Как отключить encode в WebClient UploadValues?

using (var client = new HttpClient())
{
  var url = new Uri("http://site.com/index.php?199|&param=1", true);
  var data = new StringBuilder();
  data.AppendLine("abc=199|");

  using (var content = new StringContent(data.ToString(), Encoding.UTF8, "application/x-www-form-urlencoded"))
  {
    using (var request = new HttpRequestMessage(HttpMethod.Post, url))
    {
      request.Content = content;

      using (var response = client.SendAsync(request).Result)
      {
        response.EnsureSuccessStatusCode();

        // var result = await response.Content.ReadAsStringAsync();
        var result = response.Content.ReadAsStringAsync().Result;
      }
    }
  }
}