Add IMvcCoreBuilder.AddJsonOptions extension method

Fixes #4967

src/Microsoft.AspNetCore.Mvc.Formatters.Json/DependencyInjection/MvcJsonMvcCoreBuilderExtensions.cs

@@ -47,6 +47,30 @@ namespace Microsoft.Extensions.DependencyInjection
             return builder;
         }
 
+        /// <summary>
+        /// Adds configuration of <see cref="MvcJsonOptions"/> for the application.
+        /// </summary>
+        /// <param name="builder">The <see cref="IMvcCoreBuilder"/>.</param>
+        /// <param name="setupAction">The <see cref="MvcJsonOptions"/> which need to be configured.</param>
+        /// <returns>The <see cref="IMvcCoreBuilder"/>.</returns>
+        public static IMvcCoreBuilder AddJsonOptions(
+           this IMvcCoreBuilder builder,
+           Action<MvcJsonOptions> setupAction)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            if (setupAction == null)
+            {
+                throw new ArgumentNullException(nameof(setupAction));
+            }
+
+            builder.Services.Configure<MvcJsonOptions>(setupAction);
+            return builder;
+        }
+
         // Internal for testing.
         internal static void AddJsonFormatterServices(IServiceCollection services)
         {

test/Microsoft.AspNetCore.Mvc.Test/MvcServiceCollectionExtensionsTest.cs

@@ -30,6 +30,8 @@ using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.DependencyInjection.Extensions;
 using Microsoft.Extensions.Options;
 using Moq;
+using Newtonsoft.Json.Serialization;
+using Newtonsoft.Json;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Mvc
@@ -226,6 +228,23 @@ namespace Microsoft.AspNetCore.Mvc
             Assert.Same(manager, descriptor.ImplementationInstance);
         }
 
+        [Fact]
+        public void AddMvcCore_AddsMvcJsonOption()
+        {
+            // Arrange
+            var services = new ServiceCollection();
+
+            // Act
+            services.AddMvcCore()
+                .AddJsonOptions((options) =>
+                {
+                    options.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();
+                });
+
+            // Assert
+            Assert.Single(services, d => d.ServiceType == typeof(IConfigureOptions<MvcJsonOptions>));
+        }
+
         private IEnumerable<Type> SingleRegistrationServiceTypes
         {
             get