Compiled Bindings with Picker.ItemDisplayBinding

[tbrushwyler]

Description

When using Compiled Bindings, there is a compilation error when setting the Picker.ItemDisplayBinding property using the Binding markup extension.

I want to be able to set the data type of a visual element to enable compiled bindings and then set the Picker.ItemDisplayBinding property on one of its ancestors without causing build errors.

Steps to Reproduce

1. Open the reproduction solution (zip, git).
2. Build the solution

Expected Behavior

The solution builds and I can run the app and see three pickers on the page (one should display the result of .ToString() and the other two should display the Name property).

Actual Behavior

There is a build error:

XF_CompiledBindings_Picker/XF_CompiledBindings_Picker/MainPage.xaml(49,49): Error: Position 15:49. Binding: Property 'Name' not found on 'XF_CompiledBindings_Picker.MainPageViewModel' (XF_CompiledBindings_Picker)

Basic Information

• Version with issue: Xamarin.Forms 3.5.0.129452 (also tested against 4.0.0.135213-pre4)
• Last known good version: none
• IDE: 7.7.4
• Platform Target Frameworks:
  • iOS: 12.2.1.15
  • Android: 9.1.8.0
• Nuget Packages: Xamarin.Forms 3.5.0.129452

[StephaneDelcroix]

ItemDisplayBinding is kinda special, as it uses the same syntax as setting a binding, but instead sets a property

[tranb3r]

@StephaneDelcroix
This issue was opened 5 months ago, and so far no progress has been done.
Do you think it could be reprioritized ?

[StephaneDelcroix]

x:DataType="{Null}" in your sample should be x:DataType="{x:Null}" or it will fail with 4.1

[tranb3r]

Yes the sample is wrong, obviously it's x:DataType="{x:Null}".
However, I think we agree this "{x:Null}" datatype is just an ugly workaround.
The real question is: can you fix the issue preventing the sample to build when x:DataType is not set to {x:Null} ?