LINQ to SQL as databinding source for WPF Treeview

I wonder if someone could provide a simple example of the following. (preferably in VB.Net):

I have an SQL database with related tables and I am successfully using LINQ to SQL in other areas of my application, but am a little stuck with the Heirarchical Treeview.

I would simply like to use a LINQ query from the database as a source for a WPF Treeview. If I can set the ItemsSource for the treeview as my LINQ result and just set the databinding for treeview items to the various columns that would make my day, but I cant seem to get it cooking.

After spending hours searching the net, I can't find many examples that show this very simply at all. I have found similar ideas but nothing simple and specific for a newbie like myself.

As far as I understand, the relationships defined in the DBML file should stay intact when executing the LINQ query. So, can I have something like this as the ItemsSource for the Treeview?

Dim pdc As New ProjectDataContext()  
Public Property Selection() As Integer

Dim tree = From c In pdc.Customers _
           Where c.CustomerID = _Selection _
           Select c

projecttreeview.ItemsSource = tree

Then, the databinding for the TreeView Items could just be {Binding CustomerName) for a parent node and say {Binding Orders.OrderName} as a child node. eg:

<TreeView Name="projecttreeview">
  <TreeView.ItemTemplate>
    <HierarchicalDataTemplate ItemsSource="{Binding Customers}">
      <TextBlock.Text="Binding CustomerName}"/>
        <HierarchicalDataTemplate.ItemTemplate>
          <DataTemplate>
            <TextBlock.Text="{Binding Orders.OrderName}"/>
          </DataTemplate>
        </HierarchicalDataTemplate.ItemTemplate>
      </HierarchicalDataTemplate>
    </TreeView.ItemTemplate>
</TreeView>

Obviously this is not quite working out as simply as I would like. Any pointers would be greatly appreciated.

From stackoverflow

• First of all, let me to clarify one issue you probably will run into: when you use query as an ItemsSource, then the ItemsControl won't reflect any changes after you will rerun the query, so, assigning the ItemsSource to a query is very similar to assigning it to the query result converted to an array.

  Second, to access related objects/collections (wherever you do it from - would it be a DataTemplate or simply plain code) you have to explicitly point it out when you creating a query. In Entity Framework you would probably do that by means of Include method like this: treeview.ItemsSource = tree.Include("Orders") - it will force the engine to make JOIN SQL query over the database.

  archimed7592 : P.S. I don't actually know LINQ to SQL, so you have to read MSDN for the correct method to include related object, but the "pointer" has been given :)

  yimbot : Thanks for the tip, I had a feeling there was an issue with the other tables not being seen properly. Investigating the best way to use the "Include" statement which seems to be a little minefield of it's own...

  archimed7592 : Look at Relationships topic in [this](http://msdn.microsoft.com/en-us/library/bb425822.aspx#linqtosql_topic11) tutorial - there are some samples how to do that. Something like this: DataShape ds = new DataShape(); ds.LoadWith(c => c.Orders); db.Shape = ds; var q = from c in db.Customers where c.City == "London" select c; HTH.

  yimbot : For anyone following this thread in the future, I have found some very useful information here: http://www.scip.be/index.php?Page=ArticlesNET09 Thanks archimed7592 for steering me in the right direction!