Why is my WPF Treeview bound to LinqToSql classes being a memory hog?

Question

I have a WPF App which is grinding to a halt after running out of memory...
It is basically a TreeView displaying nodes, which are instances of Linq To Sql OR Generated class ICTemplates.Segment. There around 20 tables indirectly linked via associations to this class in the OR designer.

<TreeView Grid.Column="0" x:Name="tvwSegments" 
                      ItemsSource="{Binding}" 
                      SelectedItemChanged="OnNewSegmentSelected"/>
<HierarchicalDataTemplate DataType="{x:Type local:Segment}" ItemsSource="{Binding Path=Children}"> 
...

// code behind, set the data context based on user-input (Site, Id)
KeeperOfControls.DataContext = from segment in tblSegments
   where segment.site == iTemplateSite && segment.id == iTemplateSid
   select segment;

I've added an explicit property called Children to the segment class which looks up another table with parent-child records.

public IEnumerable<Segment> Children
{
  get
  {
    System1ConfigDataContext dc = new System1ConfigDataContext();
    return from link in this.ChildLinks
      join segment in dc.Segments on new { Site = link.ChildSite, ID = link.ChildSID } equals new { Site = segment.site, ID = segment.id }
      select segment;
  }
}

The rest of it is data binding coupled with data templates to display each Segment as a set of UI Controls.

I'm pretty certain that the children are being loaded on-demand (when I expand the parent) going by the response time. When I expand a node with around 70 children, it takes a while before the children are loaded (Task manager shows Mem Usage as 1000000K!). If I expand the next node with around 50 children, BOOM! OutOfMemoryException

I ran the VS Profiler to dig deeper and here are the results

Summary Page Object Lifetimes Allocation

The top 3 are Action, DeferredSourceFactory.DeferredSource and EntitySet (all .Net/LINQ classes). The only user-classes are Segment[] and Segment come in at #9 an #10.

I can't think of a lead to pursue.. What could be the reason ?

Answer 1

Have you tried using a global DataContext instead of one for each element?

Creating all of the DataContext's each with there own query and results could be the cause of your memory bloat.

Answer 2

I don't know the exact solution but the new statement in join may cause this. Because for each relation a new object could be created(But as I mentioned, I don't know if it is correct).

Could you try this;

public IEnumerable<Segment> Children
{
  get
  {
    System1ConfigDataContext dc = new System1ConfigDataContext();
    return from link in this.ChildLinks
      join segment in dc.Segments on link.ChildSite == segment.site && link.ChildSID == segment.id
      select segment;
  }
}

Answer 3

maybe a using surrounding that DataContext ?

using(System1ConfigDataContext dc = new System1ConfigDataContext()){
  .... ?
}

also, have you tried using an sql profiler? might shed some light on the matter.