well advancing but not done yet :)

PoweredSoft.DynamicLinq.ConsoleApp/Program.cs

@@ -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;
         }
 
 

PoweredSoft.DynamicLinq/Constants.cs

@@ -59,6 +59,13 @@ namespace PoweredSoft.DynamicLinq
         Flatten
     }
 
+    public enum SelectNullHandling
+    {
+        LeaveAsIs,
+        Default,
+        New
+    }
+
     internal static class Constants
     {
         internal static readonly MethodInfo GroupByMethod = typeof(Queryable).GetMethods().First(t => t.Name == "GroupBy");

PoweredSoft.DynamicLinq/ExpressionPathPart.cs

@@ -8,13 +8,18 @@ namespace PoweredSoft.DynamicLinq.Helpers
     public class ExpressionPathPart
     {
         public Expression ParentExpression { get; set; }
-        public Expression Expression { get; set; }
+        public ParameterExpression ParameterExpression { get; set; }
-        public bool IsNullable() => TypeHelpers.IsNullable(Expression.Type);
+        public Expression PartExpression { get; set; }
-        public bool IsParentParamaterExpression() => ParentExpression is ParameterExpression;
-        public bool IsGenericEnumerable() => QueryableHelpers.IsGenericEnumerable(Expression);
-        public Type GenericEnumerableType() => Expression.Type.GenericTypeArguments.First();
 
-        public static List<ExpressionPathPart> Break(ParameterExpression param, string path)
+        public bool IsNullable() => TypeHelpers.IsNullable(PartExpression.Type);
+   
+        public bool IsGenericEnumerable() => QueryableHelpers.IsGenericEnumerable(PartExpression);
+        public Type GenericEnumerableType() => PartExpression.Type.GenericTypeArguments.First();
+        public bool IsCallingMethod() => PartExpression is MethodCallExpression;
+        public Type GetToListType() => IsGenericEnumerable() ? GenericEnumerableType() : PartExpression.Type;
+        public bool IsParentGenericEnumerable() => QueryableHelpers.IsGenericEnumerable(ParentExpression);
+
+        public static List<ExpressionPathPart> Split(ParameterExpression param, string path)
         {
             var ret = new List<ExpressionPathPart>();
 
@@ -23,14 +28,31 @@ namespace PoweredSoft.DynamicLinq.Helpers
             parts.ForEach(part =>
             {
                 var p = new ExpressionPathPart();
-                p.Expression = Expression.PropertyOrField(parent, part);
+                p.PartExpression = Expression.PropertyOrField(parent, part);
                 p.ParentExpression = parent;
+                p.ParameterExpression = param;
                 ret.Add(p);
 
-                parent = p.IsGenericEnumerable() ? Expression.Parameter(p.GenericEnumerableType()) : p.Expression;
+                if (p.IsGenericEnumerable())
+                {
+                    param = Expression.Parameter(p.GenericEnumerableType());
+                    parent = param;
+                }
+                else
+                {
+                    parent = p.PartExpression;
+                }
             });
 
             return ret;
         }
+
+        public LambdaExpression GetLambdaExpression()
+        {
+            var lambda = Expression.Lambda(PartExpression, ParameterExpression);
+            return lambda;
+        }
+
+        public Type ParentGenericEnumerableType() => ParentExpression.Type.GenericTypeArguments.First();
     }
 }

PoweredSoft.DynamicLinq/Helpers/QueryableHelpers.cs

@@ -296,11 +296,11 @@ namespace PoweredSoft.DynamicLinq.Helpers
         /// <returns></returns>
         public static Expression ResolvePathForExpression(ParameterExpression param, string path)
         {
-            var parts = ExpressionPathPart.Break(param, path);
+            var parts = ExpressionPathPart.Split(param, path);
             if (parts.Any(t => t.IsGenericEnumerable()))
                 throw new Exception("this method does not support collection handling");
 
-            return parts.Last().Expression;
+            return parts.Last().PartExpression;
         }
 
         public static ConstantExpression GetConstantSameAsLeftOperator(Expression member, object value)