Binding context in ContentPresenter

[smalec]

Reporting this as bug, since it looks fairly similar to #12470

Discussed in #22161

^{Originally posted by smalec May 2, 2024}
Hello, I'm still new in .NET MAUI so I still have some problems with basic concepts and best practices. Currently I'm struggling a bit with ContentPresenter.

So I have a custom component (ContentView) with ControlTemplate that uses ContentPresenter. Let us name this CustomControl.xaml

<ContentView>
    <ContentView.ControlTemplate>
        <ControlTemplate>
            <ContentPresenter />
        </ControlTemplate>
    </ContentView.ControlTemplate>
</ContentView>

Obviously I'm using MVVM so when I want to use CustomControl in a view I do this:

<ContentPage>
    <local:CustomControl>
        <Button Text="Click me" Command="{Binding DoSomethingCommand}" />
    </local:CustomControl>
</ContentPage>

where DoSomethingCommand is defined in my view model.

And this works perfectly fine, awesome! But what if I want to use multiple ContentPresenters in my CustomControl? As far as I know, I should bind content of ContentPresenter like this:

<ContentView>
    <ContentView.ControlTemplate>
        <ControlTemplate>
            <ContentPresenter Content="{TemplateBinding MyContent}" />
        </ControlTemplate>
    </ContentView.ControlTemplate>
</ContentView>

Of course I've defined BindableProperty in my code-behind file. And now I'm using my CustomControl like this:

<ContentPage>
    <local:CustomControl>
        <local:CustomControl.MyContent>
            <Button Text="Click me" Command="{Binding DoSomethingCommand}" />
        </local:CustomControl.MyContent>
    </local:CustomControl>
</ContentPage>

And my button shows up exactly where it should, but... there is absolutely no effect when clicking on it :( I searched for a solution and I found out that I can use it like that:

<Button Text="Click me" Command="{Binding Source={RelativeSource AncestorType={x:Type viewmodels:MyViewModel}}, Path=DoSomethingCommand}" />

And that indeed works, but it looks awful and I don't understand it at all :( Could anyone please help me understand why this simple binding to my command doesn't work? Maybe I can/should modify somehow my CustomControl?

[github-actions]

Hi I'm an AI powered bot that finds similar issues based off the issue title.

Please view the issues below to see if they solve your problem, and if the issue describes your problem please consider closing this one and thumbs upping the other issue to help us prioritize it. Thank you!

Open similar issues:

• ContentPresenter is not clearing its default Content binding when Content is TemplatedBinded in xaml (#22027), similarity score: 0.73
• ControlTemplate not propagating the BindingContext correctly if set through Binding (#22607), similarity score: 0.72
• Binding Context on Content View (#14919), similarity score: 0.71

Closed similar issues:

• ControlTemplate not propagating the BindingContext correctly (#12470), similarity score: 0.74

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[mattleibow]

@StephaneDelcroix thoughts?

[agrisyst-slo]

I have the same problem.
I thought that fix #12536 would solve it, but I have just updated VS to version 17.11.2 and it still does not work.
See the attached test app.
TestMauiAppBindings.zip

If I made a mistake in the controls, please let me know.

Kind regards, Saskia