.NET Core: Remove null fields from API JSON response

Question

On a global level in .NET Core 1.0 (all API responses), how can I configure Startup.cs so that null fields are removed/ignored in JSON responses?

Using Newtonsoft.Json, you can apply the following attribute to a property, but I'd like to avoid having to add it to every single one:

[JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
public string FieldName { get; set; }
[JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
public string OtherName { get; set; }

Answer 1

.NET Core 1.0

In Startup.cs, you can attach JsonOptions to the service collection and set various configurations, including removing null values, there:

public void ConfigureServices(IServiceCollection services)
{
     services.AddMvc()
             .AddJsonOptions(options => {       
                  options.SerializerSettings
                         .NullValueHandling = NullValueHandling.Ignore;
     });
}

.NET Core 3.1

Instead of this line:

options.SerializerSettings.NullValueHandling = NullValueHandling.Ignore;

Use:

options.JsonSerializerOptions.IgnoreNullValues = true;

.NET 5.0

Instead of both variants above, use:

 options.JsonSerializerOptions.DefaultIgnoreCondition 
                       = JsonIgnoreCondition.WhenWritingNull;

The variant from .NET Core 3.1 still works, but it is marked as NonBrowsable (so you never get the IntelliSense hint about this parameter), so it is very likely that it is going to be obsoleted at some point.

Answer 2

This can also be done per controller in case you don't want to modify the global behavior:

public IActionResult GetSomething()
{
   var myObject = GetMyObject();
   return new JsonResult(myObject, new JsonSerializerSettings() 
   { 
       NullValueHandling = NullValueHandling.Ignore 
   });
};

Answer 3

I found that for dotnet core 3 this solves it -

services.AddControllers().AddJsonOptions(options => {
     options.JsonSerializerOptions.IgnoreNullValues = true;
});

Answer 4

In net 5, it's actually DefaultIgnoreCondition:

public void ConfigureServices(IServiceCollection services)
{
   services.AddControllers()
           .AddJsonOptions(options =>
                {
 options.JsonSerializerOptions.DefaultIgnoreCondition =
        System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull;
                });
        }

This will prevent both serializazion and deserialization of any null value without needing any extra attribute on properties.

Answer 5

.Net core 6 with Minimal API:

using Microsoft.AspNetCore.Http.Json;

builder.Services.Configure<JsonOptions>(options => 
         options.SerializerOptions.DefaultIgnoreCondition 
   = JsonIgnoreCondition.WhenWritingDefault | JsonIgnoreCondition.WhenWritingNull);

Answer 6

In .Net 5 and greater, if you are using AddNewtonsoftJson instead of AddJsonOptions, the setting is as following

 services.AddMvc(options =>
     {
        //any other settings
     })
     .AddNewtonsoftJson(options =
     {
        options.SerializerSettings.NullValueHandling = NullValueHandling.Ignore;
     });

Answer 7

If you would like to apply this for specific properties and only use System.Text.Json then you can decorate properties like this

[JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
public string Market { get; set; }

Answer 8

The following works for .NET Core 3.0, in Startup.cs > ConfigureServices():

services.AddMvc()
    .AddJsonOptions(options =>
    {
        options.JsonSerializerOptions.IgnoreNullValues = true;
    });

Answer 9

In Asp.Net Core you can also do it in the action method, by returning

return new JsonResult(result, new JsonSerializerOptions
{
   IgnoreNullValues = true,
});

Answer 10

Lots of answers, and I've actually used one or two of them in the past but, currently, in DOTNET 7+ (probably 6 too) it is as simple as the Minimal API Tutorial's section Configure JSON Serialization Options shows. Just use Builder.Services.ConfigureHttpJsonOptions() as per the excerpt below:

var builder = WebApplication.CreateBuilder(args);

builder.Services.ConfigureHttpJsonOptions(options => {
    options.SerializerOptions.DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull;
    // set other desired options here...
    options.SerializerOptions.WriteIndented = true;
    options.SerializerOptions.IncludeFields = true;
});

var app = builder.Build();

Now you can also easily (see the tutorial for more information) add options per endpoint as bellow:

// creates a JsonSerializerOptions object with default "Web" options
var options = new JsonSerializerOptions(JsonSerializerDefaults.Web)
    { WriteIndented = true };

// pass it to the endpoint mapping 
app.MapGet("/", () => 
    Results.Json(new Todo { Name = "Walk dog", IsComplete = false }, options));

Answer 11

I used the below in my .net core v3.1 MVC api.

 services.AddMvc().AddJsonOptions(options =>
            {

                options.JsonSerializerOptions.DefaultIgnoreCondition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull;
            });

Answer 12

One more way in .Net 6, for specific ObjectResult:

public class IdentityErrorResult : BadRequestObjectResult
{
    public IdentityErrorResult([ActionResultObjectValue] object? error) : base(error)
    {
        Formatters.Add(new SystemTextJsonOutputFormatter(new JsonSerializerOptions
        {
            DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull
        }));
    }
}

in Controller:

public IdentityErrorResult IdentityError(ErrorResponseObject value)
  => new IdentityErrorResult(value);

Answer 13

If you are using .NET 6 and want to get rid of the null values in your REST response, on Program.cs just add the following lines:

builder.Services.AddControllers()
    .AddJsonOptions(options =>
    {
        options.JsonSerializerOptions.DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull;
    });

Answer 14

For .NET 8

 builder.Services.AddControllers()
                .AddJsonOptions(o => o.JsonSerializerOptions.DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingDefault | JsonIgnoreCondition.WhenWritingNull);

Answer 15

The code below work for me in .Net core 2.2

services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);