How Can I Create Reusable ICommand Implementations in WPF's MVVM Pattern?

Streamlining ICommand Implementation in WPF's MVVM Pattern

In WPF's Model-View-ViewModel (MVVM) architecture, frequent ICommand implementation is common. Creating numerous individual ICommand classes can lead to repetitive code. This article offers a solution for reusable ICommand implementations to enhance efficiency.

A straightforward approach involves a single ICommand class leveraging two delegate methods: one for Execute and one for CanExecute. The constructor accepts these delegates, invoking them within the ICommand methods.

However, a superior alternative, refined from Karl Shifflet's initial concept, is the RelayCommand.

Leveraging the RelayCommand

The RelayCommand class implements the ICommand interface, using Action<T> and Predicate<T> for Execute and CanExecute respectively. This offers a more compact and adaptable method for ICommand implementation.

<code class="language-csharp">public class RelayCommand : ICommand
{
    private readonly Predicate<object> _canExecute;
    private readonly Action<object> _execute;

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

    // ICommand implementation
    // ...
}</code>

Integrating RelayCommand into ViewModel classes simplifies ICommand instantiation.

<code class="language-csharp">public class MyViewModel
{
    private ICommand _doSomething;
    public ICommand DoSomethingCommand
    {
        get
        {
            if (_doSomething == null)
            {
                _doSomething = new RelayCommand(
                    p => this.CanDoSomething(),
                    p => this.DoSomeImportantMethod());
            }
            return _doSomething;
        }
    }
}</code>

Summary

While a custom ICommand implementation with delegates is functional, the RelayCommand provides a more elegant and flexible solution. Adopting RelayCommand significantly streamlines ICommand implementation in MVVM projects.

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