RiaTasks: Central Silverlight Business Rules Validation

using System.Windows.Input;
using System;

// From http://johnpapa.net/silverlight/5-simple-steps-to-commanding-in-silverlight/
namespace RIATasks
{
    public class DelegateCommand : ICommand
    {
        Func<object, bool> canExecute;
        Action<object> executeAction;
        bool canExecuteCache;

        public DelegateCommand(Action<object> executeAction, Func<object, bool> canExecute)
        {
            this.executeAction = executeAction;
            this.canExecute = canExecute;
        }

        #region ICommand Members

        public bool CanExecute(object parameter)
        {
            bool temp = canExecute(parameter);

            if (canExecuteCache != temp)
            {
                canExecuteCache = temp;
                if (CanExecuteChanged != null)
                {
                    CanExecuteChanged(this, new EventArgs());
                }
            }

            return canExecuteCache;
        }

        public event EventHandler CanExecuteChanged;

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

        #endregion
    }
}