Set 'Content-Type' header using RestSharp

Although this is a bit old: I ran into the same problem.. seems some attributes such as "content-type" or "date" cannot be added as parameter but are added internally. To alter the value of "content-type" I had to change the serialzer setting (altough I didn`t use it because I added a json in the body that was serialized before!)

RestClient client = new RestClient(requURI);
RestRequest request = new RestRequest(reqPath, method);
request.JsonSerializer.ContentType = "application/json; charset=utf-8";

as soon as I did this the header showed up as intended:

 System.Net Information: 0 : [5620] ConnectStream#61150033 -   Header 
 {
  Accept: application/json, application/xml, text/json, text/x-json, text/javascript, text/xml
  User-Agent: RestSharp 104.1.0.0
  Content-Type: application/json; charset=utf-8
  ...
 }

In version 105.2.3.0 I can solve the problem this way:

var client = new RestClient("https://www.example.com");
var request = new RestRequest("api/v1/records", Method.POST);
request.AddJsonBody(new { id = 1, name = "record 1" });
var response = client.Execute(request);

Old question but still top of my search - adding for completeness.

The solution provided on my blog is not tested beyond version 1.02 of RestSharp. If you submit a comment on my answer with your specific issue with my solution, I can update it.

var client = new RestClient("http://www.example.com/where/else?key=value");
var request = new RestRequest();

request.Method = Method.POST;
request.AddHeader("Accept", "application/json");
request.Parameters.Clear();
request.AddParameter("application/json", strJSONContent, ParameterType.RequestBody);

var response = client.Execute(request);