将异步编程模型(开始/结束方法)转换为基于事件的异步模型?

见 "Async without the pain" 关于这方面的一些想法:所提供的代码使用回调方法,但是如果将其放到实例上,事件就足够简单了。

public static void RunAsync<T>(
    Func<AsyncCallback, object, IAsyncResult> begin,
    Func<IAsyncResult, T> end,
    Action<Func<T>> callback) {
    begin(ar => {
        T result;
        try {
            result = end(ar); // ensure end called
            callback(() => result);
        } catch (Exception ex) {
            callback(() => { throw ex; });
        }
    }, null);
}

http://asyncfunc.codeplex.com

代码如下所示:

public class Original
{
    public ResultType Operation(ParamType param){...}
    public IAsyncResult BeginOperation(ParamType param, AsyncCallback callback, object state){...}
    public ResultType EndOperation(IAsyncResult ar){...}
}

public class Wrapper
{
    private AsyncFunc<ParamType, ResultType> _operation;
    private Original _original;

    public Wrapper(Original original)
    {
        _original = original;
        _operation = AsyncFunc<ParamType, ResultType>(_original.Operation);
    }

    public ResultType Operation(ParamType param)
    {
        return _original.Operation(param);
    }

    public void OperationAsync(ParamType param)
    {
        _operation.InvokeAsync(param)
    }

    public event AsyncFuncCompletedEventHandler<ResultType> OperationCompleted      
      {
        add { _operation.Completed += value; }
        remove { _operation.Completed -= value; }
    }
}

注意在这种方法中 . 可以用AsyncFunc泛型类型替换它们:

OperationCompletedEventArgs -> ResultType
OperationCompletedEventHandler -> AsyncFuncCompletedEventHandler<ResultType>

有关更高级的方案,请转到AsyncFunc主页。有一些视频和样本。