const variables

[ata]

Hi,
consider the following class:

public class MyClass
{
public const String TableName = "myTable";

public const String Relation1 = TableName + "_WhateverEntity";
}

I would like to know whether the Relation1 constant calculated every
time the class is instantiated. Is the variable being initialized at
the compile-time or on the run-time?

Thanks.

 

[Bob Powell [MVP]]

Consts are, by definition, constant so it's the compiler that does the work
here.


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[Alberto Poblacion]

consider the following class:

public class MyClass
{
public const String TableName = "myTable";

public const String Relation1 = TableName + "_WhateverEntity";
}

I would like to know whether the Relation1 constant calculated every
time the class is instantiated. Is the variable being initialized at
the compile-time or on the run-time?

You can answer questions like this by means of the intermediate language
disassembler, ILDASM.EXE. Just write your code and compile it into an .exe.
Then open a Visual Studio command prompt and start ILDASM on your assembly:
ILDASM myprogram.exe. You will see a tree on screen where you class
contains, among other things, your "public static literal string" constants.
Double-click on Relation1 and you will see its corresponding MSIL code:

..field public static literal string Relation1 = "myTable_WhateverEntity"

Which shows you that the compiler has indeed performed the operation.

 

[ata]

You can answer questions like this by means of the intermediate language
disassembler, ILDASM.EXE. Just write your code and compile it into an .exe.
Then open a Visual Studio command prompt and start ILDASM on your assembly:
ILDASM myprogram.exe. You will see a tree on screen where you class
contains, among other things, your "public static literal string" constants.
Double-click on Relation1 and you will see its corresponding MSIL code:

.field public static literal string Relation1 = "myTable_WhateverEntity"

Which shows you that the compiler has indeed performed the operation.

Thanks. Does the same concept apply to the C++ programs?

 

[Ben Voigt [C++ MVP]]

While the conclusion is correct, the logic used to arrive at it is
false. Not all implementations of a "constant" are compile-time. Read-only
variables with initializers are constant too, but those are
run-time constructs. Being "constant" does not actually imply
compile-time initialization.

Actually in C# it does. A read-only variable would be marked "readonly"
("initonly" in MSIL), not "const".

All "const" variables are substituted by the compiler.