Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Web/UI/WebControls/QueryExtensions.cs

@@ -0,0 +1,47 @@
+using System.Linq;
+using System.Linq.Expressions;
+
+namespace System.Web.UI.WebControls {
+    public static class QueryExtensions {
+
+        private const string SORT_DIRECTION_DESC = " DESC";
+
+        public static IQueryable<T> SortBy<T>(this IQueryable<T> source, string sortExpression) where T : class {
+
+            if (source == null) {
+                throw new ArgumentNullException("source");
+            }
+
+            if (String.IsNullOrWhiteSpace(sortExpression)) {
+                return source;
+            }
+
+            sortExpression = sortExpression.Trim();
+            bool isDescending = false;
+
+            // DataSource control passes the sort parameter with a direction
+            // if the direction is descending
+            if (sortExpression.EndsWith(SORT_DIRECTION_DESC, StringComparison.OrdinalIgnoreCase)) {
+                isDescending = true;
+                int descIndex = sortExpression.Length - SORT_DIRECTION_DESC.Length;
+                sortExpression = sortExpression.Substring(0, descIndex).Trim();
+            }
+
+            if (String.IsNullOrEmpty(sortExpression)) {
+                return source;
+            }
+
+            ParameterExpression parameter = Expression.Parameter(source.ElementType, String.Empty);
+            MemberExpression property = Expression.Property(parameter, sortExpression);
+            LambdaExpression lambda = Expression.Lambda(property, parameter);
+
+            string methodName = (isDescending) ? "OrderByDescending" : "OrderBy" ;
+
+            Expression methodCallExpression = Expression.Call(typeof(Queryable), methodName,
+                                                new Type[] { source.ElementType, property.Type },
+                                                source.Expression, Expression.Quote(lambda));
+
+            return (IQueryable<T>)source.Provider.CreateQuery(methodCallExpression);
+        }
+    }
+}