Difference between readonly and const keyword in C#
readonly keyword
readonly keyword is used to define a variable which can be assigned once after declaration either during declaration or in constructor. const keyword is used to define a constant to be used in the program. Following is the valid usage of a readonly and const keywords in C#.
Example
Live Demo
using System.IO;
using System;
public class Program {
public const int VALUE = 10;
public readonly int value1;
Program(int value){
value1 = value;
}
public static void Main() {
Console.WriteLine(VALUE);
Program p1 = new Program(11);
Console.WriteLine(p1.value1);
}
}Output
10
11
Following are some of the important differences between readonly and const keywords.
| Sr. No. | Key | readonly keyword | const keyword |
|---|
| 1 | Purpose | readonly keyword is used to create a readonly fields. | const keyword is used to create constant fields. |
| 2 | Type | readonly is a constant defined at runtime. | const is used to create a constant at compile time. |
| 3 | Change | readonly field value can be changed after declaration. | const field value cannot be changed after declaration. |
| 4 | Method | readonly fields cannot be defined within a method. | const fields can be declared within a method. |
| 5 | Value assignment | readonly variables are declared as instance variable and assigned values in constructor. | const fields are to be assigned at the time of declaration. |
Published on 15-Apr-2020 10:12:53
