Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/System.Web.DynamicData/DynamicData/Util/DefaultValueMapping.cs

@@ -0,0 +1,32 @@
+namespace System.Web.DynamicData.Util {
+    using System.Collections.Generic;
+    using System.ComponentModel;
+    using System.Diagnostics;
+
+    internal class DefaultValueMapping {
+        private IDictionary<string, object> _defaultValues;
+
+        public DictionaryCustomTypeDescriptor Instance {
+            get;
+            private set;
+        }
+
+        public IDictionary<string, object> Values {
+            get {
+                return _defaultValues;
+            }
+        }
+
+        public DefaultValueMapping(IDictionary<string, object> defaultValues) {
+            Debug.Assert(defaultValues != null);
+            _defaultValues = defaultValues;
+            // Build a custom type descriptor which will act as a lightweight wrapper around the dictionary.
+            Instance = new DictionaryCustomTypeDescriptor(defaultValues);
+        }
+
+        public bool Contains(MetaColumn column) {
+            Debug.Assert(_defaultValues != null);
+            return Misc.IsColumnInDictionary(column, _defaultValues);
+        }
+    }
+}