我查看了.NET Reference Source，它会抛出异常。
代码：
[HostProtection(ExternalThreading=true)]
public IAsyncResult BeginReceive(byte[] buffer, int offset, int size, SocketFlags socketFlags, AsyncCallback callback, object state)
{
SocketError errorCode;
IAsyncResult result = BeginReceive(buffer, offset, size, socketFlags, out errorCode, callback, state);
if(errorCode != SocketError.Success && errorCode !=SocketError.IOPending){
throw new SocketException(errorCode);
}
return result;
}
在从名为 DoBeginReceive 的方法中的 Begin 重载调用的方法中，此方法调用此代码。错误代码是使用 out 关键字传递的，因此它正是传递回来的内容。
errorCode = UnsafeNclNativeMethods.OSSOCK.WSARecv(
m_Handle,
ref asyncResult.m_SingleBuffer,
1,
out bytesTransferred,
ref socketFlags,
asyncResult.OverlappedHandle,
IntPtr.Zero);
编辑：对于 .NET CF：
如 OP 所述
这是开始接收
public IAsyncResult BeginReceive(byte[] buffer, int offset, int size, SocketFlags socketFlags, AsyncCallback callback, object state)
{
this.throwIfDisposed();
if (buffer == null)
{
throw new ArgumentNullException("buffer");
}
if (offset < 0)
{
throw new ArgumentOutOfRangeException("offset");
}
if (size < 0)
{
throw new ArgumentOutOfRangeException("size");
}
if (buffer.Length < (offset + size))
{
throw new ArgumentOutOfRangeException("", SR.GetString(0x41, new object[0]));
}
ReceiveAsyncRequest req = new ReceiveAsyncRequest(this, buffer, offset, size, socketFlags, callback, state);
this.addReadRequest(req);
return req;
}
addReadRequest 这样做：
private void addReadRequest(AsyncRequest req)
{
lock (this)
{
if (this.m_readHead == null)
{
if (!startWorker(req))
{
req.InvokeCallback(false, new OutOfMemoryException(SR.GetString(0x42, new object[0])));
}
else
{
this.m_readHead = req;
}
}
else
{
AsyncRequest readHead = this.m_readHead;
while (readHead.m_next != null)
{
readHead = readHead.m_next;
}
readHead.m_next = req;
}
}
}
startWorker 会这样做：
private static bool startWorker(AsyncRequest req)
{
WorkerThread thread = new WorkerThread(req);
if (!ThreadPool.QueueUserWorkItem(new WaitCallback(thread.doWorkI)))
{
return false;
}
return true;
}
线程调用ReceiveAsyncRequest的doWork调用ReceiveAsyncRequest的doRequest，它调用handleRequest，handleRequest又调用ReceiveAsyncRequest上的doRequest。
ReceiveAsyncRequest 方法的 doRequest 如下所示：
protected override object doRequest()
{
return base.m_socket.ReceiveNoCheck(this.m_readBuffer, this.m_index, this.m_size, this.m_flags);
}
在 ReceiveFromNoCheck 中抛出异常：
internal int ReceiveFromNoCheck(byte[] buffer, int index, int request, SocketFlags flags)
{
this.throwIfDisposed();
int rc = 0;
int num2 = OSSOCK.recv(this.handle, buffer, index, request, (int) flags, ref rc);
if(num2 < 0)
{
throw new SocketException(rc);
}
return num2;
}
如果 AsyncResults 运行 sychronously，它将抛出异常。但是，如果它是 ThreadPool 的一部分，则只会抛出异常并kill the application。