#1,078 – Defining a Command Binding Using Lambda Expressions

Recall that commands in WPF are objects that you bind UI elements to and that are in turn bound to code for executing the command and for knowing whether a command can be executed.

Below is an example that sets up a command binding using lambda expressions.

    <Window.ContextMenu>
        <ContextMenu>
            <MenuItem Header="Open" Command="ApplicationCommands.Open"/>
        </ContextMenu>
    </Window.ContextMenu>

    <StackPanel>
        <Button Content="Open" Command="ApplicationCommands.Open"
                Margin="10" HorizontalAlignment="Center" />
        <CheckBox Content="Can Open" IsChecked="{Binding CanOpenIsChecked}"
                  Margin="10"/>
    </StackPanel>

We set up the command binding in the window’s constructor.

    public partial class MainWindow : Window, INotifyPropertyChanged
    {
        public MainWindow()
        {
            InitializeComponent();
            this.DataContext = this;

            CommandBindings.Add(new CommandBinding(ApplicationCommands.Open,
                (sender, e) => { MessageBox.Show("Executing the Open command"); },
                (sender, e) => { e.CanExecute = CanOpenIsChecked; }));
        }

        // INotifyPropertyChanged
        public event PropertyChangedEventHandler PropertyChanged = delegate { };

        private void RaisePropertyChanged(string propName)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propName));
        }

        public bool CanOpenIsChecked { get; set; }
    }