You can use this line of code:

int id = Convert.ToInt32(Request.QueryString["QOT_ID"]);

You can use this line of code:

int id = Convert.ToInt32(Request.QueryString["QOT_ID"]);

Or this if you want to do proper checking:

int id;
if (int.TryParse(Request.QueryString["QOT_ID"], out id)) {
    // Do something with the id variable
} else {
    // Do something when QOT_ID cannot be parsed into an int
}