(417) Expectation Failed - Twitter and .net aren't nice to each other

I have been writing applications that work with the Twitter API for a few years now. It's pretty simple, but if you don't know where to start, you could run into some trouble.

The first big problem I ran into was the "(417) Expectation Failed" error that Twitter started to return one day out of the blue.

I was using the Yedda dll to do all of my interaction with the Twitter API, and I didn't really know how it worked, so I went through it for a while, getting to know it.

I then got a little frustrated with it, and wrote my own Twitter class to use. I still had the "(417) Expectation Failed" error coming back when I tried to post to the API.

After a little research, I found out that the API no longer likes the HTTP header with the "100-Continue" value.

To fix this, I needed to add the following line of code to my method:

"request.ServicePoint.Expect100Continue = false;"

This fixed my Post code, and I was happy for a little while.

Then my world came crashing down, and the error came back. Again, it was without warning, and I was left scratching my head.

I went back to Google, and after a few hours searching, I found the solution.

This is how I did it:

     public static String ExecutePostCommand(String url, String UserName, String Password, String data)  
     {  
       HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);   
       request.ServicePoint.Expect100Continue = false;  
       try  
       {  
         if (!String.IsNullOrEmpty(UserName) && !String.IsNullOrEmpty(Password))  
         {  
           request.Credentials = new NetworkCredential(UserName, Password);  
           request.ContentType = "application/x-www-form-urlencoded";  
           request.Method = "POST";  
           byte[] bytes = Encoding.UTF8.GetBytes(data);  
           request.ContentLength = bytes.Length;  
           using (Stream requestStream = request.GetRequestStream())  
           {  
             requestStream.Write(bytes, 0, bytes.Length);  
             //HttpWebResponse response = (HttpWebResponse)request.GetResponse()  
             using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())  
             {  
               using (StreamReader reader = new StreamReader(response.GetResponseStream()))  
               {  
                 return reader.ReadToEnd();  
               }  
             }  
           }  
         }  
       }  
       catch (WebException ex)  
       {  
         if (ex.Response is HttpWebResponse)  
         {  
           if ((ex.Response as HttpWebResponse).StatusCode == HttpStatusCode.NotFound)  
           {  
             return null;  
           }  
         }  
         throw ex;  
       }  
       return null;  
     }  

You will see that I am using a HTTPWebRequest in the code. The original Yedda dll used a WebRequest instead.


My code works now, and I'm happy, that's until the next little/big API change that makes me pull my already thinning hair out.