From 62fa1a4d21d69064e387df53315a32c07a775c51 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?David=20Leb=C3=A9e?= <DavidLebee@roxboro.biz>
Date: Sat, 14 Apr 2018 23:26:42 -0500
Subject: [PATCH] better handling of null and simple expression null checking.

---
 PoweredSoft.DynamicLinq.ConsoleApp/Program.cs     |  2 +-
 PoweredSoft.DynamicLinq.Test/SelectTests.cs       |  4 +++-
 .../Helpers/QueryableHelpers.cs                   |  6 +++++-
 .../Resolver/PathExpressionResolver.cs            | 15 +++++++++++----
 4 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/PoweredSoft.DynamicLinq.ConsoleApp/Program.cs b/PoweredSoft.DynamicLinq.ConsoleApp/Program.cs
index a933f2d..2fc0be0 100644
--- a/PoweredSoft.DynamicLinq.ConsoleApp/Program.cs
+++ b/PoweredSoft.DynamicLinq.ConsoleApp/Program.cs
@@ -15,7 +15,7 @@ namespace PoweredSoft.DynamicLinq.ConsoleApp
         static void Main(string[] args)
         {
             var selectTests = new SelectTests();
-            selectTests.SelectNullChecking();
+            selectTests.SelectNullChecking2();
         }
 
     }
diff --git a/PoweredSoft.DynamicLinq.Test/SelectTests.cs b/PoweredSoft.DynamicLinq.Test/SelectTests.cs
index 531c2b5..36bd62f 100644
--- a/PoweredSoft.DynamicLinq.Test/SelectTests.cs
+++ b/PoweredSoft.DynamicLinq.Test/SelectTests.cs
@@ -82,6 +82,7 @@ namespace PoweredSoft.DynamicLinq.Test
         {
             var query = TestData.Authors.AsQueryable();
 
+            
             var qs = query.Select(t => new
             {
                 CommentLikes = t.Posts == null ? 
@@ -128,7 +129,8 @@ namespace PoweredSoft.DynamicLinq.Test
             {
                 t.NullChecking(true);
                 // this needs to be fixed.
-                t.PathToList("Comment.Post.Comments.CommentText", selectCollectionHandling: SelectCollectionHandling.Flatten);
+                t.Path("Comment.CommentText", "CommentText2");
+                //t.PathToList("Comment.Post.Comments.CommentText", selectCollectionHandling: SelectCollectionHandling.Flatten);
             });
 
             var b = querySelect.ToDynamicClassList();
diff --git a/PoweredSoft.DynamicLinq/Helpers/QueryableHelpers.cs b/PoweredSoft.DynamicLinq/Helpers/QueryableHelpers.cs
index 8fd42f0..a53bf21 100644
--- a/PoweredSoft.DynamicLinq/Helpers/QueryableHelpers.cs
+++ b/PoweredSoft.DynamicLinq/Helpers/QueryableHelpers.cs
@@ -208,7 +208,11 @@ namespace PoweredSoft.DynamicLinq.Helpers
         {
             if (selectType == SelectTypes.Path)
             {
-                return ResolvePathForExpression(parameter, path);
+                var parser = new ExpressionParser(parameter, path);
+                var resolver = new PathExpressionResolver(parser);
+                resolver.NullChecking = nullChecking;
+                resolver.Resolve();
+                return resolver.GetResultBodyExpression();
             }
             else if (selectType == SelectTypes.PathToList)
             {
diff --git a/PoweredSoft.DynamicLinq/Resolver/PathExpressionResolver.cs b/PoweredSoft.DynamicLinq/Resolver/PathExpressionResolver.cs
index a59b425..9871beb 100644
--- a/PoweredSoft.DynamicLinq/Resolver/PathExpressionResolver.cs
+++ b/PoweredSoft.DynamicLinq/Resolver/PathExpressionResolver.cs
@@ -15,7 +15,6 @@ namespace PoweredSoft.DynamicLinq.Resolver
         public ExpressionParser Parser { get; protected set; }
 
         public Expression Result { get; protected set; }
-        public Type NullType { get; set; }
 
         public PathExpressionResolver(ExpressionParser parser)
         {
@@ -55,7 +54,11 @@ namespace PoweredSoft.DynamicLinq.Resolver
 
                     if (group.Parent == null)
                     {
-                        currentExpression = groupExpressionLambda;
+                        currentExpression = groupExpression;
+                        if (NullChecking != false)
+                            currentExpression = CheckNullOnFirstGroup(group, currentExpression);
+
+                        currentExpression = Expression.Lambda(currentExpression, group.Parameter);
                         continue;
                     }
 
@@ -128,10 +131,14 @@ namespace PoweredSoft.DynamicLinq.Resolver
         {
             var path = string.Join(".", group.Pieces.Select(t => t.Name));
             var whereExpression = QueryableHelpers.CreateConditionExpression(group.Parameter.Type, path,
-                    ConditionOperators.Equal, null, QueryConvertStrategy.ConvertConstantToComparedPropertyOrField,
+                    ConditionOperators.NotEqual, null, QueryConvertStrategy.ConvertConstantToComparedPropertyOrField,
                     parameter: group.Parameter, nullChecking: true);
 
             var whereBodyExpression = (whereExpression as LambdaExpression).Body;
+            whereBodyExpression =Expression.Not(whereBodyExpression);
+
+
+
 
             var nullType = currentExpression.Type;
             Expression ifTrueExpression = null;
@@ -143,7 +150,7 @@ namespace PoweredSoft.DynamicLinq.Resolver
             }
             else
             {
-                ifTrueExpression = Expression.Default(NullType);
+                ifTrueExpression = Expression.Default(nullType);
             }
 
             return Expression.Condition(whereBodyExpression, ifTrueExpression, currentExpression, currentExpression.Type);