method with params

Question

I wrote this method:

static long Sum(params int[] numbers)
{
    long result = default(int);

    for (int i = 0; i < numbers.Length; i++)
        result += numbers[i];

    return result;
}

I invoked method like this:

Console.WriteLine(Sum(5, 1, 4, 10));
Console.WriteLine(Sum());  // this should be an error
Console.WriteLine(Sum(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15));

I want the compiler to shows an error when I call the method without any parameters (like Sum()). How can I do this?

Answer 1

Extract first parameter out of params to make it mandatory:

static long Sum(int firstSummand, params int[] numbers)

Answer 2

You could write

 static long Sum(int number1, params int[] numbers)
 {
     long result = number1;
     ....
 }

But then you would lose this option:

 int[] data = { 1, 2, 3 };
 long total = Sum(data);   // Error, but Sum(0, data) will work.