在异步回调中从网络流读取缓冲区

Question

另请参阅MSDN 中的 Understanding the NetworkStream.EndRead() 示例。

我正在尝试使用BeginRead和EndRead方法从 NetworkStream 异步读取(具体来说，我想打开 NetworkStream，执行各种其他任务，然后处理在 NetworkStream 上接收的数据)。EndRead的 MSDN 示例(此处)存在各种问题，并且无法正常工作，如链接问题中所述。 该问题的答案显示了基本代码应该如何构建，但它不包括回调中从NetworkStream实际读取的数据。

在回调函数中，如何将从网络流读取的数据传输到缓冲区中？

编辑

这是原始的 MSDN 示例。

public static void myReadCallBack(IAsyncResult ar )
{
NetworkStream myNetworkStream = (NetworkStream)ar.AsyncState;
byte[] myReadBuffer = new byte[1024];
String myCompleteMessage = "";
int numberOfBytesRead;
numberOfBytesRead = myNetworkStream.EndRead(ar);
myCompleteMessage = String.Concat(myCompleteMessage,Encoding.ASCII.GetString(myReadBuffer, 0, numberOfBytesRead));    
// message received may be larger than buffer size so loop through until you have it all.
while(myNetworkStream.DataAvailable)
{
myNetworkStream.BeginRead(myReadBuffer, 0, myReadBuffer.Length, new AsyncCallback(NetworkStream_ASync_Send_Receive.myReadCallBack), myNetworkStream);  
}
// Print out the received message to the console.
Console.WriteLine("You received the following message : " + myCompleteMessage);
}

此示例的基本问题是没有数据从 NetworkStream 传输到myReadBuffer.

编辑 1

感谢Dmytro Mukalov，以下代码有效：

internal class CallbackArgs
{
public NetworkStream Stream { get; set; }
public byte[] Buffer { get; set; }
public CallbackArgs(NetworkStream stream, byte[] buffer)
{
Stream = stream;
Buffer = buffer;
}
}
//  In the caller:
//  (Create and open thisNetworkStream, and check thisNetworkStream.CanRead)
byte[] thisReadBuffer = new byte[1024];
CallbackArgs args = new CallbackArgs(thisNetworkStream, thisReadBuffer);
thisNetworkStream.BeginRead(thisReadBuffer, 0, thisReadBuffer.Length, new AsyncCallback(myReadCallBack), args);
//  The callback function:
public static void myReadCallBack(IAsyncResult ar)
{
CallbackArgs args = (CallbackArgs)ar.AsyncState;
NetworkStream myNetworkStream = args.Stream;
byte[] myReadBuffer = args.Buffer;
//  myReadBuffer now contains the data read from the network stream.
int bytesRead = myNetworkStream.EndRead(ar);
//  Do work on myReadBuffer, etc.
}

Answer 1

执行回调时，数据已经传输到传递给前面BeginRead调用的缓冲区中。给定示例的问题在于它尝试使用本地myReadBuffer缓冲区来读取初始消息。相反，您应该使传递给BeginRead缓冲区可用于EndRead。您可以通过使其成为此缓冲区类的实例成员，将其与NetworkStream一起作为BeginRead的参数传递state，在某个将启动读取循环的方法中使用闭包变量等来做到这一点。