What is the difference between
request.ContentType = "application/json; charset=utf-8";
and
webRequest.ContentType = "application/x-www-form-urlencoded";
The first case is telling the web server that you are posting JSON data as in:
{"Name": "John Smith", "Age": 23}
The second case is telling the web server that you will be encoding the parameters in the URL:
Name=John+Smith&Age=23