static void Main()
{
var names = new MyChildClass();
names[DataColumns.Grades, 1] = 'S';
names[DataColumns.NameList, 9] = "W.S";
}
static void Main_01(string[] args)
{
Console.WriteLine("Hello World!");
MyBaseClass b = new MyBaseClass(); //base
Console.WriteLine(b.sum(3, 2));
MyBaseClass bc = new MyChildClass();//Child
Console.WriteLine(bc.sum(5, 2));
MyChildClass c = new MyChildClass(); //child
Console.WriteLine(c.sum(30, 2));
}