title: Restsharp Exception The URI prefix is not recognized
body: <p>I'm getting an exception from RestSharp <code>The URI prefix is not recognized</code> and can't figure out why.</p>
  
  <p>Parameters</p>
  
  <p><code>requestBody</code> is just a POCO</p>
  
  <p><code>domain</code> is <code>some.company.com</code> and </p>
  
  <p><code>_config.AddPersonEndpoint</code> is <code>api/person/add</code></p>
  
  <pre><code>public PersonResponse AddPerson(PersonRequest requestBody, string domain)
  {
      var client = new RestClient(domain);
  
      var request = new RestRequest(_config.AddPersonEndpoint, Method.POST);
      request.RequestFormat = DataFormat.Json;
      request.AddBody(requestBody);
  
      var response = client.Execute&lt;PersonResponse&gt;(request);
  
      if (response.ErrorException != null)
          throw response.ErrorException;
  
      if (response.ErrorMessage != null)
          throw new PortalConnectivityException(response.ErrorMessage);
  
      if (!string.IsNullOrEmpty(response.Data.ErrorMessage))
          throw new PortalException(response.Data.ErrorMessage);
  
      return response.Data;
  
  }
  </code></pre>