Automatic Implementation of the Event-Based Asynchronous Pattern

using System;
using System.Collections.Generic;
using System.Text;
using System.ComponentModel;

namespace AsyncGen
{
    /// <summary>
    /// Holds the final output of the operation.
    /// </summary>
    /// <typeparam name="TOutput">The type of the output.  If the operation has multiple outputs, a value type that encapsulates all of them.</typeparam>
	public class AsyncCompletedEventArgs<TOutput> : AsyncCompletedEventArgs
	{
        /// <summary>
        /// Constructor.
        /// </summary>
        /// <param name="output">The output of the operation.</param>
        /// <param name="error">The exception that was thrown by the operation, if it failed.</param>
        /// <param name="cancelled">A boolean value indicating whether the operation has terminated due to a cancellation request from the client.</param>
        /// <param name="userState">An object that uniquely identifies a specific invocation of the operation.</param>
		public AsyncCompletedEventArgs(TOutput output, Exception error, bool cancelled, object userState)
			: base(error, cancelled, userState)
		{
			this.output = output;
		}

        /// <summary>
        /// The output of the operation.  If the operation has multiple outputs, a <c>struct</c> that encapsulates all of them.
        /// </summary>
		public TOutput Output
		{
			get
			{
				RaiseExceptionIfNecessary();
				return output;
			}
		}

		private TOutput output;
	}

    /// <summary>
    /// Defines the signature for a handler of the completion event.
    /// </summary>
    /// <typeparam name="TOutput">The type of the output.  If the operation has multiple outputs, a value type that encapsulates all of them.</typeparam>
    public delegate void AsyncCompletedEventHandler<TOutput>(object sender, AsyncCompletedEventArgs<TOutput> args);
}