How to handle JSON data in POST request in C# (.NET Core 3.1)

Question

Previously (In .Net Core 2.1) I successfully handled JSON data with below method

[HttpPost]
[Route("sendJsonData")]
public JObject saveTemplate(JObject jsonString)
{

        string templateName = (string)jsonString.SelectToken("templateName");
        string filePathAndName = "D:\\" + "templates\\" + templateName + ".txt";

        using (StreamWriter file = File.CreateText(@filePathAndName))
        {
            JsonSerializer serializer = new JsonSerializer();
            serializer.Serialize(file, jsonString);
        }

    return jsonString;
}

But when I created the same method with .Net Core 3.1. It is not working showing some error with JObject. I am getting that JSON from below code

onSubmit() {
this.http.post("https://localhost:44350/ReportAPI/sendJsonData", this.surveyForm.value)
            .subscribe(
                data => console.log("success!", data),
                error => console.error("couldn't post because", error)
            );
}

Below is the error (Response from Postman)

{
    "type": "https://tools.ietf.org/html/rfc7231#section-6.5.1",
    "title": "One or more validation errors occurred.",
    "status": 400,
    "traceId": "|6e209814-4dd7396cc2dfa182.",
    "errors": {
        "$": [
            "The JSON value could not be converted to System.Collections.Generic.IEnumerable`1[Newtonsoft.Json.Linq.JToken]. Path: $ | LineNumber: 0 | BytePositionInLine: 14."
        ]
    }
}

JSON

{  
   "templateName":"BFS Survey",
   "surveyQuestions":[  
      {  
         "questionTitle":"Name",
         "questionType":"Text",
         "questionGroup":{  

         }
      },
      {  
         "questionTitle":"Age",
         "questionType":"Number",
         "questionGroup":{  

         }
      },
      {  
         "questionTitle":"Gender",
         "questionType":"Single choice",
         "questionGroup":{  
            "options":[  
               {  
                  "optionText":"Male"
               },
               {  
                  "optionText":"Female"
               },
               {  
                  "optionText":"Other"
               }
            ],
            "showRemarksBox":false
         }
      },
      {  
         "questionTitle":"Skills",
         "questionType":"Multi choice",
         "questionGroup":{  
            "options":[  
               {  
                  "optionText":"Java"
               },
               {  
                  "optionText":"Angular"
               },
               {  
                  "optionText":"Python"
               },
               {  
                  "optionText":"R"
               }
            ],
            "showRemarksBox":false
         }
      }
   ]
}

Code perfectly worked using .Net Core 2.1 but not working with 3.1. Please suggest me how resolve this issue.

I have so many questions about this implementation... can you show us the error? usually, a dedicated class is used to deserialize the json from the request body, instead of a plain JObject. Also, why are you catching an error just to throw it again? you could get rid of the entire try catch block, and it would act exactly the same — Glenn van Acker
– Glenn van Acker, Commented Dec 5, 2019 at 7:40
@RahulSharma It worked!!! Thanks a lot. Really appreciate it. :) — Abhi
– Abhi, Commented Dec 5, 2019 at 8:43

Rahul Sharma · Accepted Answer · 2019-12-05 08:46:09Z

17

In order to migrate from ASP.NET Core 2.x to 3.0, refer to this link:

Add a package reference to Microsoft.AspNetCore.Mvc.NewtonsoftJson
Add in Startup.cs, in method ConfigureServices: services.AddMvc().AddNewtonsoftJson();

answered Dec 5, 2019 at 8:46

Rahul Sharma

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