无法从POST请求反序列化HttpContent

Question

I am trying to send a POST request to a server.The request gets into the Middleware 's Invoke method.

However the Content is always null, no matter the type of the object.

Sender

public async Task<string> RunTestAsync(string request)
{
    try
    {
        var content = new StringContent(JsonConvert.SerializeObject(request),Encoding.UTF8,"application/json");

       var response=await this.client.PostAsync("http://localhost:8500/mat",
                              content);

        string str=await response.Content.ReadAsStringAsync();
        stringdata = JsonConvert.DeserializeObject<string>(str);
        return data;     
    }
    catch (Exception ex)
    {
        Console.WriteLine("Threw in client" + ex.Message);
        throw;
    }
}

Server

The server has no service defined ,just a plain middleware that responds on a route . ( The request gets in the Invoke method ! )

Startup

 public class Startup
   {
        public void ConfigureServices(IServiceCollection services) {

        }
        public void Configure(IApplicationBuilder app, IHostingEnvironment env) {

            app.UseDeveloperExceptionPage();
            app.UseBlazor<Client.Startup>();

            app.Map("/mid", a => {
                     a.UseMiddleware<Mware>();
                });
            });
        }
   }

Middleware

public class Mware
{
    public RequestDelegate next{get;set;}

    public Mware(RequestDelegate del)
    {
      this.next=del;
    }
    public async Task Invoke(HttpContext context)
    {

            using (var sr = new StreamReader(context.Request.Body))
            {
                string content = await sr.ReadToEndAsync();//null ,tried other types too , still null ,and the ContentLength is null too
                var request=JsonConvert.DeserializeObject<string>(content);
                if (request == null)
                {
                    return;
                }
            }
    }
}

I have checked my serialization and the object is serialized just fine.

Despite this I am always getting a null on the other side.

PS

I have also tried using no middleware just a plain delegate like below :

 public void Configure(IApplicationBuilder app, IHostingEnvironment env) {

        app.UseDeveloperExceptionPage();
        app.UseBlazor<Client.Startup>();

        app.Map("/mid",x=>{
            x.Use(async(context,del)=>{
                using (var sr = new StreamReader(context.Request.Body))
                {
                  string content = await sr.ReadToEndAsync();//null ,tried other types too , still null ,and the ContentLength is null too
                  var request=JsonConvert.DeserializeObject<string>(content);
                  if (request == null)
                  {
                    return;
                  }
                }
        });
    }

Even without a dedicated middleware the problem persists.

The problem is not the middleware , its the request that is serialized correctly in the client, sent to the server ,and somehow its body shows up as null .

I would've understood if it failed to deserialize the object , but the HttpContext.Request.Body as a string is received null and its length is null !!

Answer 1

In your example, the client code calls the route "/mat", but the middleware is configured at "/mid". If the code you're running has the same error, the middleware won't get hit, and you'll always get an empty response that, from the client, looks the same as if the middleware received null . Make sure you're also using the right port number--mine was :5000 , but it can vary depending on the runtime configuration.

Are you testing with a debugger and breakpoints? If not, I highly recommend trying. I was able to find that error pretty quickly because I set a breakpoint in the server-side code, and observed that it wasn't getting hit. If a debugger isn't an option, consider "failing loudly" by throwing an exception (instead of simply returning) to make it more obvious whether or not you're actually hitting the condition you think you're hitting.

Answer 2

Not sure what's exactly wrong with your code, but this works:

public class Startup
{
  // This method gets called by the runtime. Use this method to add services to the container.
  // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
  public void ConfigureServices(IServiceCollection services)
  {
  }

  // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
  public void Configure(IApplicationBuilder app, IHostingEnvironment env)
  {
    if (env.IsDevelopment())
    {
      app.UseDeveloperExceptionPage();
    }

    app.Run(async (context) =>
    {
      var request = context.Request;
      var body = request.Body;

      request.EnableRewind();
      var buffer = new byte[Convert.ToInt32(request.ContentLength)];
      await request.Body.ReadAsync(buffer, 0, buffer.Length);
      var bodyAsText = Encoding.UTF8.GetString(buffer);
      request.Body = body;
      await context.Response.WriteAsync(bodyAsText);
    });
  }
}

Running this in chrome dev tools:

fetch('http://localhost:39538', {
  method: 'POST',
  body: JSON.stringify({
    title: 'foo',
    body: 'bar',
    userId: 1
  }),
  headers: {
    'Content-type': 'application/json; charset=UTF-8'
  }
})
.then(res => res.json())
.then(console.log)

Yields the following in the browser:

{"title":"foo","body":"bar","userId":1}

Answer 3

suppose your request is request= @" {"title":"foo","body":"bar","userId":1}";

call RunTestAsync(request); run just this JsonConvert.SerializeObject(request); I'm sure it fails because its not serializable. and if it is it should be
some object of serializable class

(Serializableclass request)

try this var content = new StringContent(request, Encoding.UTF8, "application/json");

public async Task RunTestAsync(string request) { try { var content = new StringContent(JsonConvert.SerializeObject(request),Encoding.UTF8,"application/json");

   var response=await this.client.PostAsync("http://localhost:8500/mat",
                          content);

    string str=await response.Content.ReadAsStringAsync();
    stringdata = JsonConvert.DeserializeObject<string>(str);
    return data;     
}
catch (Exception ex)
{
    Console.WriteLine("Threw in client" + ex.Message);
    throw;
}

}