Why is this c# snippet legal?

Question

Silly question, but why does the following line compile?

int[] i = new int[] {1,};

As you can see, I haven't entered in the second element and left a comma there. Still compiles even though you would expect it not to.

Answer 1

I suppose because the ECMA 334 standard say:

array-initializer:
    { variable-initializer-list(opt) }
    { variable-initializer-list , }
variable-initializer-list:
    variable-initializer
    variable-initializer-list , variable-initializer
variable-initializer:
    expression
    array-initializer

As you can see, the trailing comma is allowed:

{ variable-initializer-list , }
                            ↑

---

P.S. for a good answer (even if this fact was already pointed by many users). :)

Trailing comma could be used to ease the implementation of automatic code generators (generators can avoid to test for last element in initializer, since it should be written without the trailing comma) and conditional array initialization with preprocessor directives.

Answer 2

This is syntax sugar. In particular, such record can be useful in code generation.

int[] i = new int[] {
    1,
    2,
    3,
};

Also, when you are writing like this, to add new line you need to add text only in single line.