RelayCommand.cs

using System;
using System.Windows.Input;

namespace Jason.Down.Blog.MutliImageAddinDemo.Command
{
    /// <summary>
    ///     The <see cref="RelayCommand" /> simply invokes delegates for given command functionality.
    ///     <see cref="CanExecute" /> returns true by default.
    /// </summary>
    [Serializable]
    public class RelayCommand : ICommand
    {
        private readonly Func<bool> _canExecute;
        private readonly Action _execute;
        private readonly Action<Object> _executeParam;

        /// <summary>
        ///     Initializes a new instance of the <see cref="RelayCommand" /> class.
        ///     This command can always execute (no predicate to control execution logic).
        /// </summary>
        /// <param name="execute">The execute.</param>
        public RelayCommand(Action<Object> execute)
            : this(execute, null)
        {
        }

        /// <summary>
        ///     Initializes a new instance of the <see cref="RelayCommand" /> class.
        /// </summary>
        /// <param name="execute">The execute command.</param>
        /// <param name="canExecute">A predicate that controls whether or not the command can execute.</param>
        /// <exception cref="System.ArgumentNullException">execute</exception>
        public RelayCommand(Action<object> execute, Func<bool> canExecute)
        {
            if (execute == null)
            {
                throw new ArgumentNullException("execute");
            }

            _executeParam = execute;
            _canExecute = canExecute;
        }

        /// <summary>
        ///     Initializes a new instance of the <see cref="RelayCommand" /> class.
        /// </summary>
        /// <param name="execute">The execute command.</param>
        public RelayCommand(Action execute)
            : this(execute, null)
        {
        }

        /// <summary>
        ///     Initializes a new instance of the <see cref="RelayCommand" /> class.
        /// </summary>
        /// <param name="execute">The execute command.</param>
        /// <param name="canExecute">A predicate that controls whether or not the command can execute.</param>
        /// <exception cref="System.ArgumentNullException">execute</exception>
        public RelayCommand(Action execute, Func<bool> canExecute)
        {
            if (execute == null)
            {
                throw new ArgumentNullException("execute");
            }

            _execute = execute;
            _canExecute = canExecute;
        }

        /// <summary>
        ///     Defines the method that determines whether the command can execute in its current state.
        /// </summary>
        /// <param name="parameter">Data used by the command.  If the command does not require data to be passed, this object can be set to null.</param>
        /// <returns>
        ///     <c>true</c> if this command can be executed; otherwise, <c>false</c>.
        /// </returns>
        public bool CanExecute(object parameter)
        {
            if (_canExecute != null)
            {
                return _canExecute();
            }

            return true;
        }

        /// <summary>
        ///     Defines the method to be called when the command is invoked.
        /// </summary>
        /// <param name="parameter">Data used by the command. If the command does not require data to be passed, this object can be set to null.</param>
        public void Execute(object parameter)
        {
            if (_execute != null)
            {
                _execute();
            }
            else if (_executeParam != null)
            {
                _executeParam(parameter);
            }
        }

        /// <summary>
        ///     Occurs when changes occur that affect whether or not the command should execute.
        /// </summary>
        public event EventHandler CanExecuteChanged
        {
            add { CommandManager.RequerySuggested += value; }
            remove { CommandManager.RequerySuggested -= value; }
        }
    }
}