common-delegate-command.md

title	page_title	description	slug	tags	published	position
Delegate Command	DelegateCommand	This article describes the DelegateCommand class, which provides a simple ICommand implementation.	common-mvvm-delegate-command-implementation	delegate,command	true	3

DelegateCommand

The DelegateCommand class provides a simple ICommand implementation. It is located in the Telerik.Windows.Controls namespace and exposes the following methods and events:

• CanExecute: Defines the method that determines whether the command can execute in its current state.
• Execute: Defines the method to be called when the command is invoked.
• InvalidateCanExecute: Raises the CanExecuteChanged event.
• CanExecuteChanged: Raised when changes occur that affect whether the command should execute.

The DelegateCommand constructor has two overloads. The first accepts just a Delegate to execute as a parameter. The second one accepts the Delegate to execute as well as a Predicate that allows/bans the execution.

[C#] Example 1: DelegateCommand implementation in your ViewModel that accepts a delegate and a predicate

{{region cs-common-mvvm-delegate-command-implementation-0}}

public class ViewModel
{
    public bool CanExecuteCommand
    {
        get
        {
            return true;
        }
    }
    public ICommand CustomCommand { get; set; }

    public ViewModel()
    {
        this.CustomCommand = new DelegateCommand(onCustomCommandExecuted, canBeExecuted);
    }

    private bool canBeExecuted(object obj)
    {
        return this.CanExecuteCommand;
    }

    private void onCustomCommandExecuted(object obj)
    {
        MessageBox.Show("Custom Command Executed!");
    }
}

{{endregion}}

[XAML] Example 2: Using the command in xaml

{{region xaml-common-mvvm-delegate-command-implementation-1}}

<Grid>
    <Grid.DataContext>
        <my:ViewModel />
    </Grid.DataContext>

    <Button Command="{Binding CustomCommand}" Content="Execute command" VerticalAlignment="Bottom" />
</Grid>

{{endregion}}

See Also

• [EventToCommandBehavior]({%slug common-event-to-command-behavior%})
• [ViewModelBase]({%slug common-viewmodelbase-class%})
• [Attached Behavior]({%slug common-mvvm-attached-behavior%})