c# - Need to get an equivalent item in list box when I input a number -

i'm new c# , i've been struggling program. im doing alias generator program. when input number in textbox (ex. 1-12) should equivalent item in listbox.

lblalias.content = lstbox1.items(convert.toint16)(txtmob.text)[0 - 1].tostring(); 

i'm not wpf programmer (i use winforms, sorry), like...

    private void button_click(object sender, routedeventargs e)     {         int month, day;         if (int.tryparse(txtmob.text, out month) && int.tryparse(txtdob.text, out day))         {             if(month >= 1 && month <= 12 && day >= 1 && day <=31)             {                 lblalias.content = ((listboxitem)lstbox1.items[month - 1]).content.tostring()                     + " " + ((listboxitem)lstbox2.items[day - 1]).content.tostring();             }             else             {                 messagebox.show("month must between 1 , 12, , day must between 1 , 31!");             }         }         else         {             messagebox.show("invalid month and/or day!");         }     }