RadGrid NestedViewTemplate Generate - System.InvalidOperationException: Collection was modified; enumeration operation may not execute

[Davy]

Hello,

I'm encountering an exception using RadGrid's NestedViewTemplate feature.
If I set HierarchyDefaultExpanded="true" RadGrid, NestedViewTemplate is rendering correctly but all rows are expanded which is not very interesting. So i leave HierarchyDefaultExpanded to false so rows are initially collapsed when i expand a row following exception is raised

[System.InvalidOperationException: Collection was modified; enumeration operation may not execute.]
System.Web.UI.ControlCollectionEnumerator.MoveNext() +8672514
   Telerik.Web.UI.RadFormDecorator.FindAndDecorateControls(Control parent) +639
   Telerik.Web.UI.RadFormDecorator.FindAndDecorateControls(Control parent) +630
   Telerik.Web.UI.RadFormDecorator.FindAndDecorateControls(Control parent) +630
   Telerik.Web.UI.RadFormDecorator.FindAndDecorateControls(Control parent) +630
   Telerik.Web.UI.RadFormDecorator.FindAndDecorateControls(Control parent) +630
   Telerik.Web.UI.RadFormDecorator.FindAndDecorateControls(Control parent) +630
   Telerik.Web.UI.RadFormDecorator.FindAndDecorateControls(Control parent) +630
   Telerik.Web.UI.RadFormDecorator.FindAndDecorateControls(Control parent) +630
   Telerik.Web.UI.RadFormDecorator.FindAndDecorateControls(Control parent) +630
   Telerik.Web.UI.RadFormDecorator.FindAndDecorateControls(Control parent) +630
   Telerik.Web.UI.RadFormDecorator.FindAndDecorateControls(Control parent) +630
   Telerik.Web.UI.RadFormDecorator.FindAndDecorateControls(Control parent) +630
   Telerik.Web.UI.RadFormDecorator.FindAndDecorateControls(Control parent) +630
   Telerik.Web.UI.RadFormDecorator.DecorateAspNetControls() +68
   Telerik.Web.UI.RadFormDecorator.ControlPreRender() +834
   Telerik.Web.UI.RadWebControl.OnPreRender(EventArgs e) +47
   System.Web.UI.Control.PreRenderRecursiveInternal() +80
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +842

 
I have tested a lot of scenarios with no success. RadGrids are both initialized programmatically (ItemCommand, ItemCreated, PreRender, NeedDataSource for NHibernate list).

After testing, exception raise when system tries to render manual columns (GridDateTimeColumn, GridBoundColumn) as  AutoGenerateColumns="False". If i remove manual columns, expand/collapse is working.

[Eyup]

Hello Davy,

For a practical implementation of hierarchical grid structure, please check out the following demos:
  - Standard Hierarchy
http://demos.telerik.com/aspnet-ajax/grid/examples/hierarchy/declarativerelations/defaultcs.aspx
  - Programmatic Hierarchy
http://demos.telerik.com/aspnet-ajax/grid/examples/hierarchy/autogeneratedhierarchy/defaultcs.aspx
  - Hierarchy with Templates
http://demos.telerik.com/aspnet-ajax/grid/examples/hierarchy/nestedviewtemplate/defaultcs.aspx
  - Template relations
http://demos.telerik.com/aspnet-ajax/grid/examples/hierarchy/nestedviewtemplatedeclarativerelations/defaultcs.aspx
  - Master / Detail grids
http://demos.telerik.com/aspnet-ajax/grid/examples/programming/selectedvalue/defaultcs.aspx

and choose the approach most suitable to your specific requirements.

If you are creating your grid programmatically, please note that RadGrid does not support mixing declarative grid columns with grid columns added dynamically at runtime as stated in this topic:
http://www.telerik.com/help/aspnet-ajax/grid-programmatic-creation.html#Section4

I hope this will prove helpful.

Kind regards,
Eyup
the Telerik team