Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/System.Web/ModelBinding/KeyValuePairModelBinder`2.cs

@@ -0,0 +1,36 @@
+namespace System.Web.ModelBinding {
+    using System.Collections.Generic;
+
+    public sealed class KeyValuePairModelBinder<TKey, TValue> : IModelBinder {
+
+        private ModelMetadataProvider _metadataProvider;
+
+        internal ModelMetadataProvider MetadataProvider {
+            get {
+                if (_metadataProvider == null) {
+                    _metadataProvider = ModelMetadataProviders.Current;
+                }
+                return _metadataProvider;
+            }
+            set {
+                _metadataProvider = value;
+            }
+        }
+
+        public bool BindModel(ModelBindingExecutionContext modelBindingExecutionContext, ModelBindingContext bindingContext) {
+            ModelBinderUtil.ValidateBindingContext(bindingContext, typeof(KeyValuePair<TKey, TValue>), true /* allowNullModel */);
+
+            TKey key;
+            bool keyBindingSucceeded = KeyValuePairModelBinderUtil.TryBindStrongModel<TKey>(modelBindingExecutionContext, bindingContext, "key", MetadataProvider, out key);
+
+            TValue value;
+            bool valueBindingSucceeded = KeyValuePairModelBinderUtil.TryBindStrongModel<TValue>(modelBindingExecutionContext, bindingContext, "value", MetadataProvider, out value);
+
+            if (keyBindingSucceeded && valueBindingSucceeded) {
+                bindingContext.Model = new KeyValuePair<TKey, TValue>(key, value);
+            }
+            return keyBindingSucceeded || valueBindingSucceeded;
+        }
+
+    }
+}