private void Button_Click_Decimal(object sender, RoutedEventArgs e)
 {
     if (!InputBox.Text.Contains("."))
     {
         CalcController.AddTextToInput(".");
     }
 }
 private void Button_Click_Negate(object sender, RoutedEventArgs e)
 {
     // Check if negative exists, if so, remove it, else, add it.
     if (InputBox.Text.Contains("-"))
     {
         InputBox.Text = InputBox.Text.TrimStart('-');
     }
     else
     {
         CalcController.AddTextToInput("-", 0);
     }
 }
 private void Button_Click_6(object sender, RoutedEventArgs e)
 {
     CalcController.AddTextToInput("6");
 }