Error while access token.

in Development
Hello,
I am trying to access the token for API but i am getting below Error.
{"error":"invalid_request","error_description":"The grant type was not specified in the request"}
i am using C# window application and Please find attach my sample code for your review.
Kindly consider it as urgent matter.
I am trying to access the token for API but i am getting below Error.
{"error":"invalid_request","error_description":"The grant type was not specified in the request"}
i am using C# window application and Please find attach my sample code for your review.
Kindly consider it as urgent matter.
Answers
https://cloud.merchantos.com/oauth/access_token.php
I have the same elements in the request body --- client_id, client_secret, code, and grant_type. The grant_type being authorization_code.
By the way, you should probably sanitize your examples by masking your credentials when posting on here. Otherwise you are exposing the keys to the kingdom