well advancing but not done yet :)

2018-03-26 21:30:36 -05:00
parent dcd251f199
commit 14f1091eb8
4 changed files with 89 additions and 12 deletions
@@ -16,10 +16,58 @@ namespace PoweredSoft.DynamicLinq.ConsoleApp
        {
            var type = typeof(Dal.Pocos.Author);
            var param = Expression.Parameter(type);
-            var path = "Posts.Comments.Id";
+            var parts = ExpressionPathPart.Split(param, "Posts.Comments.Id");

-            var parts = ExpressionPathPart.Break(param, "Posts.Comments.Id");
+            // add the last part.
+            var parent = parts.Last();
+            var toListType = parent.GetToListType();
+            parts.Add(new ExpressionPathPart
+            {
+                ParentExpression = parent.PartExpression,
+                PartExpression = Expression.Call(typeof(Enumerable), "ToList", new[] { toListType }, parent.ParentExpression)
+            });

+            var result = CreateSelectExpressionFromParts(parts, SelectCollectionHandling.Flatten, SelectNullHandling.New);
+        }
+
+        public static Expression CreateSelectExpressionFromParts(List<ExpressionPathPart> parts, 
+            SelectCollectionHandling selectCollectionHandling = SelectCollectionHandling.LeaveAsIs, 
+            SelectNullHandling nullChecking = SelectNullHandling.LeaveAsIs)
+        {
+            Type nullHandlingRightType = null;
+            Expression nullHandlingNullValue = null;
+
+            if (nullChecking != SelectNullHandling.LeaveAsIs)
+            {
+                nullHandlingRightType = parts.Last().PartExpression.Type;
+                nullHandlingNullValue = nullChecking == SelectNullHandling.Default
+                    ? Expression.Default(nullHandlingRightType) as Expression
+                    : Expression.New(nullHandlingRightType) as Expression;
+            }
+
+            // reversed :)
+            var reversedCopy = parts.Select(t => t).ToList();
+            reversedCopy.Reverse();
+
+            Expression ret = null;
+            reversedCopy.ForEach(t =>
+            {
+                if (t.IsParentGenericEnumerable())
+                {
+                    var lambda = t.GetLambdaExpression();
+                    var parentGenericType = t.ParentGenericEnumerableType();
+                    if (selectCollectionHandling == SelectCollectionHandling.LeaveAsIs || !t.IsGenericEnumerable())
+                        ret = Expression.Call(typeof(Enumerable), "Select", new Type[] { parentGenericType, t.PartExpression.Type }, t.ParentExpression, lambda);
+                    else
+                        ret = Expression.Call(typeof(Enumerable), "SelectMany", new Type[] { parentGenericType, t.GenericEnumerableType() }, t.ParentExpression, lambda);
+                }
+                else
+                {
+                    ret = t.PartExpression;
+                }
+            });
+            
+            return ret;
        }