Serialize Enum as String for Requests and Responses in ASP.NET Core

Configure a global converter

builder.Services.AddControllers()
  .AddJsonOptions(options =>
  {
      options.JsonSerializerOptions.Converters.Add(new JsonStringEnumConverter());
  });

Or you could just annotate the property with this attribute if you don't want it applied to all properties in your app

public class User
{
  ...
  [JsonConverter(typeof(JsonStringEnumConverter))]
  public Gender Gender { get; set; }
  ...
}

This will return enums as their string representations. It will also accept strings and map them to the enum if they match exactly (case insensitive (I think? I'm not sure))