Using array initializer '{}' multiple times for the same variable doesn't compile

Question

I am trying to compile following code in C#:

String[] words = {"Hello", "Worlds"};
words = {"Foo", "Bar"};

And I am getting compilation errors like:

Error 1 Invalid expression term '{'
Error 2 ; expected
Error 3 Invalid expression term ','

On the other hand if I try

String[] words = { "Hello", "Worlds" };
words = new String[] {"Foo", "Bar"};

It compiles fine. As per MSDN,

int[] a = {0, 2, 4, 6, 8};

it is simply a shorthand for an equivalent array creation expression:

int[] a = new int[] {0, 2, 4, 6, 8};

Why doesn't the first code sample compile?

Answer 1

Correct, the short initializer syntax is only allowed in a declaration. Not in a normal statement.

String[] words = new string[]{ "Hello", "Worlds" }; // full form
String[] words = { "Hello", "Worlds" };  // short hand, special rule
words = {"Foo", "Bar"};                  // not allowed
words = new String[] {"Foo", "Bar"};     // allowed, full form again

The short hand notation is only allowed when it used as (rhs) part of a declaration.

Answer 2

C# spec 12.6 Array initializers

In a field or variable declaration, the array type is the type of the field or variable being declared. When an array initializer is used in a field or variable declaration, such as: int[] a = {0, 2, 4, 6, 8}; it is simply shorthand for an equivalent array creation expression: int[] a = new int[] {0, 2, 4, 6, 8};

String[] words = { "Hello", "Worlds" };

is a declaration but

words = {"Foo", "Bar"};

is not.