在wpf中重复打开对话框时的性能问题

I have a launch dialog button which creates a view model of a window and bind it to the the window(it is having UI virutalization enabled). It takes only 1 second to launch the dialog at first click. But if I open the same dialog very frequently or back to back, it starts taking more time in populating the grid data source for next iteration. if I give some pause, then again open window, then it takes only approx 1 or 2 seconds.I have a launch dialog button which creates a v