c# (Connect)Stream readasync 无限读取 0

Question

给定以下从 Stream 异步读取的方法（简化）：

private async void WaitForIncomingMessagesAsync()
{
    var responseStream = WebRequest.Create("some url").GetResponse().GetResponseStream(); // onle here in the example

    var buffer = new byte[8192];
    var stringBuilder = new StringBuilder();
    while (IsRunning /*set by other parts of the program*/)
    {
        int receivedDataCount;
        do
        {
            receivedDataCount = await responseStream.ReadAsync(buffer, 0, buffer.Length);
            if (receivedDataCount != 0)
            {
                stringBuilder.Append(Encoding.ASCII.GetString(buffer, 0, receivedDataCount));
            }
        } while (receivedDataCount > 0);

        var receivedDataJson = stringBuilder.ToString();
        Array.Clear(buffer, 0, buffer.Length);
        stringBuilder.Clear();
    }
}

在我收到流中的第一个 'message' 之前，这一切正常。从那以后，它将不再停在 await 因为它总是读取 0.

流本身必须始终保持打开状态。

我错过了什么？我是否必须重置流、刷新它或将位置设置回 0？

responseStream.Position = 0; 或 responseStream.Seek(0, SeekOrigin.Begin)

throws NotSupportedException

Answer 1

根据您的代码，我假设您希望在每次外循环运行时阅读新消息。如果是这样，那么您的 GetResponse 应该在外循环内，否则一旦您的内部循环完成对流的迭代，您将永远不会读取新数据。

private async void WaitForIncomingMessagesAsync()
{
    var buffer = new byte[8192];
    var stringBuilder = new StringBuilder();
    while (IsRunning)
    {
        using (var responseStream = WebRequest.Create("some url").GetResponse().GetResponseStream())
        {
            int receivedDataCount;
            do
            {
                receivedDataCount = await responseStream.ReadAsync(buffer, 0, buffer.Length);
                if (receivedDataCount != 0)
                {
                    stringBuilder.Append(Encoding.ASCII.GetString(buffer, 0, receivedDataCount));
                }
            } while (receivedDataCount > 0);
        }
        var receivedDataJson = stringBuilder.ToString();
        Array.Clear(buffer, 0, buffer.Length);
        stringBuilder.Clear();
    }
}

我还使用 (..) {} 构造将您的响应流包装到 中，因此您不必担心手动关闭和处理它。

c# (Connect)Stream readasync 无限读取 0

c# (Connect)Stream readasync reads 0 infinitely

c#

buffer

asynchronous

stream