Web API：FromBody 始终为空

Question

I'm trying to develop a web API, and when I test the POST method, the body is always null. I have tried everything when sending the request:

HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://localhost:1748/api/SomeAPI");
req.Method = "post";;

var aaa = Encoding.Default.GetBytes("Test");
req.ContentType = "application/xml";
req.ContentLength = aaa.Length;
req.GetRequestStream().Write(aaa, 0, aaa.Length);

HttpWebResponse res = (HttpWebResponse)req.GetResponse();
using (System.IO.StreamReader sr = new System.IO.StreamReader(res.GetResponseStream())) {
    Console.WriteLine(sr.ReadToEnd());
}

I use a breakpoint, and the API is called properly, but the body member is always null:

[HttpPost]
public void Post([FromBody]String test) {

}

Answer 1

Your Content Type is set to XML so you must pass the data as XML. This means wrapping your data in <string> element.

I would recommend using RestSharp ( http://restsharp.org/ ) for making WebAPI calls from .Net.

        var client = new RestClient("http://localhost:1748/");
        var request = new RestRequest("api/SomeAPI", Method.POST);
        request.AddBody("Test");
        var response = client.Execute(request);

Update

I have created a sample project and it works absolutely fine:

Server side:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Http;

namespace WebApplication1.Controllers
{
    public class HomeController : ApiController
    {
        [Route("api/TestAPI")]
        [HttpPost]
        public IHttpActionResult Post([FromBody]String test)
        {
            return Ok(string.Format("You passed {0}.", test));
        }
    }
}

Client side:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://localhost:1748/api/TestAPI");
            req.Method = "post"; ;
            var aaa = Encoding.Default.GetBytes("\"Test\"");
            req.ContentType = "application/json";
            req.ContentLength = aaa.Length;
            req.GetRequestStream().Write(aaa, 0, aaa.Length);
            HttpWebResponse res = (HttpWebResponse)req.GetResponse();
            using (System.IO.StreamReader sr = new System.IO.StreamReader(res.GetResponseStream()))
            {
                Console.WriteLine(sr.ReadToEnd());
            }
        }
    }
}

After installing the WEB API service in IIS and running the console app it prints:

"You passed Test."

Please note the quotes around the response. If you want to use XML then you need to modify the content type and data you are sending:

var aaa = Encoding.Default.GetBytes("<string xmlns=\"http://schemas.microsoft.com/2003/10/Serialization/\">Test</string>");

The response you will get is

<string xmlns="http://schemas.microsoft.com/2003/10/Serialization/">You passed Test.</string>

Both samples in the debugger will have correct value passed in the test parameter.

Answer 2

try

[HttpPost]
public void SomeApi()
{
   var test = HttpContext.Current.Request.Form["Test"];
}

If u send correctly the value,this will work 100%

Answer 3

Two things to try, 1st, try your request using a tried and tested tool like Postman. This will eliminate any chance your request is malformed in any way. 2nd, try changing your ContentType to text/plain. It's possible the request pipeline is seeing application/xml but your request body is invalid xml which really should be a bad request but is just being serialized as null.