将资源属性绑定到DataContext属性

Question

I was wondering if I could have a child window model in main window resource section and have its properties bound to main model. I have a simple string property on first model and string DependencyProperty on second and tried to bind this way:

<Window.DataContext>
    <local:MainWindowModel x:Name="MainWindowModel"/>
</Window.DataContext>
<Window.Resources>
    <local:SecondWindowModel x:Key="SecondWindowModel" SecondString="{Binding FirstString}"/>
</Window.Resources>

SecondWindowModel is a DependencyObject and SecondString is a DependencyProperty as WPF requires. But SecondString is always null, its setter is never called. Why?

Answer 1

My guess would be that WPF will instanciate the MainWindowModel viewmodel correctly as the Window's DataContext.
But your SecondWindowModel viewmodel being a resource, is actually a .
And in C# a static class is initialized only when you first use it. I'm not sure if WPF initializes its static resources upon declaration.
You can add a static constructor to SecondWindowModel with a break point and check if it is actually initialized before MainWindowViewModel or not at all.