Generic AsyncCompletedEventArgs class for simple EAP async return values

AsyncCompletedEventArgs.cs

namespace System.ComponentModel
{
    public class AsyncCompletedEventArgs<T> : AsyncCompletedEventArgs
    {
        private T result;

        public AsyncCompletedEventArgs(Exception error, bool cancelled, object userState)
            : base(error, cancelled, userState)
        { }

        public AsyncCompletedEventArgs(T result, object userState)
            : base(null, false, userState)
        {
            this.result = result;
        }

        public T Result
        {
            get { return result; }
        }
    }
}

Update: forgot that having the result constructor on its own would hide the base constructor. That problem's been fixed with this newer version.