Create a type alias (typedef)

The full name of the class also becomes very long, and sometimes it is a waste of time.
Today, I occasionally flipped through the book and found that using can actually define the class or namespace alias.
For example:
Using cryptns = realestate. Common. crypto;
Using cryptmgt = realestate. Common. crypto. cryptomanagement;
Class AA
{
Private void AAA ()
{
// The two are the same implementations.
Cryptns. cryptomanagement Mgt = new realestate. Common. crypto. cryptomanagement ();
Cryptmgt mgt1 = new realestate. Common. crypto. cryptomanagement ();
}
}