Static Class and Constructor

What is a static class?

When we use the static keyword before a class name, we specify that the class will only have static member variables and methods. Such classes cannot be instantiated as they don’t need to: they cannot have instance variables. Also, an important point to note is that such static classes are sealed by default, which means they cannot be inherited further.

This is because static classes have no behavior at all. There is no need to derive another class from a static class (we can create another static class).

Why do we need static classes?

As already written above, we need static classes when we know that our class will not have any behavior as such. Suppose we have a set of helper or utility methods which we would like to wrap together in a class. Since these methods are generic in nature, we can define them all inside a static class. Remember that helper or utility methods need to be called many times, and since they are generic in nature, there is no need to create instances. E.g., suppose that you need a method that parses an int to a string. This method would come in the category of a utility or helper method.

So using the static keyword will make your code a bit faster since no object creation is involved.
The main features of a static class are:

1. They only contain static members.
2. They cannot be instantiated.
3. They are sealed.
4. They cannot contain Instance Constructors (C# Programming Guide).

Static Constructor in C#

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