How to find your application window/childwindow using TestStach.White

Try below code to find your application window/child windows by using TestStack.White framework -
Lets take NotePad as our application -

  //get the required window
  List windows = new List();            
  windows = Desktop.Instance.Windows(); 
  //Get all the windows on desktop            
  for (int i = 0; i < windows.Count; i++)
  {                
      string str = windows[i].Title;
      if (str.Contains("Notepad")) 
         //compare which window title is matching to your string
         {                    
         mainwindow = windows[i];
         //Log("mainwindow detected");
         break;                
         }
  }
  //pop out "Font" window from the notepad with the below keypress

  mainwindow.Keyboard.PressSpecialKey(KeyboardInput.SpecialKeys.ALT);            
  mainwindow.Keyboard.Enter("O");            
  mainwindow.Keyboard.Enter("F");

  //Find the Font window from the mainwindow (modal window)
  Window font = mainwindow.ModalWindow("Font");