Is there a more elegant way to add nullable ints?

Question

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 conc

Answer 1

Simplest, most elegant usage of LINQ:

var list = new List<Nullable<int>> { 1, 2, null, 3 };
var sum = list.Sum(s => s ?? 0);
Console.WriteLine(sum);

You need the coalesce AFAIK to make sure the result is not nullable.

Answer 2

If all numbers in the array are null I would expect the total to be null.

// E.g. 
int? added = null, updated = null, deleted = null; 
...
int? total = added + updated + deleted; // null i.e. nothing has been done.

Test Cases

Sum(new int?[] { null, null}).Dump(); // null   
Sum(new int?[] { 1, null}).Dump();    // 1
Sum(new int?[] { null, 2}).Dump();    // 2
Sum(new int?[] { 1, 2}).Dump();       // 3

Sample Implementation

int? Sum(int?[] numbers)
{
    int? total = null;

    for (int i = 0; i < numbers.Length; i++)
    {
        int? item = numbers[i];
        if (item != null)
        {
            if (total == null)
            {
                total = item;
            }
            else
            {
                total += item;
            }
        }
    }
    
    return total;
}

Answer 3

You could do

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

Answer 4

total += sum1.GetValueOrDefault();

etc.

Answer 5

How to about helper method -

static int Sum(params int?[] values)
{
  int total = 0;
  for(var i=0; i<values.length; i++) {
     total += values[i] ?? 0;
  }
  return total;
}

IMO, not very elegant but at least add as many numbers as you want in a one go.

total = Helper.Sum(sum1, sum2, sum3, ...);

Answer 6

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);