Static Using Statement

The feature allows all the accessible static members of a type to be imported, making them available without qualification in subsequent code:

using static System.Console;
using static System.Math;
using static System.DayOfWeek;
class Program
{
    static void Main()
    {
        WriteLine(Sqrt(3*3 + 4*4)); 
        WriteLine(Friday - Monday); 
    }
}

This is great for when you have a set of functions related to a certain domain that you use all the time. System.Math would be a common example of that. It also lets you directly specify the individual named values of an enum type, like the System.DayOfWeek members above.