ASP.NET MVC Core API Serialize Enums to String

New System.Text.Json serialization

ASP.NET MVC Core 3.0 uses built-in JSON serialization. Use System.Text.Json.Serialization.JsonStringEnumConverter (with “Json” prefix):

services
    .AddMvc()
    // Or .AddControllers(...)
    .AddJsonOptions(opts =>
    {
        var enumConverter = new JsonStringEnumConverter();
        opts.JsonSerializerOptions.Converters.Add(enumConverter);
    })

More info here. The documentation can be found here.

If you prefer Newtonsoft.Json

You can also use “traditional” Newtonsoft.Json serialization:

Install-Package Microsoft.AspNetCore.Mvc.NewtonsoftJson

And then:

services
    .AddControllers()
    .AddNewtonsoftJson(opts => opts
        .Converters.Add(new StringEnumConverter()));