I've created buttons that are bound to FileDialogCommands for sending commands to an ExplorerControl, as shown here:
Everything works when the ExplorerControl is visible. However, if the ExplorerControl's Visibility is set to Collapsed (which I need based on a condition), the Command bindings on the buttons throw the below error:
System.NullReferenceException: Object reference not set to an instance of an object.
at Telerik.Windows.Controls.FileDialogs.ExplorerControl.CanExecuteHelper(Object sender)
The UserControl that hosts the ExplorerControl is being imported through MEF. I don't know if that's a factor.
Either way, it looks like a null check might be needed for the InternalViewModel property.