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QuestionDependencyProperty fires only in ViewModel.ctor Pin
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GeneralRe: DependencyProperty fires only in ViewModel.ctor Pin
Richard Deeming26-Feb-24 2:19
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That's a strange way of sharing code - uploading a 7zip file to GitHub, rather than uploading your code itself. Laugh | :laugh:

The first thing that jumps out is the PropertyChangedCallback:
C#
private static void ChangeTestInfo(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    var testControl = (TestControl)d;
    testControl.TestInfo = (string)e.NewValue;
}
Thankfully, WPF doesn't call the "property changed" callback if you set the property to the same value it's already set; otherwise, you'd end up with a stack overflow here.

As far as I can see, you want to log the fact that the property has changed, not change the property again:
C#
private static void ChangeTestInfo(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    Debug.WriteLine($"TestInfo changed from '{e.OldValue}' to '{e.NewValue}'.");
}

Beyond that, your code works as expected. Clicking the "set new TestInfo" button shows the new value being set in the debug console. Clicking the "show TestInfo by Button-Click in xaml.cs" button shows the expected new value in the debug console.

Perhaps you were expecting the content of your test control to update? But that's not going to happen: you've set it to the fixed string "TestControl", which isn't bound to anything.

If you want to show the value on the screen, then change your markup to:
XAML
<local:TestControl Content="{Binding Path=TestInfo, ElementName=tct}" x:Name="tct" TestInfo="{Binding TestInfoView}"/>




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GeneralRe: DependencyProperty fires only in ViewModel.ctor Pin
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