C# - What is the Difference between Const and Readonly

Const:

      1.    Const can only be initialized at the time of declaration of the field.

      2.    Const values will evaluate at compile time only.

      3.    Const value can’t be changed these will be same at all the time.

      4.    This type of fields are required when one of the field values remains constant throughout the system like Pi will remain same in your Maths Class.

Read-only:

     1.    The value will be initialized either declaration time or the constructor of the class allowing you to pass the value at run time.

      2.    Read only values will evaluate at runtime only.

        

Example

public class Const_VS_Readonly { public const int I_CONST_VALUE = 2; public readonly int I_RO_VALUE; public Const_VS_Readonly() { I_RO_VALUE = 3; } }

Suppose if you want the value of the constant won't change use a const or if you have a constant that may change or when in doubt, use a readonly.  I hope it helps.