wpf - C#: Cast to Base -

i have datagrid column contains link. file gets opened on click

<datagridhyperlinkcolumn binding="{binding path=number}" >     <datagridhyperlinkcolumn.elementstyle>         <style>             <eventsetter event="hyperlink.click" handler="linkclicked"/>         </style>     </datagridhyperlinkcolumn.elementstyle> </datagridhyperlinkcolumn> 

i use method

public void linkclicked(object sender, routedeventargs e)  {     var vm = (basepartviewmodel<part>) datacontext;     vm.openfile(); } 

i use code in base viewmodel class.

but problem cast not work

(basepartviewmodel<part>) datacontext 

because every implementation different. instance

(basepartviewmodel<plug>) datacontext 

and plug derives part. how make work without implementing method in every derived viewmodel?

you factor out openfile method covariant interface , cast interface.

interface myinterface<out t> {     void openfile(); }  class plug : part { }   class part { }  class basepartviewmodel<t> : myinterface<t> {     public void openfile()     {         throw new notimplementedexception();     } }  class program {     static void main(string[] args)     {         basepartviewmodel<plug> derived = new basepartviewmodel<plug>();         myinterface<part> b = derived;         b.openfile();     } }