.NET Core: Remove null fields from API JSON response

.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.

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