Why Doesn't My WPF DependencyProperty Binding Update the ViewModel?

Issue with DependencyProperty Binding

This question addresses an issue encountered while implementing a custom File Browser control in WPF. The control features a TextBox bound to a DependencyProperty named "SelectedFile," and a "Browse" button that updates the TextBox value upon clicking.

Despite the correct update of the TextBox, the corresponding view model property "SelectedFile" remained unaffected. The exception was thrown when the binding mode was set to "TwoWay."

Resolution:

The root cause of the issue was incorrectly setting the DataContext of the UserControl to itself in its constructor. This action disrupted data-based bindings.

To rectify this, the binding in the UserControl XAML should be modified as follows:

<TextBox Text="{Binding SelectedFile, RelativeSource={RelativeSource AncestorType=UserControl}}" />

This modification establishes a binding relationship between "SelectedFile" in the UserControl and a property of the same name in the view model. The DataContext inheritance mechanism is employed to propagate the appropriate view model instance.

When the modified XAML is used, the "SelectedFile" property of the view model is bound to and updated accordingly when the user interacts with the File Browser control.

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