Error with OkObjectResult and json string when moving from a FunctionApp to ASP.NET Core WebAPI

Question

I had a function app in C# that made a function call to a stored procedure and returned the results as follows:

 connection.Open();
 SqlDataReader reader = command.ExecuteReader();
 var dataTable = new DataTable();
 dataTable.Load(reader);
 jsonstring = JsonConvert.SerializeObject(dataTable);                  
 connection.Close();
    
 return new OkObjectResult(jsonstring); 

When I moved this code to >NET CORE I get the following error message: CS0029: Cannot implicitly convert type Microsoftaspnetcore.mvc.OkObjectResult to Microsoftaspnetcore.mvc.JsonResult

But if I switch to JsonResult(jsonstring) then my application thows this error: Error parsing JSON data: SyntaxError: Unexpected end of JSON when I run JSON.parse(data)

I have tried different formats but that did not help.

Answer 1

With JsonResult(jsonstring), you are returning the response with JSON array string as below:

"[/* JSON objects */]"

Instead of returning JSON in string, you should return the array as:

using Newtonsoft.Json.Linq;

public JsonResult YourApiAction(/* arguments */)
{
    ...

    return new JsonResult(JArray.FromObject(dataTable));
}

Or you can return the dataTable directly. It will be serialized as a JSON array.

public JsonResult YourApiAction(/* arguments */)
{
    ...

    return new JsonResult(dt);
}

Side note, if your Controller class inherits Controller as the base class, you can use the Json method.

public class YourController : Controller
{
    public JsonResult YourApiAction(/* arguments */)
    {
        ...

        return Json(dt);
    }
}