如何实现接口返回带有空方法体的IAsyncResult

Question

如果我想继承ChannelBase IAsyncResult OnBeginOpen(TimeSpan timeout, AsyncCallback callback, object state) WCF需要我实现像IAsyncResult OnBeginOpen(TimeSpan timeout, AsyncCallback callback, object state)这样的方法。 当频道被打开时我无事可做，我宁愿把那个方法体留空。 我应该在那些空方法中作为IAsyncResult返回什么？

Answer 1

解决方法：将IAsyncResult实现添加为已完成的异步结果

internal class CompletedAsyncResult : IAsyncResult
{
    public CompletedAsyncResult(object state)
    {
        this.AsyncState = state;
    }

    public object AsyncState { get; set; }

    public WaitHandle AsyncWaitHandle => new ManualResetEvent(true);

    public bool CompletedSynchronously => true;

    public bool IsCompleted => true;
}

并使用像

protected override IAsyncResult OnBeginOpen(TimeSpan timeout, AsyncCallback callback, object state)
{
    var result = new CompletedAsyncResult(state);
    callback?.Invoke(result);
    return result;
}

Answer 2

根据经验，你根本不应该有空的方法。 如果ChannelBase有一个你不需要的抽象方法，你应该提供合理的覆盖，即使你现在不需要它，或者从中抛出NotSupportedException ，异常消息解释了为什么不支持这种方法：

public override IAsyncResult OnBeginOpen(TimeSpan timeout, AsyncCallback callback, object state) 
{
    throw new NotSupportedException("OnBeginOpen is not supported because...");
}