JsonOutputFormatter in ASP.NET Core 3.0

Question

In asp.net core 2.2 I used to have the following,

  var jsonSettings = new JsonSerializerSettings
  {
    ContractResolver = new SubstituteNullWithEmptyStringContractResolver()
  };

services.AddMvc(options =>
{
        options.OutputFormatters.RemoveType<JsonOutputFormatter>();
        options.OutputFormatters.Add(new ResponseJsonOutputFormatter(jsonSettings,ArrayPool<char>.Shared));
}

public class ResponseJsonOutputFormatter : JsonOutputFormatter
{
 // Stuff in here
}

However in 3.0 using:

services.AddControllersWithViews(options =>

and the type JsonOutputFormatter is no longer available.

What is the current suggested way of customizing a json response globally?

I tried using IOutputFormatter but it doesn't seem to be wired in when I set it within AddControllersWithViews as an OutputFormatters so not sure if there are extra steps?

Would middleware with the new endpoint routing be an option? Or is there a better way of achieving this?

Answer 1

To revert back to NewtonsoftJson and also configure its output formatter, first add a package reference to Microsoft.AspNetCore.Mvc.NewtonsoftJson and then in ConfigureServices you need to call Configure after calling AddController and AddNewtonsoftJson:

public void ConfigureServices(IServiceCollection services)
{
    services.AddControllers()
            .AddNewtonsoftJson();
    
    services.Configure<MvcOptions>(options =>
        {
            NewtonsoftJsonOutputFormatter jsonOutputFormatter = options.OutputFormatters.OfType<NewtonsoftJsonOutputFormatter>().Single();
        
            // makes changes to the Newtonsoft JSON Output Formatter here.
        });
}

Answer 2

I personally use Json.NET

• Simply add a package reference to Microsoft.AspNetCore.Mvc.NewtonsoftJson.
• Update Startup.ConfigureServices to call AddNewtonsoftJson.

services.AddMvc().AddNewtonsoftJson();

Json.NET settings can be set in the call to AddNewtonsoftJson:

services.AddMvc()
    .AddNewtonsoftJson(options =>
           options.SerializerSettings.ContractResolver =
              new CamelCasePropertyNamesContractResolver());

I am using the default options with compatibility mode

services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_3_0)
            .AddNewtonsoftJson(options => { options.SerializerSettings.ContractResolver =
             new DefaultContractResolver(); });

Reference Migrate from ASP.Net 2.2 to 3.0