C# 使用HttpClient发布自定义类型

我有一个自定义dto类：

public class myObject
{
    public string Id { get; set; }
    public string Name { get; set; }
}

以及使用Web Api（4.5.net framework）的控制器

客户端只有4.0.net framework，因此我无法使用PostAsJsonAsync（）方法。将对象从客户端传递到服务器的解决方案是什么

我试过以下方法：

var response = Client.SendAsync(new HttpRequestMessage<myObject>(objectTest)).Result;

---

难道不能使用Newtonsoft.Json库吗？

当然可以。只需像这样为自己创建一个新的HttpContent类

  public class JsonContent : HttpContent
    {

        private readonly MemoryStream _Stream = new MemoryStream();

        public JsonContent(object value)
        {

            var jw = new JsonTextWriter(new StreamWriter(_Stream)) {Formatting = Formatting.Indented};
            var serializer = new JsonSerializer();
            serializer.Serialize(jw, value);
            jw.Flush();
            _Stream.Position = 0;

        }
        protected override Task SerializeToStreamAsync(Stream stream, TransportContext context)
        {
            _Stream.CopyTo(stream);
            var tcs = new TaskCompletionSource<object>();
            tcs.SetResult(null);
            return tcs.Task;
        }

        protected override bool TryComputeLength(out long length)
        {
            length = _Stream.Length;
            return true;
        }
    }

---

创建一个继承自HttpContent的类，该类为您提供网络流，您可以直接向其写入而不使用memoryStream

大概是这样的：

using System;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;
using Newtonsoft.Json;

namespace Http.Helper.Extensions
{
    public class JsonHttpContentSerializer : HttpContent
    {

        private object Value { get; set; }

        public JsonHttpContentSerializer(Object value)
        {
            this.Value = value;
        }


        protected override async Task SerializeToStreamAsync(Stream stream, TransportContext context)
        {
            using (var streamWriter = new StreamWriter(stream, new UTF8Encoding(false), 1024, true))
            {
                using (var jsonTextWriter = new JsonTextWriter(streamWriter) { Formatting = Formatting.None })
                {
                    var jsonSerializer = new JsonSerializer();
                    jsonSerializer.Serialize(jsonTextWriter, Value);
                    jsonTextWriter.Flush();
                }
            }

        }

        protected override bool TryComputeLength(out long length)
        {
            length = -1;
            return false;
        }

    }
}

你会喜欢它吗

var jsonSerializeContent = new JsonHttpContentSerializer(someContent);
httpRequestMessage.Content = jsonSerializeContent;

---

谢谢你的解决方案。我不确定SerializeToStreamAsync做什么，TaskCompletionSource需要结果值的类型。是输入对象还是输出对象？@user1542666很抱歉，我不得不在运行中将if从.net45转换为4.0，并且忘记了

。SerializeToStream方法将在HttpClient需要时将缓冲流复制到网络流。为什么要使用缓冲流？我们可以利用网络流将对象直接写入其中？像这样的<代码>受保护的重写异步任务SerializeToStreamAsync（Stream，TransportContext上下文）{StreamWriter=new StreamWriter（Stream，new UTF8Encoding（false））；JsonTextWriter=new JsonTextWriter（StreamWriter）{Formatting=Formatting.None}；JsonSerializer.Serialize（JsonTextWriter，Value）；//JsonTextWriter.Flush（）；}为什么不重写Dispose方法（）？@jeevjyotsinghchabda是的，你可以。我通常习惯于使HttpContent类自包含。如果值对象在创建HttpContent对象之后但在写入网络之前发生更改，则有效负载将发生更改。但你的方法是100%有效的。我没有重载dispose，因为这个类没有分配非托管内存。

  var content = new JsonContent(new YourObject());
  var httpClient = new HttpClient();
  var response = httpClient.PostAsync("http://example.org/somewhere", content);

using System;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;
using Newtonsoft.Json;

namespace Http.Helper.Extensions
{
    public class JsonHttpContentSerializer : HttpContent
    {

        private object Value { get; set; }

        public JsonHttpContentSerializer(Object value)
        {
            this.Value = value;
        }


        protected override async Task SerializeToStreamAsync(Stream stream, TransportContext context)
        {
            using (var streamWriter = new StreamWriter(stream, new UTF8Encoding(false), 1024, true))
            {
                using (var jsonTextWriter = new JsonTextWriter(streamWriter) { Formatting = Formatting.None })
                {
                    var jsonSerializer = new JsonSerializer();
                    jsonSerializer.Serialize(jsonTextWriter, Value);
                    jsonTextWriter.Flush();
                }
            }

        }

        protected override bool TryComputeLength(out long length)
        {
            length = -1;
            return false;
        }

    }
}

var jsonSerializeContent = new JsonHttpContentSerializer(someContent);
httpRequestMessage.Content = jsonSerializeContent;