What is difference between const & readonly keywords in C#?
Dung Do Tien
Oct 25 2021
116
Hello, I see my project in my company, someone usually write code as below:
private const int _timeInterval = 100;
private const int _timeFixedDefault = 150;
private readonly IMemberBoFE _memberBoFE;
private readonly UserManager<MemberAppUser> _userManager;
private readonly SignInManager<MemberAppUser> _signInManager;
public AccountController(IMemberBoFE memberBoFE, SignInManager<MemberAppUser> signInManager, UserManager<MemberAppUser> userManager)
{
_memberBoFE = memberBoFE;
_signInManager = signInManager;
_userManager = userManager;
}
It's really difficult to understand some variables using keyword const and some other use readonly.
Anyone can explain What is difference between const & readonly keywords in C#? And C# required to use them?
Thanks for any explanation.
Have 2 answer(s) found.
-
A1
Armin Habibi Oct 25 2021
Const
- It is mandatory to initialize the variable at the time of its declaration. But value must be fixed not get from dynamic, ex: 1,2, 4.65, "Hello world".
- It defaults to a static
- It is usually used for a variable value type.
- Variable can not change the value after it's declared.Readonly
- The read-only variable’s value cannot be modified once after its initialization. (after object instance)
- Readonly is usually used to create an instance for a class, object. -
A0
An Pham Truong Oct 25 2021
- Const is only used for value type variables such as int, string, bool, datetime....
- Readonly can use for all value types and reference types.
- Const doesn't allow change value after declare.
- Readyonly not allow change after class is instanced.
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