Difference Between Constant and ReadOnly in C# | CSharp Interview Questions & Answers

[@questpondvideos]

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[@zerosandones7547]

Constants: Constants based on "consts": - const fields are called compile-time constants - an absolute constant - the value of a const variable is set during the declaration itself - consts variables SHOULD have a value when declared - the const's value is stored in the IL code itself Constants based on "readonly": - the modifier readonly creates fields, which values cannot be changed once they are assigned. - don't need to define a value during the declaration itself (a readonly field cannot be assigned to (except in a constructor or init-only setter of the type in which the field is defined or a variable initializer)) - readonly fields are called run-time constants - their values cannot be changed after assignment - this process(value assignment) happens during the execution of the program (in runtime)

[@klocugh12]

You didn't mention one thing about const: Compiler actually writes literal value of const as is when compiling. So there is no variable in memory, just a literal 100 number. It is important when you use it in other assemblies. When you modify it where it's defined, other assemblies will still hold value it had when it was compiled, so they have to be recompiled again!

[@expertreviews1112]

absolutely fantastic video. goodness me such good explanation. Be Blessed

[@dnskk]

sir const are implicitly static so u need not to put static in front of them

[@RohanShirodkar29]

Thanks for sharing this informatational video

[@faisalraufpitafi1396]

sir Aslam o alikum I am from Karachi Pakistan I like your teaching way Mashallah Mashallah you are perfect teacher and I will share your videos with my friends because I want they should learn .

[@HikeThePlanets]

Thanks so much for explaining that so simply and thoroughly.

[@nocultist7050]

This is a hidden gem of a channel.

[@mradosovic]

Very nice explanation with a good example.

[@harshsaxena05]

excellent explanation thank you.

[@pcm0it]

The static modifier is not allowed in a constant declaration.

[@olglez9230]

Nice one. Very clearly explained with a good example. This may come up on an interview open day!

[@amolshinde7832]

Very good explanation, thanks

Very helpful. Thank you. Never really understood the point of readonly until now.

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[@venkateshpillay3213]

Great sir 👌 Thank you

[@marklitvin9291]

Very well explained. Thank you!

[@aks-tech-1]

I have one suggestion here. You can brief the topic and then explain the programming. You are good in all the way. I am your paid user

[@Shakti_Singh_Om]

Important point here is that constants are by default static. You can use static keyword with Readonly and not with constants.

[@sery152]

Can you explain the logic of static inline with const and readonly, they have contradictins...

[@rjshukla_vlogs]

Hello Sir ji .. Its really nice example but i have 1 question here that we can't have static and const simultaneously ?? it is saying that you cant have static with the const ? Could you please let me know how this happens in your example ?? Thanks you so much for your help :)

[@AachaLagaNa]

Seems that code is written in text editor not in any fiddler or vs ide.

[@rjshukla_vlogs]

But while. Running the application how it is showing the correct output.

[@tusharghude15]

watch carefully he changed it (at 05:48 u can see suddenly public and static disappeared) ur rgt constants cannot be declared as static coz they are implicitly static u always use const like classname.const_var

[@vatansoni6439]

+tushar ghude good

[@dineshkumarachari8757]

@@tusharghude15 correct! but he not mention that point is important point.

[@kavithan1987]

Instead of read-only we can use integer right..is their any difference in memory allocation

[@naterdanger3919]

Forgive me if this was asked already, but is it necessary to label it constant to begin with? Why/When would we need to do such a thing?

[@jvsnyc]

It is to protect you against goofy mistakes by yourself or others on your team. If something is logically a compile-time constant (or even readonly) if you try to change it later by mistake you can't. There are also optimizations that can be applied to values known not to change, but that is secondary.

[@rohitjoshi3240]

You declare the static Constructor and used the access modifier, which prone to error.

[@saurabhmahal1354]

Great way to tell the difference ...thanks

[@rajarajanseeman6758]

Still wondering how would you be able to mark as static in const variable? I see the below error Error 1 The constant 'xxx.Program.myproconst' cannot be marked static

[@AachaLagaNa]

Seems that code is written in text editor not in any fiddler or vs ide.

[@jvsnyc]

If it is not clear to anyone, that's right, it can't. Doubly confusing for C++ programmers coming over to C# because in C++ const has a different meaning and does not automatically imply static. In C# it appears const implies static and you can't say both just for fun or to be more clear. In C++ the same thing would be static const, because if you said just const you would get one for each object instance. C# has a readonly keyword that doesn't exist in C++.

[@sandeepadode1]

My question is why to read only?A constant is constant right be it at compile time or at run time.Does it have any impact on the program?please help.What exactly is the use of using anyone among them?

[@jvsnyc]

It is to protect you against goofy mistakes by yourself or others on your team. If something is logically a compile-time constant (or even readonly) if you try to change it later by mistake you can't. There are also optimizations that can be applied to values known not to change, but that is secondary.

[@manjeetnandal1]

Great sharing! Thanks....

[@pankajjha1914]

thnku sir.

[@PanikGrafik]

Dont forget that the value IS STILL HELD !!!

[@Albileon]

Really good, thanks.

[@ahmadezzat9031]

The const is by default static.

[@prateekbhardwaj9943]

nicely explained

[@ankitsinha007]

A static constructor does not have access modifier

[@zerosandones7547]

static constructor in IL code is cctor

[@MrJonnis13]

Thank you

[@yeshyuvi]

its good and thank u

[@smanputra]

great explanation and examples..

[@williamwang2047]

i think u said wrong, PI should be const, as it never changed......

[@codewithparveenyadav]

useful

[@semikolon4229]

thanks, very useful

[@hlch7774]

const no need to use static

[@lakshmisruthi1342]

I wish I watched this video before attending interview :/

[@wiepcorbier]

Stop the "you know" please.

[@naturebc]

This is one of those things that makes a language worse. More complex for no good reason at all.