Add UnprocessableEntityResult, UnprocessableEntityObjectResult and ControllerBase.UnprocessableEntity methods (#6851)

* Added UnprocessableEntityResult

* Added UnprocessableEntityObjectResult

* Added UnprocessableEntity overloads to ControllerBase

Fixes https://github.com/aspnet/Mvc/issues/6795

src/Microsoft.AspNetCore.Mvc.Core/ControllerBase.cs

@@ -1400,6 +1400,7 @@ namespace Microsoft.AspNetCore.Mvc
         /// <summary>
         /// Creates an <see cref="BadRequestObjectResult"/> that produces a <see cref="StatusCodes.Status400BadRequest"/> response.
         /// </summary>
+        /// <param name="error">An error object to be returned to the client.</param>
         /// <returns>The created <see cref="BadRequestObjectResult"/> for the response.</returns>
         [NonAction]
         public virtual BadRequestObjectResult BadRequest(object error)
@@ -1408,6 +1409,7 @@ namespace Microsoft.AspNetCore.Mvc
         /// <summary>
         /// Creates an <see cref="BadRequestObjectResult"/> that produces a <see cref="StatusCodes.Status400BadRequest"/> response.
         /// </summary>
+        /// <param name="modelState">The model state dictionary containing errors to be returned to the client.</param>
         /// <returns>The created <see cref="BadRequestObjectResult"/> for the response.</returns>
         [NonAction]
         public virtual BadRequestObjectResult BadRequest(ModelStateDictionary modelState)
@@ -1420,6 +1422,43 @@ namespace Microsoft.AspNetCore.Mvc
             return new BadRequestObjectResult(modelState);
         }
 
+        /// <summary>
+        /// Creates an <see cref="UnprocessableEntityResult"/> that produces a <see cref="StatusCodes.Status422UnprocessableEntity"/> response.
+        /// </summary>
+        /// <returns>The created <see cref="UnprocessableEntityResult"/> for the response.</returns>
+        [NonAction]
+        public virtual UnprocessableEntityResult UnprocessableEntity()
+        {
+            return new UnprocessableEntityResult();
+        }
+
+        /// <summary>
+        /// Creates an <see cref="UnprocessableEntityObjectResult"/> that produces a <see cref="StatusCodes.Status422UnprocessableEntity"/> response.
+        /// </summary>
+        /// <param name="error">An error object to be returned to the client.</param>
+        /// <returns>The created <see cref="UnprocessableEntityObjectResult"/> for the response.</returns>
+        [NonAction]
+        public virtual UnprocessableEntityObjectResult UnprocessableEntity(object error)
+        {
+            return new UnprocessableEntityObjectResult(error);
+        }
+
+        /// <summary>
+        /// Creates an <see cref="UnprocessableEntityObjectResult"/> that produces a <see cref="StatusCodes.Status422UnprocessableEntity"/> response.
+        /// </summary>
+        /// <param name="modelState">The model state dictionary containing errors to be returned to the client.</param>
+        /// <returns>The created <see cref="UnprocessableEntityObjectResult"/> for the response.</returns>
+        [NonAction]
+        public virtual UnprocessableEntityObjectResult UnprocessableEntity(ModelStateDictionary modelState)
+        {
+            if (modelState == null)
+            {
+                throw new ArgumentNullException(nameof(modelState));
+            }
+
+            return new UnprocessableEntityObjectResult(modelState);
+        }
+
         /// <summary>
         /// Creates an <see cref="BadRequestObjectResult"/> that produces a <see cref="StatusCodes.Status400BadRequest"/> response.
         /// </summary>

src/Microsoft.AspNetCore.Mvc.Core/UnprocessableEntityObjectResult.cs

@@ -0,0 +1,33 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc.ModelBinding;
+
+namespace Microsoft.AspNetCore.Mvc
+{
+    /// <summary>
+    /// An <see cref="ObjectResult"/> that when executed will produce a Unprocessable Entity (422) response.
+    /// </summary>
+    public class UnprocessableEntityObjectResult : ObjectResult
+    {
+        /// <summary>
+        /// Creates a new <see cref="UnprocessableEntityObjectResult"/> instance.
+        /// </summary>
+        /// <param name="modelState"><see cref="ModelStateDictionary"/> containing the validation errors.</param>
+        public UnprocessableEntityObjectResult(ModelStateDictionary modelState)
+            : this(new SerializableError(modelState))
+        {
+        }
+
+        /// <summary>
+        /// Creates a new <see cref="UnprocessableEntityObjectResult"/> instance.
+        /// </summary>
+        /// <param name="error">Contains errors to be returned to the client.</param>
+        public UnprocessableEntityObjectResult(object error)
+            : base(error)
+        {
+            StatusCode = StatusCodes.Status422UnprocessableEntity;
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Core/UnprocessableEntityResult.cs

@@ -0,0 +1,22 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Http;
+
+namespace Microsoft.AspNetCore.Mvc
+{
+    /// <summary>
+    /// A <see cref="StatusCodeResult"/> that when
+    /// executed will produce a Unprocessable Entity (422) response.
+    /// </summary>
+    public class UnprocessableEntityResult : StatusCodeResult
+    {
+        /// <summary>
+        /// Creates a new <see cref="UnprocessableEntityResult"/> instance.
+        /// </summary>
+        public UnprocessableEntityResult()
+            : base(StatusCodes.Status422UnprocessableEntity)
+        {
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Core.Test/ControllerBaseTest.cs

@@ -1990,6 +1990,52 @@ namespace Microsoft.AspNetCore.Mvc.Core.Test
             Assert.Empty(errors);
         }
 
+        [Fact]
+        public void UnprocessableEntity_SetsStatusCode()
+        {
+            // Arrange
+            var controller = new TestableController();
+
+            // Act
+            var result = controller.UnprocessableEntity();
+
+            // Assert
+            Assert.IsType<UnprocessableEntityResult>(result);
+            Assert.Equal(StatusCodes.Status422UnprocessableEntity, result.StatusCode);
+        }
+
+        [Fact]
+        public void UnprocessableEntity_SetsStatusCodeAndValue_Object()
+        {
+            // Arrange
+            var controller = new TestableController();
+            var obj = new object();
+
+            // Act
+            var result = controller.UnprocessableEntity(obj);
+
+            // Assert
+            Assert.IsType<UnprocessableEntityObjectResult>(result);
+            Assert.Equal(StatusCodes.Status422UnprocessableEntity, result.StatusCode);
+            Assert.Equal(obj, result.Value);
+        }
+
+        [Fact]
+        public void UnprocessableEntity_SetsStatusCodeAndValue_ModelState()
+        {
+            // Arrange
+            var controller = new TestableController();
+
+            // Act
+            var result = controller.UnprocessableEntity(new ModelStateDictionary());
+
+            // Assert
+            Assert.IsType<UnprocessableEntityObjectResult>(result);
+            Assert.Equal(StatusCodes.Status422UnprocessableEntity, result.StatusCode);
+            var errors = Assert.IsType<SerializableError>(result.Value);
+            Assert.Empty(errors);
+        }
+
         [Theory]
         [MemberData(nameof(PublicNormalMethodsFromControllerBase))]
         public void NonActionAttribute_IsOnEveryPublicNormalMethodFromControllerBase(MethodInfo method)

test/Microsoft.AspNetCore.Mvc.Core.Test/UnprocessableEntityObjectResultTests.cs

@@ -0,0 +1,36 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc.ModelBinding;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc
+{
+    public class UnprocessableEntityObjectResultTests
+    {
+        [Fact]
+        public void UnprocessableEntityObjectResult_SetsStatusCodeAndValue()
+        {
+            // Arrange & Act
+            var obj = new object();
+            var result = new UnprocessableEntityObjectResult(obj);
+
+            // Assert
+            Assert.Equal(StatusCodes.Status422UnprocessableEntity, result.StatusCode);
+            Assert.Equal(obj, result.Value);
+        }
+
+        [Fact]
+        public void UnprocessableEntityObjectResult_ModelState_SetsStatusCodeAndValue()
+        {
+            // Arrange & Act
+            var result = new UnprocessableEntityObjectResult(new ModelStateDictionary());
+
+            // Assert
+            Assert.Equal(StatusCodes.Status422UnprocessableEntity, result.StatusCode);
+            var errors = Assert.IsType<SerializableError>(result.Value);
+            Assert.Empty(errors);
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Core.Test/UnprocessableEntityResultTests.cs

@@ -0,0 +1,21 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Http;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc
+{
+    public class UnprocessableEntityResultTests
+    {
+        [Fact]
+        public void UnprocessableEntityResult_InitializesStatusCode()
+        {
+            // Arrange & act
+            var result = new UnprocessableEntityResult();
+
+            // Assert
+            Assert.Equal(StatusCodes.Status422UnprocessableEntity, result.StatusCode);
+        }
+    }
+}