Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/System.Data.Linq/SubqueryRules.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.Reflection;
+using System.Linq.Expressions;
+
+namespace System.Data.Linq {
+    /// <summary>
+    /// Encodes the rules for subqueries.
+    /// </summary>
+    static class SubqueryRules {
+        /// <summary>
+        /// This list of top-level methods that are supported in subqueries.
+        /// </summary>
+        /// <param name="mi"></param>
+        /// <returns></returns>
+        static internal bool IsSupportedTopLevelMethod(MethodInfo mi) {
+            if (!IsSequenceOperatorCall(mi))
+                return false;
+            switch (mi.Name) {
+                case "Where":
+                case "OrderBy":
+                case "OrderByDescending":
+                case "ThenBy":
+                case "ThenByDescending":
+                case "Take":
+                    return true;
+            }
+            return false;
+        }
+        private static bool IsSequenceOperatorCall(MethodInfo mi) {
+            Type declType = mi.DeclaringType;
+            if (declType == typeof(System.Linq.Enumerable) ||
+                declType == typeof(System.Linq.Queryable)) {
+                return true;
+            }
+            return false;
+        }
+    }
+}