Showing MultiPle UserControl in a Window as ChildWindows

I have developed a WPF ERP in which i have a single main window and rest windows i have crea开发者_开发知识库ted as UserControls... Currently I am displaying the user controls in a ContentFrame in the MainWindow but my problem is that i can only display a single user control in a WPF Content Frame and i cant create a Content Frame dynamically...

How can i overcome this...

I have opened the child window as

Stock s=new Stock(); //UserControll
mainGrid.Children.Add(s);