c# - System.Net.ProtocolViolationException 异常 C# Post 和 Getresponse

Question

对于下面的代码，我得到以下错误，

System.Net.ProtocolViolationException: You must provide a request body if you set ContentLength>0 or SendChunked==true. Do this by calling [Begin]GetRequestStream before [Begin]GetResponse.

我不确定为什么会抛出这个错误，任何意见或建议都会有所帮助

                 HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://");

                 // Set the ContentType property. 
                 request.ContentType = "application/x-www-form-urlencoded";
                 // Set the Method property to 'POST' to post data to the URI.
                 request.Method = "POST";
                 request.KeepAlive = true;
                 byte[] byteArray = Encoding.UTF8.GetBytes(postData);
                 request.ContentLength = byteArray.Length;
                 // Start the asynchronous operation.    
                 request.BeginGetRequestStream(new AsyncCallback(ReadCallback), request);

                 // Keep the main thread from continuing while the asynchronous
                 // operation completes. A real world application
                 // could do something useful such as updating its user interface. 
                 allDone.WaitOne();

                 // Get the response.
                 HttpWebResponse response = (HttpWebResponse)request.GetResponse();
                 Stream streamResponse = response.GetResponseStream();
                 StreamReader streamRead = new StreamReader(streamResponse);
                 string responseString = streamRead.ReadToEnd();
                 Console.WriteLine(responseString);
                 Console.ReadLine();
                 // Close the stream object.
                 streamResponse.Close();
                 streamRead.Close();

                 // Release the HttpWebResponse.
                 response.Close();





    private static void ReadCallback(IAsyncResult asynchronousResult)
    {

        HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;

        // End the operation.
        Stream postStream = request.EndGetRequestStream(asynchronousResult);



        // Convert the string into a byte array.
        byte[] byteArray = Encoding.UTF8.GetBytes(postData);

        // Write to the request stream.
        postStream.Write(byteArray, 0, postData.Length);
        postStream.Close();
        allDone.Set();
    }

现在我修改了我的代码以使用 HttpClient 但不起作用，

    public static async void PostAsync(String postData)
    {

        try
        {
            // Create a New HttpClient object.
            HttpClient client = new HttpClient();

            HttpResponseMessage response = await client.PostAsync("http://", new StringContent(postData));
            Console.WriteLine(response);
            //response.EnsureSuccessStatusCode();
            string responseBody = await response.Content.ReadAsStringAsync();
            // Above three lines can be replaced with new helper method in following line 
            // string body = await client.GetStringAsync(uri);

            Console.WriteLine(responseBody);

        }
        catch (HttpRequestException e)
        {
            Console.WriteLine("\nException Caught!");
            Console.WriteLine("Message :{0} ", e.Message);

        }
    }

Answer 1

错误很可能是由于您混合了异步和同步操作。 HttpWebRequest.BeginGetRequestStream 的文档说:

Your application cannot mix synchronous and asynchronous methods for a particular request. If you call the BeginGetRequestStream method, you must use the BeginGetResponse method to retrieve the response.

您的代码调用了 BeginGetRequestStream，但它调用了 GetResponse。

我认为正在发生的是它调用 BeginGetRequestStream，它开始异步写入请求流，但在主线程上它同时调用 GetResponse。所以它试图在请求格式化之前发出请求。

研究链接的 MSDN 主题中的示例并相应地修改您的代码。