Constant vs Readonly in C#

Answer»

The const in C# is faster than readonly, but the performance of const is not better than readonly.

A value with const KEYWORD cannot change throughout the LIFE of a program.

A const variable cannot be reassigned.

A value with Readonly keyword whose value can be initialized during runtime, unlike const.

Let us now see the DIFFERENCE:

Basis	Const	Readonly
Local Variable	Can be applied to local variables.	Cannot be applied to local variables
Memory	Memory is not allocated.	Dynamic memory is allocated for readonly fields.
Static	Const are by-default static	To make it class member, INCLUDE static keyword before readonly
Ref or out	We cannot pass const field as ref or out parameter	The readonly field can be passed as ref or out parameters in the constructor context.
Faster	Faster than readonly.	Readonly isn’t faster.
Performance	Performance isn’t better than readonly.	Performance is better than const.

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