Don't understand how to use JSON.NET with ASP.NET Core WebAPI - json

Question

I've completed my first ASP.NET Core Web API and I'd like to try my hand at manually serializing/deserializing JSON via the JSON.NET library. In the JSON.NET documentation they give the following simple manual serialization example:
public static string ToJson(this Person p)
{
StringWriter sw = new StringWriter();
JsonTextWriter writer = new JsonTextWriter(sw);
writer.WriteStartObject();
// "name" : "Jerry"
writer.WritePropertyName("name");
writer.WriteValue(p.Name);
// "likes": ["Comedy", "Superman"]
writer.WritePropertyName("likes");
writer.WriteStartArray();
foreach (string like in p.Likes)
{
writer.WriteValue(like);
}
writer.WriteEndArray();
writer.WriteEndObject();
return sw.ToString();
}
What's lacking for a beginner such as myself is how to use this string. For example, consider the following:
[HttpGet("/api/data")
[Produces("application/json")]
public IActionResult GetData()
{
return Ok(new Byte[SomeBigInt]);
}
In the above code I don't really know where ASP.NET Core serializes the array to JSON...I'm assuming it happens somewhere under the hood. If I were to manually serialize (using the JSON.NET example) some big Byte array, what do I do with the resultant string? Is it just "return Ok(myJsonString);"? Won't the built-in serializer - not knowing that it is already the result of a serialization operation- serialize it again?

Answer 1

Since Asp.Net Core is quite flexible, there are several ways to return JSON. If you want to return Json from a controller one of the most straight forward ways to do it is like this:
[HttpGet("/api/data")]
public JsonResult GetData() {
return Json(new {
fieldOneString = "some value",
fieldTwoInt= 2
});
}
Under the hood the Json() helper method on the Controlleris using JSON.NET to do the JSON serialization and then sending that as the response body.
You could do the same thing like this:
string jsonText = JsonConvert.SerializeObject(new {
fieldOneString = "some value",
fieldTwoInt= 2
});
Response.WriteAsync(jsonText);
Note: to use Response.WriteAsync(jsonText) you need to add using Microsoft.AspNetCore.Http to your file and have a project reference to Microsoft.AspNetCore.Http.Abstractions.