asp.net core API中post提交，得到的结果为什么是这样？

[一品梅]

namespace WebApplication1.Controllers
{
    [Route("ActionApi/[controller]")]
    [ApiController]

    public class UserInfoController : ControllerBase
    {
        //检查用户名是否已注册
        private ApiTools tool = new ApiTools();
        [Route("CheckUserName")]
        [HttpPost("{username}")]
        //[HttpPost]
        public HttpResponseMessage CheckUserName(string _userName)
        {
            int num = UserInfoGetCount(_userName);//查询是否存在该用户
            if (num > 0)
            {
                return tool.MsgFormat(ResponseCode.操作失败, "不可注册/用户已注册", "1 " + _userName);
            }
            else
            {
                return tool.MsgFormat(ResponseCode.成功, "可注册", "0 " + _userName);
            }
        }

        private int UserInfoGetCount(string username)
        {
            //return Convert.ToInt32(SearchValue("select count(id) from userinfo where username='" + username + "'"));
            return username == "admin" ? 1 : 0;
        }
    }
}

 public class ApiTools
    {
        private string msgModel = "{{\"code\":{0},\"message\":\"{1}\",\"result\":{2}}}";
        public ApiTools()
        {
        }
        public HttpResponseMessage MsgFormat(ResponseCode code, string explanation, string result)
        {
            string r = @"^(\-|\+)?\d+(\.\d+)?$";
            string json = string.Empty;
            if (Regex.IsMatch(result, r) || result.ToLower() == "true" || result.ToLower() == "false" || result == "[]" || result.Contains('{'))
            {
                json = string.Format(msgModel, (int)code, explanation, result);
            }
            else
            {
                if (result.Contains('"'))
                {
                    json = string.Format(msgModel, (int)code, explanation, result);
                }
                else
                {
                    json = string.Format(msgModel, (int)code, explanation, "\"" + result + "\"");
                }
            }
            return new HttpResponseMessage { Content = new StringContent(json, System.Text.Encoding.UTF8, "application/json") };
        }
    }

我用postman选择POST，输入网址及入参：
http://localhost:49449/ActionApi/UserInfo/CheckUserName?username=ZHANGSAN
结果得到的结果是这个,真是太奇怪了。
{
"version": {
"major": 1,
"minor": 1,
"build": -1,
"revision": -1,
"majorRevision": -1,
"minorRevision": -1
},
"content": {
"headers": [
{
"key": "Content-Type",
"value": [
"application/json; charset=utf-8"
]
}
]
},
"statusCode": 200,
"reasonPhrase": "OK",
"headers": [],
"requestMessage": null,
"isSuccessStatusCode": true
}

[一品梅]

return new HttpResponseMessage { Content = new StringContent(json, System.Text.Encoding.UTF8, "application/json") } 我转到定义看了下 public class HttpResponseMessage : IDisposable { public HttpResponseMessage(); public HttpResponseMessage(HttpStatusCode statusCode); public Version Version { get; set; } public HttpContent Content { get; set; } public HttpStatusCode StatusCode { get; set; } public string ReasonPhrase { get; set; } public HttpResponseHeaders Headers { get; } public HttpRequestMessage RequestMessage { get; set; } public bool IsSuccessStatusCode { get; } public void Dispose(); public HttpResponseMessage EnsureSuccessStatusCode(); public override string ToString(); protected virtual void Dispose(bool disposing); } 不知内容为什么没有加载上去，难道新版本HttpResponseMessage的定义变了。 我是拿网上的这个链接来学习的。不知人家的为什么可以调试出那个结果。源代码和结果链接如下， 兄弟们可以调试一下看看，找到原因的请留个言，十分感谢。 (9条消息)C# 搭建一个简单的WebApi项目_lwpoor123的博客-CSDN博客 https://blog.csdn.net/lwpoor123/article/details/78285148

[一品梅]

再深入看了下，翻到HttpContent的定义，为什么HttpContent只显示一个头文件？

public abstract class HttpContent : IDisposable
    {
        protected HttpContent();

        public HttpContentHeaders Headers { get; }

        public Task CopyToAsync(Stream stream, TransportContext context);
        public Task CopyToAsync(Stream stream);
        public void Dispose();
        public Task LoadIntoBufferAsync();
        public Task LoadIntoBufferAsync(long maxBufferSize);
        public Task<byte[]> ReadAsByteArrayAsync();
        public Task<Stream> ReadAsStreamAsync();
        public Task<string> ReadAsStringAsync();
        protected virtual Task<Stream> CreateContentReadStreamAsync();
        protected virtual void Dispose(bool disposing);
        protected abstract Task SerializeToStreamAsync(Stream stream, TransportContext context);
        protected internal abstract bool TryComputeLength(out long length);
    }

public abstract class HttpContent : IDisposable { protected HttpContent(); public HttpContentHeaders Headers { get; }//怎么只要这一个属性？？？ public Task CopyToAsync(Stream stream, TransportContext context); public Task CopyToAsync(Stream stream); public void Dispose(); public Task LoadIntoBufferAsync(); public Task LoadIntoBufferAsync(long maxBufferSize); public Task<byte[]> ReadAsByteArrayAsync(); public Task<Stream> ReadAsStreamAsync(); public Task<string> ReadAsStringAsync(); protected virtual Task<Stream> CreateContentReadStreamAsync(); protected virtual void Dispose(bool disposing); protected abstract Task SerializeToStreamAsync(Stream stream, TransportContext context); protected internal abstract bool TryComputeLength(out long length);

[欧皇神降术]

HttpResponseMessage.Content.ReadAsStringAsync().Result

[正怒月神]

一直没有注意，然后我打开.net mvc和.net core mvc测试了一下各自的webapi。 的确楼主发现的问题是对的。 .net mvc webapi .net mvc core webapi 顺便搜了一下。 有人提供了解决方案 但是我没测试。 https://www.cnblogs.com/dudu/p/6872657.html

[八爻老骥]

就是说HttpContent是异步加载的，而你想要得到的是同步结果，所以不能用或不能直接用HttpContent来返回结果，要么直接返回一个可序列化对象，要么如3楼所写的那样。

[一品梅]

谢谢各位交流很有裨益。

[江湖评谈]

Mark ，不错的解决方案

[SayoKun]

引用 4 楼 正怒月神 的回复:

一直没有注意，然后我打开.net mvc和.net core mvc测试了一下各自的webapi。 的确楼主发现的问题是对的。 .net mvc webapi .net mvc core webapi 顺便搜了一下。 有人提供了解决方案 但是我没测试。 https://www.cnblogs.com/dudu/p/6872657.html

这个解决方案中的2楼提出了另一个解决方案，就是直接返回 Task<ContentResult>。这个我也没测，不过应该可以~