C# Const: Immutable Constants Explained

In C#, the const keyword is used to declare a constant field or local variable. Its purpose is as follows:

1. The const keyword can be used to define an immutable constant. Once a constant is defined, its value cannot be changed.
2. Compile-time constants: Constants defined using the const keyword are resolved to their values during compilation, rather than being calculated at runtime. This can improve the performance of the program.
3. Avoid magic numbers: Using const constants can help avoid using magic numbers in code. By giving a meaningful name to constants, code readability and maintainability can be improved.
4. Symbolic constants: const constants can be used as symbolic constants so they can be easily updated in the code without having to search and modify every instance in the code if their values need to be changed.

It is important to note that const constants can only be constant expressions known at compile time, such as literals, other const constants, enum values, or operations that can be determined by the compiler. Constants cannot be defined using variables that are only determined at runtime.