[Solved-3 Solutions] HTTP POST Returns Error: 417 “Expectation Failed.”




Error Description:

    • When we try to POST to a URL it results in the following exception:

    The remote server returned an error: (417) Expectation Failed.

    • Here's a sample code:
    var client = new WebClient();
    
    var postData = new NameValueCollection();
    postData.Add("postParamName", "postParamValue");
    
    byte[] responseBytes = client.UploadValues("http://...", postData);
    string response = Encoding.UTF8.GetString(responseBytes); // (417) Expectation Failed.
    
    click below button to copy the code. By - C# tutorial - team

    Solution 1:

      • System.Net.HttpWebRequest adds the header 'HTTP header "Expect: 100-Continue"' to every request unless you explicitly ask it not to by setting this static property to false:
      System.Net.ServicePointManager.Expect100Continue = false;
      
      click below button to copy the code. By - C# tutorial - team
      • Some servers choke on that header and send back the 417 error you're seeing.
      • Give that a try.

      Solution 2:

          <system.net>
              <settings>
                  <servicePointManager expect100Continue="false" />
              </settings>
          </system.net>
          
          
          click below button to copy the code. By - C# tutorial - team

          Solution 3:

            • If you are using "HttpClient", and you don't want to use global configuration to affect all your program you can use:
            HttpClientHandler httpClientHandler = new HttpClientHandler();
             httpClient.DefaultRequestHeaders.ExpectContinue = false;
            
            click below button to copy the code. By - C# tutorial - team
            • I you are using "WebClient" I think you can try to remove this header by calling:
            var client = new WebClient();
             client.Headers.Remove(HttpRequestHeader.Expect);
            
            
            click below button to copy the code. By - C# tutorial - team

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