vocab_manager/Command/RelayCommand.cs

using System;
using System.Diagnostics;
using System.Windows.Input;

namespace VocabManager.Command
{
    /// <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
    {
        #region Fields

        readonly Action<object> _execute;
        readonly Predicate<object> _canExecute;        

        #endregion // Fields

        #region Constructors

        /// <summary>
        /// Creates a new command that can always execute.
        /// </summary>
        /// <param name="execute">The execution logic.</param>
        public RelayCommand(Action<object> execute)
            : this(execute, null)
        {
        }

        /// <summary>
        /// Creates a new command.
        /// </summary>
        /// <param name="execute">The execution logic.</param>
        /// <param name="canExecute">The execution status logic.</param>
        public RelayCommand(Action<object> execute, Predicate<object> canExecute)
        {
            if (execute == null)
                throw new ArgumentNullException("execute");

            _execute = execute;
            _canExecute = canExecute;           
        }

        #endregion // Constructors

        #region ICommand Members

        [DebuggerStepThrough]
        public bool CanExecute(object parameter)
        {
            return _canExecute == null ? true : _canExecute(parameter);
        }

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

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

        public void RaiseCanExecuteChanged()
        {
            OnCanExecuteChanged(new EventArgs());
        }

        private void OnCanExecuteChanged(EventArgs args)
        {
            if (CanExecuteChanged != null)
                CanExecuteChanged(this,args);
        }
        #endregion // ICommand Members
    }
}