Add FormatterCollection<T>

#2945

src/Microsoft.AspNet.Mvc.Core/Formatters/FormatterCollection.cs

@@ -0,0 +1,31 @@
+// 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 System.Collections.ObjectModel;
+
+namespace Microsoft.AspNet.Mvc.Formatters
+{
+    /// <summary>
+    /// Represents a collection of formatters.
+    /// </summary>
+    /// <typeparam name="TFormatter">The type of formatters in the collection.</typeparam>
+    public class FormatterCollection<TFormatter> : Collection<TFormatter>
+    {
+
+        /// <summary>
+        /// Removes all formatters of the specified type.
+        /// </summary>
+        /// <typeparam name="T">The type to remove.</typeparam>
+        public void RemoveType<T>() where T : TFormatter
+        {
+            for (var i = Count - 1; i >= 0; i--)
+            {
+                var formatter = this[i];
+                if (formatter is T)
+                {
+                    RemoveAt(i);
+                }
+            }
+        }
+    }
+}

src/Microsoft.AspNet.Mvc.Core/MvcOptions.cs

@@ -25,8 +25,8 @@ public MvcOptions()
             Conventions = new List<IApplicationModelConvention>();
             Filters = new FilterCollection();
             FormatterMappings = new FormatterMappings();
-            InputFormatters = new List<IInputFormatter>();
-            OutputFormatters = new List<IOutputFormatter>();
+            InputFormatters = new FormatterCollection<IInputFormatter>();
+            OutputFormatters = new FormatterCollection<IOutputFormatter>();
             ModelBinders = new List<IModelBinder>();
             ModelMetadataDetailsProviders = new List<IMetadataDetailsProvider>();
             ModelValidatorProviders = new List<IModelValidatorProvider>();
@@ -61,7 +61,7 @@ public MvcOptions()
         /// <summary>
         /// Gets a list of <see cref="IInputFormatter"/>s that are used by this application.
         /// </summary>
-        public IList<IInputFormatter> InputFormatters { get; }
+        public FormatterCollection<IInputFormatter> InputFormatters { get; }
 
         /// <summary>
         /// Gets or sets the maximum number of validation errors that are allowed by this application before further
@@ -109,7 +109,7 @@ public int MaxModelValidationErrors
         /// <summary>
         /// Gets a list of <see cref="IOutputFormatter"/>s that are used by this application.
         /// </summary>
-        public IList<IOutputFormatter> OutputFormatters { get; }
+        public FormatterCollection<IOutputFormatter> OutputFormatters { get; }
 
         /// <summary>
         /// Gets or sets the flag which causes content negotiation to ignore Accept header 

test/Microsoft.AspNet.Mvc.Core.Test/Formatters/FormatterCollectionTest.cs

@@ -0,0 +1,47 @@
+// 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 System;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace Microsoft.AspNet.Mvc.Formatters
+{
+    public class FormatterCollectionTest
+    {
+        [Fact]
+        public void RemoveType_RemovesAllOfType()
+        {
+            // Arrange
+            var collection = new FormatterCollection<IOutputFormatter>
+            {
+                new TestOutputFormatter(),
+                new AnotherTestOutputFormatter(),
+                new TestOutputFormatter()
+            };
+
+            // Act
+            collection.RemoveType<TestOutputFormatter>();
+
+            // Assert
+            var formatter = Assert.Single(collection);
+            Assert.IsType(typeof(AnotherTestOutputFormatter), formatter);
+        }
+
+        private class TestOutputFormatter : OutputFormatter
+        {
+            public override Task WriteResponseBodyAsync(OutputFormatterContext context)
+            {
+                throw new NotImplementedException();
+            }
+        }
+
+        private class AnotherTestOutputFormatter : OutputFormatter
+        {
+            public override Task WriteResponseBodyAsync(OutputFormatterContext context)
+            {
+                throw new NotImplementedException();
+            }
+        }
+    }
+}