WPF Command with multiple target types

Question

I'm a bit confused about WPF commands with different target types.

So if I define a command

<Window.CommandBindings>
        <CommandBinding Command="Copy"
                        Executed="CopyCmdExecuted"
                        CanExecute="CopyCmdCanExecute"/>

    </Window.CommandBindings>

And now I use it in a context menu:

                    <ContextMenu Name="FolderContextMenu">
                        <MenuItem Command="Copy"/>
                        </ContextMenu>

And I have a method to handle the command:

private void CopyCmdExecuted(object sender, ExecutedRoutedEventArgs e)
{


}

And I use it in a plain old menu:

    <Menu  Name="editMenu">
        <MenuItem Command="Copy"/>
    </Menu>

I have no problem understanding that. But I'm a bit confused what I am supposed to do if the target objects are different types.

Lets say I have Folders and Users, both of which have a context menu with the New command (and the menu bar edit menu which also has the New command).

When New is executed, regardless of whether its a Folder or a User, CopyCmdExecuted is executed. So, am I now supposed to de-multiplex on the target? Something like

   private void CopyCmdExecuted(object sender, ExecutedRoutedEventArgs e)
        {
           if(sender is User)
               // Do copy user stuff
           if(sender is Folder)
               // Do copy folder stuff
        }

If I end up with lots of data types I wish to copy, it seems a bit annoying. Am I not understanding something here?

(Obviously, I could just have Folder and User inherit from a Copiable base class with DoCopy but that still seems wrong.)

Answer 1

You can send a CommandParameter when you invoke the Command to indicate what you mean the command to apply to. Here's are two TextBlock elements:

<Grid>
    <StackPanel>
        <TextBlock Name="textBlock1" Text="File">
            <TextBlock.ContextMenu>
                <ContextMenu>
                    <MenuItem
                        Command="Copy"
                        CommandParameter="{Binding PlacementTarget, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContextMenu}}}"/>
                </ContextMenu>
            </TextBlock.ContextMenu>
        </TextBlock>
        <TextBlock Name="textBlock2" Text="Folder">
            <TextBlock.ContextMenu>
                <ContextMenu>
                    <MenuItem
                        Command="Copy"
                        CommandParameter="{Binding PlacementTarget, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContextMenu}}}"/>
                </ContextMenu>
            </TextBlock.ContextMenu>
        </TextBlock>
    </StackPanel>
</Grid>

and this code-behind:

    private void CopyCmdExecuted(object sender, ExecutedRoutedEventArgs e)
    {
        var text = (e.Parameter as TextBlock).Text;
        Debug.WriteLine("Text = " + text);
    }

uses the parameter to figure out which TextBlock the context menu applies to. You can also just use the strings "File" and "Folder" if that works for you.