The remote server returned an error: (411) Length Required

Problem:

If you submit a post request using HttpWebRequest API without setting request body, you will receive following error message:

 System.Net.WebException: 'The remote server returned an error: (411) Length Required.'

For example, If you are making post request with this code:

 string requestedUrl = "http://localhost:13940/MyForm.aspx";
 var request = (HttpWebRequest)WebRequest.Create(requestedUrl);
 request.Method = "POST";
 request.ContentType = "application/x-www-form-urlencoded";

 using (var resp = (HttpWebResponse)request.GetResponse())
 {
  //do your work with response
 }

You will get the above error.

Solution:

• First, if you are not sending any data in request body, then using the GET method instead will be a good approach.

     string requestedUrl = "http://localhost:13940/MyForm.aspx";
     var request = (HttpWebRequest)WebRequest.Create(requestedUrl);
     request.Method = "GET";
    

• Second thing is, somehow if you are willing to use POST method and you are not sending any data, then set ContentLength property of the request object to 0, you just have to add this line:

     request.ContentLength = 0;
    

• Finally, if you need to post some data in the request body, then you must specify the data you are sending as well as length of the data. So the code segment will be like this:

     string requestedUrl = "http://localhost:13940/MyForm.aspx";
     var request = (HttpWebRequest)WebRequest.Create(requestedUrl);
     request.Method = "POST";
     request.ContentType = "application/x-www-form-urlencoded";
     
     //setup data to post
     string postData = "param1=value1¶m2=value2¶m3=value3";
     ASCIIEncoding encoding = new ASCIIEncoding();
     byte[] data = encoding.GetBytes(postData);
     //set content length
     request.ContentLength = data.Length;
     
     //write data to request stream
     var requestStream = request.GetRequestStream();
     requestStream.Write(data, 0, data.Length);
     requestStream.Close();
  
     using (var resp = (HttpWebResponse)request.GetResponse())
     {
       //do your work with response
     }
    

Any of the above change would make your request successfull.