ASP.NET MVC Core 3.0 API Serialize Enums to String

Question

How to serialize Enum fields to String instead of an Int in ASP.NET MVC Core 3.0? I'm not able to do it the old way.

services.AddMvc().AddJsonOptions(opts =>
{
    opts.JsonSerializerOptions.Converters.Add(new StringEnumConverter());
})

I'm getting an error:

cannot convert from 'Newtonsoft.Json.Converters.StringEnumConverter' to 'System.Text.Json.Serialization.JsonConverter'

Answer 1

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 =>
    {
        opts.JsonSerializerOptions.Converters.Add(new JsonStringEnumConverter());
    })

More info here. The documentation can be found here.

If you prefer Newtonsoft.Json

You can also use "traditional" Newtonsoft.Json serialization:

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