64bit Enums? C#

Is it possible to get an enum to hold 64bit values? I wrote the code below and got this compile error message.

enum EnumTest { a = 0x100000000 };

error CS0266: Cannot implicitly convert type 'long' to 'int'. An explicit conversion exists (are 开发者_Go百科you missing a cast?)

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Yes, you need to "derive" it from long.

public enum MyEnum : long
{
}