What is a “static” class?

Question

In C# what is the difference between:

public static class ClassName {}

And:

public class ClassName {}

Answer 1

Static class can contain static members only.

Static member can be used without instantiating a class first.

Answer 2

All methods/properties in a static class must be static, whereas a 'normal' class can contain a mix of instance and static methods.

Answer 3

You can't instantiate (create objects of) a static class. And it can only contain static members.

Example: System.Math

Answer 4

A static class cannot be instantiated, and can contain only static members. Hence, the calls for a static class are as: MyStaticClass.MyMethod(...) or MyStaticClass.MyConstant.

A non static class can be instantiated and may contain non-static members (instance constructors, destructor, indexers). A non-static member of a non-static class is callable only through an object:

MyNonStaticClass x = new MyNonStaticClass(...);
x.MyNonStaticMethod(...);

Answer 5

A static class also can not be inherited from, whereas a non-static class with static members can be inherited from.

Answer 6

public static class ClassName {}

A static class is just like a global variable: you can use it anywhere in your code without instantiating them. For example: ClassName. After the dot operator, you can use any property or function of it.

 public class ClassName {}

But if you have non-static class then you need to create an instance of this class. For example:

 ClassName classNameObject = new ClassName();