Code Snippet.NET2026-03-08

WPF RelayCommand Pattern

A clean implementation of the ICommand interface for WPF MVVM applications. Supports both synchronous and async execution with CanExecute logic.

csharp

public class RelayCommand : ICommand
{
    private readonly Action<object?> _execute;
    private readonly Predicate<object?>? _canExecute;

    public RelayCommand(Action<object?> execute,
        Predicate<object?>? canExecute = null)
    {
        _execute = execute;
        _canExecute = canExecute;
    }

    public event EventHandler? CanExecuteChanged
    {
        add => CommandManager.RequerySuggested += value;
        remove => CommandManager.RequerySuggested -= value;
    }

    public bool CanExecute(object? param) =>
        _canExecute?.Invoke(param) ?? true;

    public void Execute(object? param) => _execute(param);
}

How It Works

RelayCommand is the foundation of the MVVM command pattern in WPF. It wraps any action into an ICommand that can be bound directly to buttons, menu items, and other UI controls.

Constructor takes an execute action and an optional canExecute predicate
CanExecuteChanged hooks into CommandManager.RequerySuggested so WPF automatically re-evaluates button enabled states
Execute simply invokes the stored action with the command parameter

Usage Example

In your ViewModel:

public ICommand SaveCommand => new RelayCommand(
    _ => Save(),
    _ => CanSave);

In your XAML:

<Button Content="Save" Command="{Binding SaveCommand}" />

Tips

For async commands, create an AsyncRelayCommand variant that wraps Func<Task> instead of Action
The CommunityToolkit.Mvvm NuGet package provides production-grade RelayCommand and AsyncRelayCommand implementations
Call CommandManager.InvalidateRequerySuggested() to force WPF to re-check all CanExecute states

WPFMVVMC#.NET