c# - How to solve the event can only occur on right hand of += or -= -

i working on c# on wpf application.i have written following code

public partial class mainwindow : window {     public mainwindow()     {         radiobutton daw;         initializecomponent();          if (qoneone.checked == true)         {             messagebox.show("correct");          }     } 

a error occurs says

event qoneone.checked can appear on left hand side of += or -=

you have check property qoneone.ischecked == true.

ischecked property can read or write or change current state of radiobutton.

checked event, can attach handler trough += can when radiobutton state change.