Can we use a field before declaring in C#?

Question

Hello,

I expect a compiler error because I didn't declare Y before using it.

Can we use a field before declaring in C#?

    class Foo
    {
         public static int X = Y;    // 0 -> I Expect a compiler error here!
         public static int Y = 3;    // 3
    }

Answer 1

Hi @Shervan360 ,

In C#, fields are initialized in the order they appear in the class. Therefore, when the compiler encounters public static int X = Y;, the field Y has not been initialized yet, but it does exist with its default value, which is 0 for an int. This is why the value 0 is assigned to X and no compiler error occurs.

The initialization process works as follows:

1. When X is being initialized, the field Y has been declared but not yet assigned the value 3. It holds the default value for its type, which is 0 in this case.
2. Therefore, X gets the value of Y, which is 0.
3. Then Y gets initialized with the value 3.

Best Regards.

Jiachen Li

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