Question

why this return 5,I’m curious about this the normal function have higher priority over with a default parameter one. can some body explain me this. thanks in advance

static void Main(string[] args)
{
        Console.WriteLine(add());

        Console.ReadLine();
}



public static int add(int x=4,int y=5)
{
        return x+y;
}

public static int add()
{

        return 5;

}

Answer 1

I think this can only be answered by looking at the C# language specification. Section 7.5.3.2 says that when determining a “Better” function member, if the optional arguments are not needed, you throw them out:

Optional parameters with no corresponding arguments are removed from
the parameter list

That effectively makes the two functions equivalent. It then has the following tie-breaker rule for when two functions are equivalent:

Otherwise if all parameters of MP have a corresponding argument
whereas default arguments need to be substituted for at least one
optional parameter in MQ then MP is better than MQ.

That would mean that the one without the default arguments would be the one called – just as you’re seeing in your code.