Calling SetBinding after setting a constant value crashes

[fsdsabel]

Description

If I set a binding on a control in code behind after a constant value has been set, the application crashes with an ArgumentException: An item with the same key has already been added. Key: Microsoft.Maui.Controls.SetterSpecificity (Parameter 'key')

This is new behavior in .NET 8 as I cannot reproduce this with .NET 7. We use this heavily in our quite large application with many user controls and for us it is almost a blocker for migration to .NET 8. There might be a workaround but it's difficult to spot all the instances this is happening. We are really looking forward to 8 as we are dealing with a lot of bugs in 7 that are really slowing us down.

Steps to Reproduce

1. Create a File -> New MAUI App
2. Replace the content of OnCounterClicked in MainPage.xaml.cs with this:

// if CounterBtn already has a binding set on BackgroundColor, this sequence crashes immediately, otherwise it crashes the second time it's called
CounterBtn.BackgroundColor = Colors.Coral;            
CounterBtn.SetBinding(BackgroundColorProperty, new Binding(nameof(BackgroundColor), source: this));

4. Run the app (verified on Windows)
5. Click the "Click me" button twice. The second time the app will crash.

Link to public reproduction project repository

No response

Version with bug

8.0.0-rc.1.9171

Is this a regression from previous behavior?

Yes, this used to work in .NET MAUI

Last version that worked well

7.0.92

Affected platforms

Android, Windows, I was not able test on other platforms

Affected platform versions

All

Did you find any workaround?

No. Even clearing the binding or setting the property to null doesn't help.

Relevant log output

No response

[StephaneDelcroix]

it's probably already fixed, I'll write a test to be 100% sure

[fsdsabel]

Yes it's fixed in the current nightly. Thanks!

[MauiUIui]

Yes it's fixed in the current nightly. Thanks!

How did you get the nightly build? Could you please point it out?

[fsdsabel]

Yes it's fixed in the current nightly. Thanks!

How did you get the nightly build? Could you please point it out?

I used the steps provided here: https://github.com/dotnet/installer/blob/main/README.md

In my case I used the alternative NuGet package source and updated to the latest nightly build in package manager. Make sure to check "Include prerelease". One culprit though: The RC1 build are listet at the top of the list. You have to scroll a bit to find the nightly builds. I didn't see that at first. There are a lot of builds.