Question

So i am in some window2 from this window I tried get frame defined in MainWindow.xaml
by creating a object of Mainwindow and tried to Navigate to a page but program giving ” null reference exception unhandeled by user code”

I used:

 public Window2()
  {
   }

 myfunction()
 {
 MainWindow rootwindow = new MainWindow();
  rootwindow.myframe.Navigate( new Page1());
  }

Answer 1

This is not how you get the frame from another window, you are just creating a new window and try to access something which is not loaded yet as the window you just created has not even been shown yet.

You need a reference to your window, which you could get from Application.Current.MainWindow if you set that accordingly beforehand (e.g. in the App class). Or you could pass a reference to the main window in the constructor of your second window.