What is the difference between constant and read only in c#

What is the difference between constant and read only in c#

Constants are declared at compile time using the const keyword and must be initialized when they are declared

Constants value cannot be changed at runtime.

public class CodeViewClass

{

    public const int GST18 = 18;

}

A readonly is similar like a constant behaviour with an unchanging value.

But the main difference is that it can be initialized at runtime in a constructor.

public class CoderSampleClass

{

    // here readonly fiels is declared and asigned value

    public readonly int GST18 = 18;

    //OR

    // here readonly fiels is declared

    public readonly int GST28;

    public CoderSampleClass()

    {

        // here initializeing vaule in readonly fiels

        GST28 = 28;

    }

}

CONST

• The value of constant is evaluated at compile time
• You must assign value const field at time of declaration
• In C# Const are by default static.
• The value is same for all objects and cannot be changes
• No Memory Allocated Because const value is embedded in IL code itself after compilation.
• Const variable can not be passed as ref or out parameter

ReadOnly

• The value is evaluated at run time.
• You can assign value readonly field at the time of declaration
• The value can be change by initializing in the constructor.
• Dynamic memory allocated for readonly fields
• You can pass readonly field as ref or out parameters in the constructor context.