title: Open a new window in WPF using MVVM
body: <p>I am new to MVVM .I have a window Demo.xaml which has menu, under menu i have sub menus.I want to open sub menu window i.e Test.Xaml on the click of submenu using MVVM approach.
  I made an object of Test Window but it didn't showed "Show" property.
  I also tried by using Delegate Commands but i failed.
  How can I achieve this?</p>