当我点击谷歌对话流的端点但相同的谷歌对话流端点在邮递员中工作时，在 c# 中出现错误

我在 PostMan 中使用这个端点：-

https://api.dialogflow.com/v1/query?v=20150910

我发送的这个 JSON 字符串：-

{"query":"flights from NYC to Vadodara","sessionId":"6b9d4676-2a71-4c64-a562-8c08f198c623","lang":"pt-BR","resetContexts":false}

我正在邮递员中设置内容类型和授权。

所有这些东西都在邮递员中完美运行，但问题是当我使用 c# 代码点击此端点时，它给了我这个错误：-

我得到的错误：-

{
  "id": "7b0ac743-58ea-4d61-a41d-a299f086a816",
  "timestamp": "2018-06-04T15:30:25.873Z",
  "lang": "en",
  "status": {
    "code": 400,
    "errorType": "bad_request",
    "errorDetails": "Invalid request content type, expecting \"multipart/form-data\" or \"application/json; charset\u003dutf-8."
  }
}

这是我的代码：

using ApiAi.Models;
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication6
{
    class Program
    {
        static void Main(string[] args)
        {
            HttpClient http = new HttpClient();

            http.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));//ACCEPT header
            http.DefaultRequestHeaders.Add("ContentType", "application/json; charset=utf-8");
            http.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", "xxx");

            var response = http.PostAsync("https://api.dialogflow.com/v1/query?v=20150910", new StringContent(new Program().getSessionID(new ConfigModel { AccesTokenClient = "xxx" }, "flights from NYC to Vadodara"))).Result.Content.ReadAsStringAsync().Result;
        }
        public string getSessionID(ConfigModel config, string message)
        {
            var requestData = new RequestModel
            {
                query = message,
                sessionId = (config.SessionId ?? Guid.NewGuid()).ToString(),
                lang = "pt-BR"
            };
            return JsonConvert.SerializeObject(requestData);
        }
    }
    public class RequestModel
    {
        public string query { get; set; }
        public string sessionId { get; set; }
        public string lang { get; set; }
        public bool resetContexts { get; set; }
    }
}








//  
// Copyright (c) 2017 Nick Rimmer. All rights reserved.  
// Licensed under the MIT License. See LICENSE file in the project root for full license information.  
//

using ApiAi.Enums;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ApiAi.Models
{
    /// <summary>
    /// Services configuration
    /// </summary>
    public class ConfigModel
    {
        #region magic
        internal static string 
            BaseUrl = @"https://api.dialogflow.com/v1",
            VersionCode = @"20150910";

        #endregion

        /// <summary>
        /// Each API request requires authentication to identify the agent that is responsible for making the request. Authentication is provided through an access token.
        /// The developer access token is used for managing entities and intents.
        /// </summary>
        public string AccesTokenDeveloper { get; set; }

        /// <summary>
        /// Each API request requires authentication to identify the agent that is responsible for making the request. Authentication is provided through an access token.
        /// The client access token is used for making queries.
        /// </summary>
        public string AccesTokenClient { get; set; }

        /// <summary>
        /// Specifed language in your Api.ai agent
        /// </summary>
        public LanguagesEnum Language { get; set; }

        /// <summary>
        /// Timezone requests parameter
        /// </summary>
        public string TimeZone { get; set; } = System.TimeZone.CurrentTimeZone.StandardName;

        /// <summary>
        /// Session ID for request
        /// </summary>
        public object SessionId { get; set; } = Guid.NewGuid();
    }
}

这是我正在使用的代码。提前致谢。