switch(place)
{
case 1:
string a = "X";
break;
case 2:
string b = "X";
break;
case 3:
string c = "X";
break;
case 4:
string d = "X";
break;
case 5:
string e = "X";
break;
case 6:
string f = "X";
break;
case 7:
string g = "X";
break;
case 8:
string h = "X";
break;
case 9:
string i = "X";
break;
}
With out more code it is hard to say what is happening and hard to duplicate the error. What jumps out at me is the string a = "X";. I wonder if you are trying to redefine the variables here?
Try defining the variables out side of the switch and make the case statements just a = "X"; and see what happens.