RelayCommand.cs

using System;
using System.Windows.Input;

namespace LibVLCSharp.UWP.Sample
{
    /// <summary>
    /// A command whose sole purpose is to relay its functionality to other objects by invoking delegates
    /// </summary>
    public class RelayCommand<T> : ICommand
    {
        /// <summary>
        /// Occurs when changes occur that affect whether or not the command should execute
        /// </summary>
        public event EventHandler CanExecuteChanged;

        /// <summary>
        /// Creates a new command
        /// </summary>
        /// <param name="executeAction">the execution logic</param>
        public RelayCommand(Action<T> executeAction)
        {
            ExecuteAction = executeAction;
        }

        private Action<T> ExecuteAction { get; }

        /// <summary>
        /// Raises the <see cref="CanExecuteChanged" /> event
        /// </summary>
        public void RaiseCanExecuteChanged()
        {
            CanExecuteChanged?.Invoke(this, EventArgs.Empty);
        }

        /// <summary>
        /// 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>true</returns>
        public bool CanExecute(object parameter)
        {
            return true;
        }

        /// <summary>
        /// Executes the <see cref="RelayCommand"/>
        /// </summary>
        /// <param name="parameter">data used by the command</param>
        public void Execute(object parameter)
        {
            ExecuteAction?.Invoke((T)parameter);
        }
    }


    public class RelayCommand : ICommand
    {
        private readonly Action _execute;
        private readonly Func<bool> _canExecute;

        /// <summary>
        /// Raised when RaiseCanExecuteChanged is called.
        /// </summary>
        public event EventHandler CanExecuteChanged;

        /// <summary>
        /// Creates a new command that can always execute.
        /// </summary>
        /// <param name="execute">The execution logic.</param>
        public RelayCommand(Action 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 execute, Func<bool> canExecute)
        {
            if (execute == null)
                throw new ArgumentNullException("execute");
            _execute = execute;
            _canExecute = canExecute;
        }

        /// <summary>
        /// Determines whether this <see cref="RelayCommand"/> 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>true if this command can be executed; otherwise, false.</returns>
        public bool CanExecute(object parameter)
        {
            return _canExecute == null ? true : _canExecute();
        }

        /// <summary>
        /// Executes the <see cref="RelayCommand"/> on the current command target.
        /// </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)
        {
            _execute();
        }

        /// <summary>
        /// Method used to raise the <see cref="CanExecuteChanged"/> event
        /// to indicate that the return value of the <see cref="CanExecute"/>
        /// method has changed.
        /// </summary>
        public void RaiseCanExecuteChanged()
        {
            var handler = CanExecuteChanged;
            if (handler != null)
            {
                handler(this, EventArgs.Empty);
            }
        }
    }
}