使用 WCF 无法掌握异步模式

Question

我正在开发一个 WCF 服务，在该服务上，服务器能够对来自文件的特定字节的客户端请求进行异步调用。

回调合约：

public interface IControlChannelCallback
    {
        [...]

        [OperationContract(AsyncPattern = true)]
        IAsyncResult BeginGetRemoteFile(string filename, byte[] buffer, int position, int count, AsyncCallback callback, object state);

        int EndGetRemoteFile(IAsyncResult ar);
    }

实施：

public IAsyncResult BeginGetRemoteFile(string filename, byte[] buffer, int position, int count, AsyncCallback callback,
            object state)
        {
            var task = Task<int>.Factory.StartNew(x =>
            {
                using (var fileStream = new FileStream(filename, FileMode.Open))
                {
                    fileStream.Position = position;

                    return fileStream.Read(buffer, 0, count);
                }
            }, state);

            return task.ContinueWith(x => callback(task));
        }

        public int EndGetRemoteFile(IAsyncResult ar)
        {
            var task = (Task<int>) ar;

            return task.Result;
        }

状态对象：

public class ServiceStreamReaderStateObject
    {
        public const int BufferSize = 1024;

        public byte[] Buffer { get; private set; }

        public int TotalRead { get; set; }

        public ServiceStreamReaderStateObject()
        {
            Buffer = new byte[BufferSize];
        }
    }

服务使用情况：

private void Download()
{
    var state = new ServiceStreamReaderStateObject();

    _client.Callback.BeginGetRemoteFile(@"F:\1313363989488.jpg", state.Buffer, 0,      state.Buffer.Length, RealCallback, state);
}

private void RealCallback(IAsyncResult ar)
        {
            var state = (ServiceStreamReaderStateObject) ar.AsyncState;

            var totalRead = _client.Callback.EndGetRemoteFile(ar);
        }

似乎一切正常，当我调用EndGetRemoteFile 方法时，它返回1024，这是应该读取多少字节，但问题是封装在状态对象ServiceStreamReaderStateObject 上的缓冲区为空（已满零）。

我不明白我做错了什么，按照我的逻辑缓冲区应该充满数据，我在这里做错了什么？

Answer 1

只是预感：你能去掉“ServiceStreamReaderStateObject”的Buffer属性上的“private”访问修饰符吗

public class ServiceStreamReaderStateObject
{
    public const int BufferSize = 1024;

    public byte[] Buffer { get; set; }

    public int TotalRead { get; set; }

    public ServiceStreamReaderStateObject()
    {
        Buffer = new byte[BufferSize];
    }