Is there a more elegant way to add nullable ints?

I need to add numerous variables of type nullable int. I used the null coalescing operator to get it down to one variable per line, but I have a feeling there is a more concise way to do this, e.g. can't I chain these statements together somehow, I've seen that before in other code.

using System;

namespace TestNullInts
{
    class Program
    {
        static void Main(string[] args)
        {
            int? sum1 = 1;
            int? sum2 = null;
            int? sum3 = 3;

            //int total = sum1 + sum2 + sum3;
            //int total = sum1.Value + sum2.Value + sum3.Value;

            int total = 0;
            total = total + sum1 ?? total;
            total = total + sum2 ?? total;
            total = total + sum3 ?? total;

            Console.WriteLine(total);
            Console.ReadLine();
        }
    }
}

var nums = new int?[] {1, null, 3};
var total = nums.Sum();

This relies on the IEnumerable<Nullable<Int32>>overload of the Enumerable.Sum Method, which behaves as you would expect.

If you have a default-value that is not equal to zero, you can do:

var total = nums.Sum(i => i.GetValueOrDefault(myDefaultValue));

or the shorthand:

var total = nums.Sum(i => i ?? myDefaultValue);

total += sum1.GetValueOrDefault();

etc.