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POADO.NET Entity Framework generates unexpected, problem INSERTs
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  1. POADO.NET Entity Framework generates unexpected, problem INSERTs
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    copied!<p>I need some help understanding the ADO.NET Entity Framework.</p> <p>I'm trying to represent and manipulate hierarchical data in a WPF TreeView control with the ADO.NET Entity Framework.</p> <p><a href="http://img14.imageshack.us/img14/7158/thingpi1.gif" rel="nofollow noreferrer">ADO.NET Entity Framework Object with parent and children http://img14.imageshack.us/img14/7158/thingpi1.gif</a></p> <p>Each of these Things has a single parent and zero or more children.</p> <p>My "delete" button...</p> <pre> Private Sub ButtonDeleteThing_Click(...) db.DeleteObject(DirectCast(TreeViewThings.SelectedItem, Thing)) db.SaveChanges() End Sub </pre> <p>I'm monitoring the SQL Server Profiler while I debug my application:</p> <ol> <li>The first button click deletes just fine.</li> <li>The second button click inserts a duplicate parent (but with empty GUID uniqueidentifier primary key) and then performs the delete.</li> <li>The third button click fails (Violation of PRIMARY KEY constraint) because it cannot insert another row with an empty GUID primary key.</li> </ol> <p>The unexpected, generated T-SQL duplication...</p> <pre> exec sp_executesql N'insert [dbo].[Thing]([Id], [ParentId], ...) values (@0, @1, ...) ',N'@0 uniqueidentifier,@1 uniqueidentifier,...', @0='00000000-0000-0000-0000-000000000000', @1='389D987D-79B1-4A9D-970F-CE15F5E3E18A', ... </pre> <p>But, it's not just deletes. My "add" button has similar behavior with unexpected inserts. It follows the same pattern.</p> <p>This makes me think there's a more fundamental problem with how I'm binding these entity classes to the WPF TreeView or with my data model itself.</p> <p>Here's the relevant code...</p> <p>XAML...</p> <pre><code>&lt;TreeView Name="TreeViewThings" ItemsSource="{Binding}" TreeViewItem.Expanded="TreeViewThings_Expanded" TreeViewItem.Selected="TreeViewThings_Selected" ... &gt; &lt;TreeView.Resources&gt; &lt;HierarchicalDataTemplate DataType="{x:Type local:Thing}" ItemsSource="{Binding Children}"&gt; &lt;TextBlock Text="{Binding Path=Title}" /&gt; &lt;/HierarchicalDataTemplate&gt; &lt;/TreeView.Resources&gt; &lt;/TreeView&gt; &lt;Button Name="ButtonAddThing" Content="Add Thing" ... /&gt; &lt;Button Name="ButtonDeleteThing" Content="Delete Thing" ... /&gt; </code></pre> <p>Visual Basic...</p> <pre> Partial Public Class Window1 Dim db As New ThingProjectEntities Private Sub Window1_Loaded(...) Handles MyBase.Loaded TreeViewThings.ItemsSource = _ From t In db.Thing.Include("Children") _ Where (t.Parent Is Nothing) _ Select t End Sub Private Sub TreeViewThings_Expanded(...) Dim ExpandedTreeViewItem As TreeViewItem = _ DirectCast(e.OriginalSource, TreeViewItem) LoadTreeViewChildren(ExpandedTreeViewItem) End Sub Sub LoadTreeViewChildren(ByRef Parent As TreeViewItem) Dim ParentId As Guid = DirectCast(Parent.DataContext, Thing).Id Dim ChildThings As System.Linq.IQueryable(Of Thing) ChildThings = From t In db.Thing.Include("Children") _ Where t.Parent.Id = ParentId _ Select t Parent.ItemsSource = ChildThings End Sub Private Sub ButtonAddThing_Click(...) Dim NewThing As New Thing NewThing.Id = Guid.NewGuid() Dim ParentId As Guid = _ DirectCast(TreeViewThings.SelectedItem, Thing).Id NewThing.Parent = (From t In db.Thing _ Where t.Id = ParentId _ Select t).First ... db.AddToThing(NewThing) db.SaveChanges() TreeViewThings.UpdateLayout() End Sub Private Sub ButtonDeleteThing_Click(...) db.DeleteObject(DirectCast(TreeViewThings.SelectedItem, Thing)) db.SaveChanges() End Sub ... End Class </pre> <p>What am I doing wrong? Why is it generating these strange inserts?</p> <hr> <p>Update:</p> <p>I've made a breakthrough. But, I still can't explain it.</p> <p>I'd gotten rid of the cause when I simplified my code for this question.</p> <p>Rather than using Linq such as:</p> <pre> From t In db.Thing.Include("Children") Where ... </pre> <p>I've been using Linq such as:</p> <pre> From t In db.Thing.Include("Children").Include("Brand") Where ... </pre> <p>You see, My Thing entity is related to another Brand entity.</p> <p><a href="http://img25.imageshack.us/img25/3268/thingbrandct4.gif" rel="nofollow noreferrer">ADO.NET Entity Framework Object with parent and children and a related Object http://img25.imageshack.us/img25/3268/thingbrandct4.gif</a></p> <p>I thought it was irrelevant, so I didn't include it in the question above.</p> <p>Apparently this was the cause of my unexpected, problem inserts in my Thing table.</p> <p>But, why? Can anyone explain why this was happening? I'd like to understand it better.</p>
 

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