DataGrid Performance changes within different Panels

Hi,

I have a DataGrid with few thousand rows within the DockPanel. There are also buttons at the bottom of the Dockpanel.  But because my DataGrid is within the DockPanel the buttons are never visible.  So I replaced the DockPanel with StackPanel and thought to fill the remaining space inside the StackPanel with DataGrid.  So that user can see buttons at the bottom.  But when I did that the View or UserControl takes a way too long to load.  This is not the case with DockPanel. 

I can't think of any way out of this.  Can anyone suggest some solution please ?