Fixed validation of ParentId for recursive Save()

When doing a recursive `Save()`, the `ParentID` attribute of each child topic was being validated to ensure that it had correctly been set to a positive number—i.e., that the parent's `Id` had been properly set from the database. There were two issues with this. First, we really only need to check that once, when the `topic.Id` is set, not for each child. Second, it was being checked _prior_ to the `ParentID` being set on the child. While I was at it, I set the `ParentID` based on `topic.Id` not `returnVal`; these will be the same, but the semantics are a bit clearer.

Author: JeremyCaney

OnTopic.Data.Sql/SqlTopicRepository.cs

@@ -796,6 +796,11 @@ public override int Save([NotNull]Topic topic, bool isRecursive = false, bool is
 
         topic.Id = returnVal;
 
+        Contract.Assume<InvalidOperationException>(
+          topic.Id > 0,
+          "The call to the CreateTopic stored procedure did not return the expected 'Id' parameter."
+        );
+
         /*----------------------------------------------------------------------------------------------------------------------
         | Add version to version history
         \---------------------------------------------------------------------------------------------------------------------*/
@@ -827,16 +832,13 @@ public override int Save([NotNull]Topic topic, bool isRecursive = false, bool is
         if (attributes != null) attributes.Dispose();
       }
 
+
       /*------------------------------------------------------------------------------------------------------------------------
       | Recurse
       \-----------------------------------------------------------------------------------------------------------------------*/
       if (isRecursive) {
         foreach (var childTopic in topic.Children) {
-          Contract.Assume<InvalidOperationException>(
-            childTopic.Attributes.GetInteger("ParentID", -1) > 0,
-            "The call to the CreateTopic stored procedure did not return the expected 'ParentID' parameter."
-          );
-          childTopic.Attributes.SetValue("ParentID", returnVal.ToString(CultureInfo.InvariantCulture));
+          childTopic.Attributes.SetValue("ParentID", topic.Id.ToString(CultureInfo.InvariantCulture));
           Save(childTopic, isRecursive, isDraft);
         }
       }