Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Web.Extensions/ui/WebControls/LinqDataSourceHelper.cs

@@ -0,0 +1,47 @@
+namespace System.Web.UI.WebControls {
+    using System.Collections;
+    using System.Collections.Generic;
+
+    internal class LinqDataSourceHelper {
+
+        public static bool EnumerableContentEquals(IEnumerable enumerableA, IEnumerable enumerableB) {
+            IEnumerator enumeratorA = enumerableA.GetEnumerator();
+            IEnumerator enumeratorB = enumerableB.GetEnumerator();
+            while (enumeratorA.MoveNext()) {
+                if (!enumeratorB.MoveNext())
+                    return false;
+                object itemA = enumeratorA.Current;
+                object itemB = enumeratorB.Current;
+                if (itemA == null) {
+                    if (itemB != null)
+                        return false;
+                }
+                else if (!itemA.Equals(itemB))
+                    return false;
+            }
+            if (enumeratorB.MoveNext())
+                return false;
+            return true;
+        }
+
+        public static Type FindGenericEnumerableType(Type type) {
+            // Logic taken from Queryable.AsQueryable which accounts for Array types which are not
+            // generic but implement the generic IEnumerable interface.
+            while ((type != null) && (type != typeof(object)) && (type != typeof(string))) {
+                if (type.IsGenericType && (type.GetGenericTypeDefinition() == typeof(IEnumerable<>))) {
+                    return type;
+                }
+                foreach (Type interfaceType in type.GetInterfaces()) {
+                    Type genericInterface = FindGenericEnumerableType(interfaceType);
+                    if (genericInterface != null) {
+                        return genericInterface;
+                    }
+                }
+                type = type.BaseType;
+            }
+            return null;
+        }
+
+    }
+
+}