CommandBase.cs

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// Copyright (c) 2014 Silicon Studio Corp. (http://siliconstudio.co.jp)
// This file is distributed under GPL v3. See LICENSE.md for details.
using System;

using SiliconStudio.Presentation.Services;
using SiliconStudio.Presentation.ViewModel;

namespace SiliconStudio.Presentation.Commands
{
    /// <summary>
    /// An abstract class that is the base implementation of the <see cref="ICommandBase"/> interface.
    /// </summary>
    public abstract class CommandBase : DispatcherViewModel, ICommandBase
    {
        /// <summary>
        /// Backing field for the <see cref="IsEnabled"/> property.
        /// </summary>
        private bool isEnabled = true;

        /// <summary>
        /// Initializes a new instance of the <see cref="CommandBase"/> class.
        /// </summary>
        /// <param name="serviceProvider">A service provider that can provide a <see cref="IDispatcherService"/> to use for this view model.</param>
        protected CommandBase(IViewModelServiceProvider serviceProvider)
            : base(serviceProvider)
        {
        }

        /// <inheritdoc/>
        public bool IsEnabled { get { return isEnabled; } set { SetValue(ref isEnabled, value, InvokeCanExecute); } }

        /// <inheritdoc/>
        public event EventHandler CanExecuteChanged;
        
        /// <inheritdoc/>
        public virtual bool CanExecute(object parameter)
        {
            return isEnabled;
        }

        /// <inheritdoc/>
        public abstract void Execute(object parameter);

        /// <summary>
        /// Invokes <see cref="CanExecute(object)"/> with a <c>null</c> argument.
        /// </summary>
        /// <returns><c>true</c> if <see cref="CanExecute(object)"/> returned <c>true</c>, <c>false</c> otherwise.</returns>
        public bool CanExecute()
        {
            return CanExecute(null);
        }

        /// <summary>
        /// Invokes the <see cref="Execute(object)"/> command with a <c>null</c> argument.
        /// </summary>
        public void Execute()
        {
            Execute(null);
        }

        private void InvokeCanExecute()
        {
            var handler = CanExecuteChanged;
            if (handler != null)
                handler(this, EventArgs.Empty);
        }
    }
}