Send proper api call using RestSharp to getresponse.com api - asp.net-mvc

Question

I am trying to add a contact email address to a existing campaign list named- "liakat". But I am getting a response from getresponse.com saying httpStatus 400, which you can check on the attached pitures. I have added a temporary api key, so you can test it yourself too. I am following this document from getresponse.com. Anyone who can fix this issue?
Controller:
string email = "test#gmail.com";
// Test Campaign name - "pikaa"
// "pikaa" named campaign ID->ee104303
// our api key-> 948dsdfsdfs1a017a07f3c6
var client = new RestClient("https://api.getresponse.com/v3/contacts");
var request = new RestRequest(Method.POST);
request.RequestFormat = DataFormat.Json;
var root = new RootObject();
root.campaign = new Campaign();
root.name = "Mr Men";
root.email = "test#gmail.com";
root.campaign.campaignId = "IDss6604303";
var jsBody = new JavaScriptSerializer().Serialize(root);
request.AddHeader("X-Auth-Token", "api-key 948sdfsdfsdfsdfsdfs6");
request.AddParameter("application/x-www-form-urlencoded", "email=" + email + "&campaign=ID85104303", ParameterType.RequestBody);
var response = client.Execute(request);
Model:
public class Campaign
{
public string campaignId { get; set; }
}
public class RootObject
{
public string name { get; set; }
public string email { get; set; }
public Campaign campaign { get; set; }
}

Answer 1

There is no "connection" between the Request request and the JSON Object jsBody (or root). What you're sending is a query string.
Something like
email=test#gmail.com&campaign=ID85104303
This is defined by the line:
request.AddParameter("application/x-www-form-urlencoded", "email=" + email + "&campaign=ID85104303", ParameterType.RequestBody);
If you want to send your JSON, you need to change the line to:
request.AddParameter("application/json; charset=utf-8", jsBody, ParameterType.RequestBody);
I can't tell if this will already work, but so you're at least sending the right body and you should get a successful response or at least a better error message.