#1,199 – Complete WPF Command Example

Below is a cheat sheet for creating a custom command in WPF.

Use a static property to expose a command object from the ViewModel or code-behind. RoutedUICommand allows for associating control text with the command itself.

private static RoutedUICommand _pressMeCommand = 
    new RoutedUICommand("Press Me", "PressMe", typeof(MainWindow));
public static RoutedUICommand PressMeCommand
{
    get { return _pressMeCommand; }
}

Add command handlers (in code-behind or ViewModel).

private void PressMe_CanExecute(object sender, CanExecuteRoutedEventArgs e)
{
    e.CanExecute = CowboyCanTalk;
}
 
private void PressMe_Executed(object sender, ExecutedRoutedEventArgs e)
{
    MessageBox.Show("Howdy howdy I'm a cowboy");
}

Bind the command to its handlers, done here in XAML for a window.

<Window.CommandBindings>
    <CommandBinding Command="local:MainWindow.PressMeCommand" 
                    CanExecute="PressMe_CanExecute" 
                    Executed="PressMe_Executed"/>
</Window.CommandBindings>

Wire a button up to the command. Note use of command’s Text property for the button’s Content (text).

<Button Command="local:MainWindow.PressMeCommand" 
        Content="{Binding RelativeSource={RelativeSource Self}, Path=Command.Text}" />

We can also wire up the command to other GUI elements, e.g. a menu item in a context menu. The menu item’s text is set up automatically.

<Window.ContextMenu>
    <ContextMenu>
        <MenuItem Command="{x:Static local:MainWindow.PressMeCommand}" />
    </ContextMenu>
</Window.ContextMenu>
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About Sean
Software developer in the Twin Cities area, passionate about software development and sailing.

3 Responses to #1,199 – Complete WPF Command Example

  1. Pingback: Dew Drop - February 6, 2017 (#2415) - Morning Dew

  2. IGood says:

    When naming commands (re: both the identifier & the string arg), is there a standard or best practice? i.e.
    // 1. doesn’t use a suffix on the identifier, no string literals
    Commit = new RoutedCommand(nameof(Commit), …);
    // 2. follows DependencyProperty style (ex: TextProperty & “Text”) but uses a string literal
    CommitCommand = new RoutedCommand(“Commit”, …);
    // 3. incorrect option? uses both identifier suffix & `nameof` so we end up with an undesirable name
    CommitCommand = new RoutedCommand(nameof(CommitCommand), …);

    I’d say #1 would be the no-brainer if not for WPF’s convention of adding suffixes on identifiers (like TextProperty or ValueChangedEvent).
    I guess the difference here is that commands don’t represent 1 piece of a 2-part setup the way that dependency properties & routed events do.

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