ASP.NET MVC Core 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'

ASP.NET Core 3.0 doesn't include JSON.NET which means you had to add the package explicitly before trying this code — Panagiotis Kanavos, Nov 29 '19 at 08:43

Andrei · Accepted Answer · 2022-03-18T16:01:45.443

193

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()));

edited Mar 18 '22 at 16:01

answered Nov 28 '19 at 21:03

Andrei

42,814
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26

If you have a Web API then instead of `.AddMvc()` you can also use `services.AddControllers().AddJsonOptions(...)`. – Tobias Feb 27 '20 at 15:26
26
as of asp.net core 3.1 and Microsoft.AspNetCore.Mvc.NewtonsoftJson 3.1.5, there is a slight change:
```
services.AddControllers()
.AddNewtonsoftJson(opts => opts.SerializerSettings.Converters.Add(new StringEnumConverter()));
```
– Sudhanshu Mishra Jul 12 '20 at 12:57
1

what if i dont want to do this accross the bard ? is there a way to do this as an attribute on my dto? – drowhunter Aug 23 '20 at 20:46
I found this website to be very helpful: https://www.jasongaylord.com/blog/2020/07/17/adding-newtonsoft-json-to-services – ashlar64 Aug 23 '20 at 21:39
8

@drowhunter If you want to just do this or a specific property, you can simply annotate the property in the return DTO like this `[JsonConverter(typeof(JsonStringEnumConverter))] public CategoryDto Category { get; set; }`. You will need to import the `using System.Text.Json.Serialization` namespace – Gavin Jun 09 '21 at 07:01
Thank you this worked for me `services.AddControllers()..AddJsonOptions(opts => { opts.JsonSerializerOptions.Converters.Add(new JsonStringEnumConverter()); })` – Qwerty Jun 17 '21 at 10:40

score 26 · Answer 2 · answered Sep 11 '20 at 03:16

some addition:
if use Newtonsoft.Json

Install-Package Microsoft.AspNetCore.Mvc.NewtonsoftJson

services
    .AddControllers()
    .AddNewtonsoftJson(options =>
        options.SerializerSettings.Converters.Add(new Newtonsoft.Json.Converters.StringEnumConverter()));

options.SerializerSettings.Converters

SerializerSettings is necessary

giorgi02 · Answer 3 · 2022-04-22T11:09:43.290

21

If you have a Minimal API this will be useful:

using System.Text.Json.Serialization;

builder.Services.Configure<Microsoft.AspNetCore.Http.Json.JsonOptions>(opt =>
{
    opt.SerializerOptions.Converters.Add(new JsonStringEnumConverter());
});

edited Apr 22 '22 at 11:09

answered Apr 22 '22 at 10:58

giorgi02

683
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score 9 · Answer 4 · answered Dec 24 '22 at 08:40

9

.NET 7.0 introduces this way:

builder.Services.ConfigureHttpJsonOptions(options => options.SerializerOptions.Converters.Add(new JsonStringEnumConverter()));

answered Dec 24 '22 at 08:40

asaf92

1,557
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score 1 · Answer 5 · edited Nov 18 '22 at 06:18

1

If you are using Aspnet Core MVC with the minimal API use this:

services.Configure<Microsoft.AspNetCore.Mvc.JsonOptions>(o => o.JsonSerializerOptions.Converters.Add(new JsonStringEnumConverter()));

edited Nov 18 '22 at 06:18

Backs

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answered May 26 '22 at 10:05

Michael Edwards

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ASP.NET MVC Core API Serialize Enums to String

5 Answers5

New System.Text.Json serialization

If you prefer Newtonsoft.Json

Linked