private static void EnterGrades(IBook Br)
{
var input = "";
Double Grade;
while (true)
{
Console.WriteLine("Enter Grades or q to quit");
input = Console.ReadLine();
if (input == "q")
{
break;
}
try
{
Grade = Convert.ToDouble(input);
Br.AddGrades(Grade);
}
catch (ArgumentException ex)
{ Console.WriteLine(ex.Message); }
catch (FormatException ex)
{ Console.WriteLine(ex.Message); }
}
}