I got authkey from link. But GetResponse always returns error 400 bad request.

Can somebody suggest what's wrong with my code? strID is request ID.

2.         Dim sData As String
3.         Dim request As WebRequest = WebRequest.Create("http://sdpondemand.manageengine.com/api/json/request/" & strID)
4.         Dim myProxy As New WebProxy("xxxxxxx", 8080)
5.         myProxy.BypassProxyOnLocal = True
6.         request.Proxy = myProxy
7. 
   
8.         request.Method = "POST"
9.         request.ContentType = "application/x-www-form-urlencoded"
10. 
    
11.         sData = "scope=sdpodapi"
12.         sData = sData & "&authtoken=" & AuthKey
13.         sData = sData & "&OPERATION_NAME=GET_REQUEST"
14. 
    
15.         Dim encoding As New System.Text.UTF8Encoding()
16.         Dim bytes As Byte() = encoding.GetBytes(sData)
17. 
    
18.         request.ContentLength = bytes.Length
19.         Try
20.             Dim requestStream As Stream = request.GetRequestStream()
21.             requestStream.Write(bytes, 0, bytes.Length)
22.             requestStream.Close()
23.             requestStream.Dispose()
24. 
    
25.             Dim res As WebResponse = request.GetResponse()
26.             Dim resStream As Stream = res.GetResponseStream()
27.             Dim sr As New StreamReader(resStream, encoding)
28.             Get_Request = sr.ReadToEnd()
29. 
    
30.         Catch ex As Exception
31.             Get_Request = ex.Message.ToString
32.         End Try