Static class with static properties

Question

I'm trying to collect all string declarations in my app in a single class, so that they are easy to modify project-wide. I can create a Strings class like so:

public static class Strings
{
    public static readonly string Title = "App Title";
}

or like so:

public static class Strings
{
    public const string Title = "App Title";
}

The class should be static and all the properties constant. What difference does it make whether the properties of Strings have the static readonly or the const keywords in them?

`const` *implies* `static`, but the language won't allow you to use both keywords at the same time. — Lucas Trzesniewski, May 30 '15 at 11:16
Perhaps the biggest difference is that `const` would compile, while `static const` wouldn't. Did you mean `static readonly`? — Sergey Kalinichenko, May 30 '15 at 11:17
Thanks, I did not know it would not compile. Visual Studio did not indicate any errors until I actually tried to build. — transporter_room_3, May 30 '15 at 11:26
You might want to look into using a resource strings file (.resx), particularly if there is a possible future need for localisation. — Stephen Kennedy, May 30 '15 at 11:34

Yuval Itzchakov · Accepted Answer · 2015-05-30T11:30:28.383

You can look at the difference via a simple example:

void Main()
{
    var f = F.Foo;
    var b = F.Bar;
}

public class F
{
    public const string Foo = "F";
    public static readonly string Bar = "B";
}

Will yield the following IL:

IL_0001:  ldstr       "F"
IL_0006:  stloc.0     // f
IL_0007:  ldsfld      UserQuery+F.Bar
IL_000C:  stloc.1     // b
IL_000D:  ret

The const value of Foo is "baked" at compile to the call site, that is why you see a ldstr of the value "F" itself, while a static field emits a ldsfld, which loads the field at runtime, and then assigned it to the local variable b.

Making a field both static and const is a compile time error. Both const and static are defined on the type, not the instance. More so, a static field can be set at run-time, while const must be known at compile-time.

If you want to set a bunch of constant values that won't change at run time, going with a const should be fine. But you have to remember, that if you change a const value, it isn't enough to compile the source holding the consts, you'll have to re-compile anyone who consumes that const as well.

Static class with static properties

1 Answers1