WPF: How to redefine CanExecute method of ApplicationCommands

Question

I use standard Cut, Copy and Paste commands (which is part of ApplicationCommands class). Is it possible to redefine CanExecute method?

Here is my code:

XAML:

   <Window.CommandBindings>
        <CommandBinding Command="Copy"
                CanExecute="CopyCanExecute" Executed="CopyExecuted"/>       
    </Window.CommandBindings>

    <StackPanel>
        <TextBox Name="txt"></TextBox>
        <Button Command="Copy" CommandTarget="{Binding ElementName=txt}">copy</Button>
    </StackPanel>

Code-behind:

private void CopyCanExecute(object sender, CanExecuteRoutedEventArgs e)
{
    e.CanExecute = false;
}

private void CopyExecuted(object sender, ExecutedRoutedEventArgs e)
{
    MessageBox.Show("Copy Executed");
}  

The button still behave like its command is standard Copy command.

Answer 1

You do this via a CommandBinding. The local CommandBinding can specify a CanExecuteHandler.

For details and a working example, see this blog post.

Answer 2

In the CanExecute handler you might need to add `e.Handled = true; also, so that it doesnt go and execute the standard Copy.CanExecute()