better expression logic should be easier to implement null checks now ;)

PoweredSoft.DynamicLinq/Parser/ExpressionParser.cs

@@ -62,10 +62,11 @@ namespace PoweredSoft.DynamicLinq.Parser
             });
         }
 
-        private ExpressionParserPieceGroup CreateAndAddGroup(List<ExpressionParserPieceGroup> groups, ParameterExpression parameter)
+        private ExpressionParserPieceGroup CreateAndAddGroup(List<ExpressionParserPieceGroup> groups, ParameterExpression parameter, ExpressionParserPieceGroup parent)
         {
             var group = new ExpressionParserPieceGroup();
-            group.ParameterExpression = parameter;
+            group.Parameter = parameter;
+            group.Parent = parent;
             groups.Add(group);
             return group;
         }
@@ -74,12 +75,12 @@ namespace PoweredSoft.DynamicLinq.Parser
         {
             var groups = new List<ExpressionParserPieceGroup>();
 
-            var group = CreateAndAddGroup(groups, Parameter);
+            var group = CreateAndAddGroup(groups, Parameter, null);
             Pieces.ForEach(piece =>
             {
                 group.Pieces.Add(piece);
                 if (piece.IsGenericEnumerable)
-                    group = CreateAndAddGroup(groups, Expression.Parameter(piece.EnumerableType));
+                    group = CreateAndAddGroup(groups, Expression.Parameter(piece.EnumerableType), group);
             });
 
             return groups;

PoweredSoft.DynamicLinq/Parser/ExpressionParserPieceGroup.cs

@@ -9,10 +9,11 @@ namespace PoweredSoft.DynamicLinq.Parser
     public class ExpressionParserPieceGroup
     {
         public List<ExpressionParserPiece> Pieces { get; set; } = new List<ExpressionParserPiece>();
-        public ParameterExpression ParameterExpression { get; set; }
+        public ParameterExpression Parameter { get; set; }
+        public ExpressionParserPieceGroup Parent { get; set; }
 
 #if DEBUG
-        public override string ToString() => $"{ParameterExpression?.ToString()} is {ParameterExpression?.Type} | {(Pieces == null ? "" : string.Join(" -> ", Pieces.Select(t2 => t2.ToString())))}";
+        public override string ToString() => $"{Parameter?.ToString()} is {Parameter?.Type} | {(Pieces == null ? "" : string.Join(" -> ", Pieces.Select(t2 => t2.ToString())))}";
 
         public object CompileSimpleExpress(SelectNullHandling nullHandling)
         {

PoweredSoft.DynamicLinq/Parser/ParserExtensions.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Linq.Expressions;
 using System.Text;
 
@@ -13,16 +14,19 @@ namespace PoweredSoft.DynamicLinq.Parser
             return result;
         }
 
-        public static LambdaExpression CompileGroup(this ExpressionParserPieceGroup group, SelectNullHandling NullHandling)
+        public static Expression CompileGroup(this ExpressionParserPieceGroup group, SelectNullHandling NullHandling)
         {
-            var expr = group.ParameterExpression as Expression;
+            var expr = group.Parameter as Expression;
             group.Pieces.ForEach(piece =>
             {
                 expr = Expression.PropertyOrField(expr, piece.Name);
             });
+            return expr;
+        }
 
-            var ret = Expression.Lambda(expr, group.ParameterExpression);
-            return ret;
+        public static Type GroupEnumerableType(this ExpressionParserPieceGroup group)
+        {
+            return group.Pieces.Last().EnumerableType;
         }
     }
 }