Static class cannot be instantiated

Context: A static class can only contain static members and cannot be instantiated or inherited.

Declaration

public static class Utility
{
    public static int Add(int a, int b) => a + b;
    public static double Pi = 3.14159;
}

Usage

int sum = Utility.Add(5, 3);
Console.WriteLine(Utility.Pi);

Rules

• No instance constructors.
• Cannot use new to create objects.
• Cannot be used as a base class.
• All members must be static.

Common Examples

• Math (Sin, Cos, Sqrt)
• Console (WriteLine, ReadLine)
• Convert (ToInt32, ToDouble)

Static vs Non‑Static Class

Feature	Static Class	Non‑Static Class
Instantiation	No	Yes
Instance members	No	Yes
Inheritance	No	Yes
Constructor	Static only	Instance + static