fix #1140 "System.ArgumentNullException: 'Value cannot be null. Parameter name: defaultDestinationValue'" #1398
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…eter name: defaultDestinationValue'"
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Jun 11, 2025
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Pull request type
Please check the type of change your PR introduces:
What is the current behavior?
Issue Number: #1140
Information
I tried to create an example when a crash occurs with the exception
System.ArgumentNullException: 'Value cannot be null. Parameter name: defaultDestinationValue', and also to make a fix for this problem.The example is named
Wpf.Ui.Demo.SetResources.Simple, it implements one problem that I encountered, this is when you create a grouping style for a grid with an expander. The problem is that when you open a page with an expander, everything seems to be fine, but after switching to another page, the application crashes.This problem apparently occurs due to the initialization order. When you use app.resources, this problem does not occur. In the example, I reproduced the situation when the theme resources are not applied at application startup, but are applied when a specific window or page is created.
The example needs to be improved, add another problematic control
CardExpanderapparently it also has this problem, but I was not able to reproduce it in my tests (there is a fix for this control in this PR).