Input string was not in a correct format

based on the error message, it possible that the value in e.Row.Cells[0].Text could be null or empty or not a valid number string. I suggest to use int.Tryparse method, see below as an example.

int number;

         bool result = Int32.TryParse(e.Row.Cells[0].Text, out number);
		
		
		if (result) {
			Console.WriteLine("aiyeee baaa");
		}
		else {
			Console.WriteLine("booo");	
		}