WPF - C# - open parent window only once -

i´m programming simple thing in c# , wpf. have mainwindow button. if trigger button opens secon window:

private void btnf4_click(object sender, routedeventargs e) {      secondwindow second = new secondwindow();      second.show(); } 

naturally if trigger button 3 or 4 times, have 3 or 4 windows open. don´t want use showdialog(), want open second window once. mean if trigger button , window open, should nothing happen.

thank you!

make second instance variable parent window class , create new window if hasn't been created.

of course need make sure null instance variable when second window closed.

public class parentwindow ... {     private secondwindow m_secondwindow = null;      ....      private void btnf4_click(object sender, routedeventargs e)     {         if (m_secondwindow == null)         {             m_secondwindow = new secondwindow();             m_secondwindow.closed += secondwindowclosed;             m_secondwindow.show();         }     }       public void secondwindowclosed(object sender, system.eventargs e)     {         m_secondwindow = null;     } }     

this might shortened following:

public class parentwindow ... {     private secondwindow m_secondwindow = null;      ....      private void btnf4_click(object sender, routedeventargs e)     {         if (m_secondwindow == null)         {             m_secondwindow = new secondwindow();         }          m_secondwindow.show();                 } }     

however, i'm never sure whether can "reopen" window closed before. if need initialize window on upon reopening, use first code. if can live window starting showing previous content, use second.