Your problem is that you don't initialize marks
. In the constructor you declare a local variable called marks
, but so your global one stays null. Change your constructor like this:
public TicTacModel()
{
red = {{false, false, false},
{false, false, false},
{false, false, false}};
marks = {{" ", " ", " "},
{" ", " ", " "},
{" ", " ", " "}};
}