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
– Kirk Larkin, Commented Oct 15, 2019 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
– Alex Zaitsev, Commented Oct 15, 2019 at 10:10
Alright, so I guess you're using AddControllers in ConfigureServices, right? — Kirk Larkin
– Kirk Larkin, Commented Oct 15, 2019 at 10:10

Bart · Accepted Answer · 2021-10-12 14:21:55Z

113

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, 2021 at 14:21

Bart

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answered Oct 15, 2019 at 10:21

Kirk Larkin

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3 Comments

zion Over a year ago

Adding "options.JsonSerializerOptions.IgnoreNullValues = true;" had no effect

Rafał Praniuk Over a year ago

To others who hit this page looking for Enum conversion: [JsonConverter(typeof(JsonStringEnumConverter))] public enum SomeEnum

Nalin Jayasuriya Over a year ago

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);

tmaj · Accepted Answer · 2020-03-11 06:59:34Z

76

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, 2020 at 6:59

answered Oct 15, 2019 at 10:03

tmaj

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5 Comments

Alex Zaitsev Over a year ago

Hi, this sets settings on Json.NET level, how can it be done on ASP.NET level?

MrClan Over a year ago

It configures the settings on ASP.NET level, meaning default ModelBinding now happens using NewtonsoftJson serializer.

static_void Over a year ago

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.

jnt Over a year ago

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());  });

ThatBlairGuy Over a year ago

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.

OSP · Accepted Answer · 2019-12-08 16:05:50Z

48

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;
        });

answered Dec 8, 2019 at 16:05

OSP

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1 Comment

Arash Ghasemi Rad Over a year ago

Thank you @OSP, but what do you exactly mean "obviously not very good"?

Onur Dikmen · Accepted Answer · 2022-12-12 12:56:45Z

11

You can try System.Text.Json, the newly released Json nuget package converter. 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 12, 2022 at 12:56

answered Dec 14, 2020 at 0:09

Onur Dikmen

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6 Comments

Guru Stron Over a year ago

1. Not so newly 2.Can you please explain claim "Newtonsoft no longer works very well in .Net Core"? 3. what is "configirationSetting method" ?

Onur Dikmen Over a year ago

Hello @GuruStron, 1) it is newly, beacuse it is net core 3.1 libary supported. (devblogs.microsoft.com/dotnet/try-the-new-system-text-json-apis) 2) (learn.microsoft.com/en-us/dotnet/standard/serialization/… ) 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.

Guru Stron Over a year ago

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"" =)

Douglas Gaskell Over a year ago

Even in 2022 System.Text.Json is missing core flexibility features that make is a far from ideal candidate for JSON serialization. JSON is designed to be greedy in operation, System.Text.Json continually fails to match that requirement.

Murat Over a year ago

I also added "options.JsonSerializerOptions.NumberHandling = JsonNumberHandling.AllowReadingFromString;" for similar behavior to .NET framework.

|

Mohammad Komaei · Accepted Answer · 2022-05-08 04:30:38Z

5

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

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

edited May 8, 2022 at 4:30

answered Jan 26, 2022 at 14:30

Mohammad Komaei

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3 Comments

Serge Over a year ago

Question is about net 3.1

JustAMartin Over a year ago

My app has the old WebHost.CreateDefaultBuilder(args) left, which does not have .Services. How do I set the JsonOptions there?

Mohammad Komaei Over a year ago

Add it after AddControllers() methos in Startup.cs file.

Fahimeh Ahmadi · Accepted Answer · 2021-10-01 10:35:35Z

3

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;
           });
    }

answered Oct 1, 2021 at 10:35

Fahimeh Ahmadi

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