RelayCommand.cs

using System;
using System.Windows.Input;

/// <summary>
/// A command whose sole purpose is to relay its functionality to 
/// other objects by invoking delegates. 
/// The default return value for the CanExecute method is 'true'.
/// </summary>
public class RelayCommand : ICommand
{
    private readonly Action execute;
    private readonly Func<bool> canExecute;

    public event EventHandler CanExecuteChanged;

    public RelayCommand(Action execute) 
        : this(execute, null)
    {
    }

    public RelayCommand(Action execute, 
        Func<bool> canExecute)
    {
        this.execute = execute;
        this.canExecute = canExecute;
    }

    public bool CanExecute(object parameter)
    {
        if (canExecute == null)
        {
            return true;
        }

        return canExecute();
    }

    public void Execute(object parameter)
    {
        execute();
    }

    public void RaiseCanExecuteChanged()
    {
        if (CanExecuteChanged != null)
        {
            CanExecuteChanged(this, EventArgs.Empty);
        }
    }
}