How to set json serializer settings in asp.net core 3?

Question

json serializer settings for legacy asp.net core applications were set by adding AddMvc().AddJsonOptions(), but I don't use AddMvc() in asp.net core 3. So how can I set global json serialization settings?

If you don't use `AddMvc`, what _do_ you use? Are you using e.g. `AddControllers` or are you just not using MVC at all? — Kirk Larkin, Oct 15 '19 at 10:09
@KirkLarkin i use default way of building asp.net core 3 app - `app.UseEndpoints(endpoints => { endpoints.MapControllers() })` and `services.AddControllers();` — Alex Zaitsev, Oct 15 '19 at 10:10
Alright, so I guess you're using `AddControllers` in `ConfigureServices`, right? — Kirk Larkin, Oct 15 '19 at 10:10

score 90 · Accepted Answer · edited Oct 12 '21 at 14:21

90

AddMvc returns an IMvcBuilder implementation, which has a corresponding AddJsonOptions extension method. The new-style methods AddControllers, AddControllersWithViews, and AddRazorPages also return an IMvcBuilder implementation. Chain with these in the same way you would chain with AddMvc:

services.AddControllers()
    .AddJsonOptions(options =>
    {
        // ...
    });

Note that options here is no longer for Json.NET, but for the newer System.Text.Json APIs. If you still want to use Json.NET, see tymtam's answer

edited Oct 12 '21 at 14:21

Bart

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answered Oct 15 '19 at 10:21

Kirk Larkin

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Adding "options.JsonSerializerOptions.IgnoreNullValues = true;" had no effect – zion Jan 17 '20 at 14:14
8

To others who hit this page looking for Enum conversion: [JsonConverter(typeof(JsonStringEnumConverter))] public enum SomeEnum – Rafał Praniuk Apr 07 '20 at 15:09
For ASP.NET Core 3.1 (May/2021), we can specify the following to ask the JSON serializer not not serialize null values via the startup.cs file: services.AddControllers() .AddJsonOptions(options => options.JsonSerializerOptions.IgnoreNullValues = true); – Nalin Jayasuriya May 30 '21 at 10:47

tymtam · Answer 2 · 2020-03-11T06:59:34.703

71

Option A. AddControllers

This is still MVC, and requires Microsoft.AspNetCore.Mvc.NewtonsoftJson nuget package, but you said you use AddControllers.

From Add Newtonsoft.Json-based JSON format support

services.AddControllers().AddNewtonsoftJson(options =>
{
    // Use the default property (Pascal) casing
    options.SerializerSettings.ContractResolver = new DefaultContractResolver();

    // Configure a custom converter
    options.SerializerOptions.Converters.Add(new MyCustomJsonConverter());
});

Option B. DefaultSettings

JsonConvert.DefaultSettings = () => new JsonSerializerSettings (...)

JsonConvert.DefaultSettings Property

Gets or sets a function that creates default JsonSerializerSettings. Default settings are automatically used by serialization methods on JsonConvert, and ToObject () and FromObject(Object) on JToken. To serialize without using any default settings create a JsonSerializer with Create().

edited Mar 11 '20 at 06:59

answered Oct 15 '19 at 10:03

tymtam

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Hi, this sets settings on Json.NET level, how can it be done on ASP.NET level? – Alex Zaitsev Oct 15 '19 at 10:06
2

It configures the settings on ASP.NET level, meaning default ModelBinding now happens using NewtonsoftJson serializer. – MrClan Mar 11 '20 at 05:55
Thank you, Option A worked for me. Upgraded from 2.2 to 3.1 and my endpoint broke because `System.Text.Json` doesn't handle polymorphism or enums properly. Nice easy way to change the default serializer. – static_void Apr 14 '20 at 14:11
1

Example for ignroing null values and converting enums to strings: `services.AddControllersWithViews().AddNewtonsoftJson(o => { o.SerializerSettings.NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore; o.SerializerSettings.Converters.Add(new Newtonsoft.Json.Converters.StringEnumConverter()); });` – jnt Sep 18 '20 at 12:50
Not sure I'd do this on a new project, but moving legacy code to a new version... +1 for the `AddNewtonsoftJson()` and the link to the docs. – ThatBlairGuy Jul 16 '21 at 18:05

score 41 · Answer 3 · answered Dec 08 '19 at 16:05

Adding Newtonsoft is not necessary, quite a problems with adding Newtonsoft compatibility packages on .Net Core 3.0 project.

See also https://github.com/aspnet/AspNetCore/issues/13564

Of course, one would celebrate property naming PascalCase, NA at the moment... So null for PropertyNamingPolicy means PascalCase, which is obviously not very good.

// Pascal casing
services.AddControllersWithViews().
        AddJsonOptions(options =>
        {
            options.JsonSerializerOptions.PropertyNameCaseInsensitive = true;
            options.JsonSerializerOptions.PropertyNamingPolicy = null;
        });

Thank you @OSP, but what do you exactly mean "obviously not very good"? — Arash Ghasemi Rad, Jan 31 '21 at 06:17

score 8 · Answer 4 · edited Dec 14 '20 at 00:16

8

You can try System.Text.Json, the newly released Json nuget package converter. Newtonsoft no longer works very well in .Net Core. Startup.cs as below You can write this code inside the configirationSetting method.

 services.AddControllers()
     .AddJsonOptions(options =>
      {
          options.JsonSerializerOptions.PropertyNameCaseInsensitive = true;
          options.JsonSerializerOptions.PropertyNamingPolicy = null;
          options.JsonSerializerOptions.Converters.Add (new JsonStringEnumConverter ());
      });

edited Dec 14 '20 at 00:16

Guru Stron

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answered Dec 14 '20 at 00:09

Onur Dikmen

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1. Not so newly 2.Can you please explain claim _"Newtonsoft no longer works very well in .Net Core"_? 3. what is _"configirationSetting method"_ ? – Guru Stron Dec 14 '20 at 00:17
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Hello @GuruStron, 1) it is newly, beacuse it is **net core 3.1** libary supported. (https://devblogs.microsoft.com/dotnet/try-the-new-system-text-json-apis/) 2) (https://docs.microsoft.com/en-us/dotnet/standard/serialization/system-text-json-migrate-from-newtonsoft-how-to?pivots=dotnet-5-0 ) 3) Microsoft is now using new nuget packages from its own freamwork in all software. For this reason, it withdraws support from many of them and directs them to their own packages. **Newtonsoft.Json** provides support, but now **Microsoft** wants its own package for Core. – Onur Dikmen Dec 24 '20 at 06:29
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1) Article you've linked in this point is around 1.5 years old 2) this one is about HOW to migrate and does not explain claim in question =)) 3) this point does not answer question _"what is "configirationSetting method""_ =) – Guru Stron Dec 25 '20 at 16:17

M Komaei · Answer 5 · 2022-05-08T04:30:38.947

4

In .net6 add this code after .AddControllers() in program.cs file:

builder.Services.AddControllers().AddJsonOptions(options =>
{
    options.JsonSerializerOptions.PropertyNamingPolicy = null;
});

edited May 08 '22 at 04:30

answered Jan 26 '22 at 14:30

M Komaei

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Question is about net 3.1 – Serge Jan 26 '22 at 14:35

score 1 · Answer 6 · answered Oct 01 '21 at 10:35

1.install NuGet : Microsoft.AspNetCore.Mvc.NewtonsoftJson or

   <ItemGroup>
        <PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" Version="3.1.2" />
    </ItemGroup>

2. Add Startup.cs :

   public void ConfigureServices(IServiceCollection services)
     {
         //JSON Serializer
         services.AddControllers().AddNewtonsoftJson(options =>
           {
            options.SerializerSettings.ReferenceLoopHandling = 
               Newtonsoft.Json.ReferenceLoopHandling.Ignore;
           });
    }

How to set json serializer settings in asp.net core 3?

6 Answers6

Option A. AddControllers

Option B. DefaultSettings

Linked