创建以Json为内容的HttpRequestMessage

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

namespace ConsoleApplication4
{
    class Program
    {
        static void Main(string[] args)
        {
            CreateHttpRequestMessage();
        }

        public static HttpRequestMessage CreateHttpRequestMessage()
        {
            HttpRequestMessage requestMessage = new HttpRequestMessage();
            JsonHSBCMailMessage JsonHsbcMailMessage = new JsonHSBCMailMessage
            {
                Host = "host111",
                Port = 1231312312
    
            };

            string Body = JsonConvert.SerializeObject(JsonHsbcMailMessage);
            requestMessage.Content = new StringContent(Body, Encoding.UTF8, "application/x-www-form-urlencoded");

            return requestMessage;
        }
    }

    class JsonHSBCMailMessage
    {
        public string Host
        {
            get; set;
        }

        public int Port
        {
            get; set;
        }

    }
}

* Newtonsoft.Json 需要自己下载并加载到引用列表