C# Const field in abstract class

Question

I'm having trouble declaring a const field in an abstract class. Why is this?

edit

I should have clarified. My problem is that my child classes can't see the const field:

protected const string Prefix = "dynfrm_";

If I remove the const keyword, I can get to it from a grandchild class.

Given which answer directed you to the solution, you should have shown quite a bit more code. If we had actually seen your code, it would have been clear. — Dustin Campbell
– Dustin Campbell, Commented Jun 25, 2009 at 2:12

davmos · Accepted Answer · 2016-02-17 11:41:02Z

4

public abstract class Class1 { protected const string Prefix = "dynfrm_"; } public class Class2 : Class1 { public void GetConst() { Console.WriteLine(Prefix); } }

edited Feb 17, 2016 at 11:41

davmos

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answered Jun 25, 2009 at 2:09

Rony

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Comments

davmos · Accepted Answer · 2016-02-17 11:41:43Z

3

Here you go...

abstract class MyBase { protected const int X = 10; } class Derived : MyBase { Derived() { Console.WriteLine(MyBase.X); } }

edited Feb 17, 2016 at 11:41

davmos

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answered Jun 25, 2009 at 2:03

Gishu

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2 Comments

Ronnie Overby Over a year ago

MyBase is just base in c#. Besides, base.myConstFiled isn't working for me.

Timothy Carter Over a year ago

base is a c# keyword for the base class of the current class. MyBase is what Gishu declared as the abstract class in his sample code.

Dustin Campbell · Accepted Answer · 2009-06-25 02:08:21Z

Seems to work fine:

public abstract class Class1 { protected const int Field1 = 1; } public class Class2 : Class1 { public int M1() { return Field1; } }

I'm using Visual Studio 2008 SP1, and I see the protected const in IntelliSense from a descendant and it compiles as expected.

Tetraneutron · Accepted Answer · 2009-06-25 02:06:34Z

Did you make your constant at least protected? if it's private it won't be accessible by child classes just as it wouldn't if it wasn't an abstract class.

Edit: I see you posted an example - and did specify it as protected, which works for me. Got a description of what happens? Doesn't compile? run time error?

If a class is defined as abstact then it can never be initialized. Wouldn't this stop the compiler from initializing a const, which is inherently static?

KevDog · Accepted Answer · 2009-06-25 02:05:18Z

0

As long as you initialize it in the declaration, there shouldn't be an issue. What is the error message you are receiving?

answered Jun 25, 2009 at 2:05

KevDog

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2 Comments

Ronnie Overby Over a year ago

Error message? That's brilliant! "cannot be accessed with an instance reference; qualify it with a type name instead." I did this and it works. I guess it treats it as static when you use the const keyword.

Ronnie Overby Over a year ago

I was trying to access using this.Field.

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