How Does C# Guarantee a Deterministic Order for Static Class Initialization?

Deterministic Order of Static Class Initialization in C#

The order of static class initialization in C# is clarified by the ECMA specification. This order ensures consistency in program behavior.

According to ECMA-334:

• When a static field initializer exists, it executes immediately before the corresponding static constructor.
• If there's no static constructor, initializers execute at an implementation-dependent time before using any static field of the class.
• Execution of a static constructor triggers when either an instance of the class is created or any static member is referenced.
• In classes with a Main method, the static constructor executes before entering the Main method.

In the given code sample:

1. Referencing A.X in Main triggers the initialization of A.X.
2. A.X initialization requires B.X, so it initiates B.X initialization.
3. B.X is assigned a default value of 7. Output: "B.X = 7."
4. Static B() is called, outputting "B.X = 0."
5. A.X is initialized as B.X 1, resulting in A.X = 1.
6. Static A() is called, outputting "A.X = 1."
7. Finally, Main prints "A = 1, B = 0."

The standard discourages observing static fields with variable initializers in their default state to maintain consistency.

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