static void Main(string[] args)
{
FromClass fromClass = new FromClass();
fromClass.exam();
SimpleLinq simpleLinq = new SimpleLinq();
simpleLinq.exam();
FromFrom fromFrom = new FromFrom();
fromFrom.exam();
GroupByClass groupByClass = new GroupByClass();
groupByClass.exam();
JoinClass joinClass = new JoinClass();
joinClass.exam();
}
