CODEWITHSUNDEEP
c#static-initializer
Alex
Alex

Reputation: 77329

Initialization Order of Static Fields in Static Class

given the following code:

public static class Helpers
{
   private static Char[] myChars = new Char[] {'a', 'b'};

   private static Int32 myCharsSize = myChars.Length;
}

Is it guaranteed that myChars will be initialized before I use its length to assign to myCharsSize?

Upvotes: 62

Views: 8200

Answers (3)

Andrew Hare
Andrew Hare

Reputation: 351476

Yes, they will, please see clause 15.5.6.2 of the C# specification:

The static field variable initializers of a class correspond to a sequence of assignments that are executed in the textual order in which they appear in the class declaration (§15.5.6.1). Within a partial class, the meaning of "textual order" is specified by §15.5.6.1. If a static constructor (§15.12) exists in the class, execution of the static field initializers occurs immediately prior to executing that static constructor. Otherwise, the static field initializers are executed at an implementation-dependent time prior to the first use of a static field of that class.

That being said I think it would be better to do the initialization inside a static type initializer (static constructor).

Upvotes: 74

Marc Gravell
Marc Gravell

Reputation: 1062620

Hmm... I'm surprised that compiles (it does, I checked). I'm not aware of any guarantee that would make this safe. Use a static constructor...

Edit: I accept (see better answer above) that it will work; but my idea with code is to keep it as simple and obvious as possible. If it isn't obvious that it will work (and it can't be if you have to ask), then don't write it that way...

In particular, problems with relying on field order:

  • it can break if you move code around (which I often do)
  • it can break if you split the code into partial classes

My advice remains: use a static constructor for this scenario.

Upvotes: 18

Jon Seigel
Jon Seigel

Reputation: 12401

At first glance, I wouldn't be sure, and I had to try this out to see if it even compiled.

Given that, I would initialize the value in a static constructor.

Upvotes: 0

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