Dynamically creating a JSON object in C# based on provided values

November 18, 2021

I am trying to dynamically create a JSON object based on the values provided to me.

1st Scenario – I have all the values

 string param1 = "Hey";
 string param2 = "Bye";
 string param3 = "Later";

I would derive my Json like so:

 private string BuildJson (string param1, string param2, string param3)
 {
       //Passed values for example
      //param1 = "Hey";
      //param2 = "Bye";
      //param3 = "Later";

      object jJson = new 
      {
          VALS= new 
             {
                 val1 = param1,
                 val2 = param2,
                 val3 = param3
             }
      };

      return JsonConvert.SerializeObject(jJson );
 }

And this works great. However, now I’m trying to find a way to create this same JSON object, without knowing which param will have values. If there is no value, then I don’t want my jJson to have that property.

So for example

  private string BuildJson (string param1, string param2, string param3)
  {
   //Passed values for example
  //param1 = "Hey";
  //param2 = null;
  //param3 = "Later";

  //Since param2 is NULL, I would NOT want to have it all together in my JSON like below

  object jJson = new 
  {
      VALS= new 
         {
             val1 = param1,
             val3 = param3
         }
  };

  return JsonConvert.SerializeObject(jJson );
}

Is there an alternative way to dynamically create JSON like this? Thanks.

>Solution :

Since this is Newtonsoft, just include NullValueHandling = NullValueHandling.Ignore

Given

private static string BuildJson(string param1, string param2, string param3)
{

   object jJson = new
   {
      VALS = new
      {
         val1 = param1,
         val2 = param2,
         val3 = param3
      }
   };

   return JsonConvert.SerializeObject(jJson, 
      Formatting.Indented,
      new JsonSerializerSettings()
      {
         NullValueHandling = NullValueHandling.Ignore
      });
}

Usage

var result = BuildJson("asd", null, "sdf");
Console.WriteLine(result);

Output

{
  "VALS": {
    "val1": "asd",
    "val3": "sdf"
  }
}

_{Disclaimer : I would recommend Text.Json for any greenfield development, and would also dissuade you from using anonymous types like this and instead use actual concrete models.}