What is the purpose of the static keyword in C#?

In C#, the static keyword has several uses:

1. Static class: Defined using the static keyword, a static class can only contain static members (methods, properties, fields, etc.), cannot be instantiated, and cannot inherit from other classes. Static classes are typically used to provide a set of related utility methods or global access points.
2. Static members: defined using the static keyword, they belong to the class rather than instances and can be accessed directly through the class name without the need to create an instance. Only one copy of a static member exists in memory, preventing the need for repetitive memory allocation when creating multiple instances.
3. Static constructor: A static constructor is defined using the static keyword. It is automatically called before the class is first used to initialize static members. Static constructors have no parameters and cannot be directly called, only automatically called by the CLR at runtime.
4. Static properties: Defined using the static keyword, these properties belong to the class rather than instances and can be accessed directly through the class name without needing to create an instance. They provide class-level access control and computing logic.
5. Static field: A static field is defined using the keyword “static”. Static fields belong to the class itself rather than an instance, and can be accessed directly through the class name without needing to create an instance of the class. There is only one copy of a static field in memory, so it is not duplicated for each instance created. Static fields can be used to store class-level state information.

In general, the static keyword is used to indicate that a member or class belongs to the class level rather than the instance level, and can be accessed directly through the class name.