I cant upload files in c#

API
1

i cant upload files in c#

2

This is my code using RestSharp

using RestSharp;
using System;
using System.Collections.Generic;
using System.IO;
using System.Threading.Tasks;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;

namespace GRT.PipedriveApi.EntityServices
{
    public class FileEntityService<TFile> : PagingEntityService<TFile>
        where TFile : File
    {
        public FileEntityService(IPipedriveClient client) : base(client, "files")
        {
        }
        public async Task<bool> AddFileToDeal(int DealId, string FileName)
        {
            var request = new RestRequest("files", Method.POST);
            
            request.AddParameter("deal_id", DealId.ToString(), ParameterType.GetOrPost);
            request.AddFile("file", FileName, "multipart/form-data");
            try
            {
                string response = await _client.ExecuteRequestNoPaging(request);
                JObject AddedFile = JObject.Parse(response);
                string _success = (string)AddedFile["success"];
                if (_success.ToLower() == "true")
                {
                    return true;
                }
                else
                {
                    throw new Exception("Unable to add file - " + (string)AddedFile["error"]);
                }
            }
            catch (Exception ex)
            {
                return (false);   
            }


        }
    }
}