curl -H "Authorization: Bearer API_KEY" -H "Content-Type: application/json" -X _
  POST -i https://api.1fichier.com/v1/file/ls.cgi -d _
  '{"folder_id":0,"pretty":1}'

using (var httpClient = new HttpClient())
{
    using (var request = new HttpRequestMessage(new HttpMethod("POST"), _
      "https://api.1fichier.com/v1/file/ls.cgi"))
    {
        request.Headers.TryAddWithoutValidation("Authorization", "Bearer" & _
          "API_KEY"); 
 
        request.Content = new StringContent("{\"folder_id\":0,\"pretty\":1}");
        request.Content.Headers.ContentType = MediaTypeHeaderValue.Parse( _
          "application/json"); 
 
        var response = await httpClient.SendAsync(request);
    }
}