调试易

请问下，关于那个socket的异步接收回调，为什么当bytesRead < StateObject.BufferSize的时候，只运行一次？
分值不多，还望高手慷慨赐教，谢！
private static void ReceiveCallback( IAsyncResult ar ) {
        try {
            // Retrieve the state object and the client socket 
            // from the asynchronous state object.
            StateObject state = (StateObject) ar.AsyncState;
            Socket client = state.workSocket;            // Read data from the remote device.
            int bytesRead = client.EndReceive(ar);            if (bytesRead > 0) {
                // There might be more data, so store the data received so far.
            state.sb.Append(Encoding.ASCII.GetString(state.buffer,0,bytesRead));                // Get the rest of the data.  bytesRead < StateObject.BufferSize的时候这句就没运行过，然后就无法继续了，因为receiveDone.Set();无法执行
                client.BeginReceive(state.buffer,0,StateObject.BufferSize,0,
                    new AsyncCallback(ReceiveCallback), state);
            } 
            else {
                // All the data has arrived; put it in response.
                if (state.sb.Length > 1) {
                    response = state.sb.ToString();
                }
                // Signal that all bytes have been received.
                receiveDone.Set();
            }
        } catch (Exception e) {
            Console.WriteLine(e.ToString());
        }
    }