplemented because it's currently a field, not a property, which is tripping up the documentation generator. This will be fixed in a future breaking changes roll-up.