Question

I a sample C# console application to display a bug I am experiencing:

class Program
{
    public enum Days { Sat = 1, Sun, Mon, Tue, Wed, Thu, Fri };

    static void Main(string[] args)
    {
        AddWhere("a", DateTime.Now);
        AddWhere("a", 0);
        AddWhere("a", 2);
        AddWhere("a", 3);
        AddWhere("a", "4");
        AddWhere("a", Days.Sun);
        AddWhere("a", Days.Fri);
        AddWhere("a", 1);
        AddWhere("a", (int)Days.Sat);
        Console.Read();
    }

    public static void AddWhere(string columnName, Days cd)
    {
        Console.WriteLine("enum fired");
    }


    public static void AddWhere(string columnName, object Val)
    {
        Console.WriteLine("object fired");
    }
}

the output I get is this:

object fired
enum fired
object fired
object fired
object fired
enum fired
enum fired
object fired
object fired

Why does the enum method fire when 0 is passed in?

Answer 1

The special case of 0 is covered in section 1.10 of the C# language specification.

In order for the default value of an enum type to be easily available, the literal 0 implicitly converts to any enum type

This implicit conversion is causing overload resolution to pick the enum overload over the object one.