Author: ytianle

`const` vs `static readonly`⚓︎

`const`⚓︎

In C#, const declares a compile-time constant whose value is baked into callers. A const must be initialized at its declaration with a constant expression.

Allowed const types are numeric types, char, bool, string, enum, and null (for reference types).

Here are some examples about what can be assigned to a const:

literals (10, "Hello", true)
other const values
simple compile-time expressions (1 + 2, 3 * 4)
compile-time constants from the language (Math.PI, DayOfWeek.Monday)

public class Example
{
    public const int MyConst = 10;  // assigned at declaration, cannot be changed after compilation
    public void PrintConst() => Console.WriteLine(MyConst);
}

`static`⚓︎

In C#, static is a keyword used to declare a member that belongs to the type itself rather than to any specific instance of the type. A static member can be accessed without creating an instance of the class.

public class Example
{
    public static int MyStaticValue = 20; // belongs to the class, can be accessed without an instance
}
public class Program
{
    public static void Main()
    {
        Console.WriteLine(Example.MyStaticValue); // Output: 20
    }
}

`readonly`⚓︎

In C#, readonly is a keyword used to declare a field that can only be assigned a value during its declaration or within a constructor of the same class. A readonly field cannot be modified after the constructor has finished executing.

public class Example
{
    public readonly int MyReadonlyValue = 30; // can be assigned at declaration

    public Example(int value)
    {
        MyReadonlyValue = value; // can be assigned in constructor
    }
}