C# - Sum List having some null-CodePudding

In my apps I will need to handle null value in a list.

Is there a way to do a sum in a foreach without using an if statement to check if an item is null in the list.

List<int?> numberList = new();
numberList.Add(32);
numberList.Add(21);
numberList.Add(null);
numberList.Add(11);
numberList.Add(89);
int? result = 0;
    
foreach (var item in numberList)
{
    if (item != null)
    {
        result  = item;
    }   
}
Console.WriteLine($"with if statement Value is : {result}");

CodePudding user response：

Is there a way to do a sum in a foreach without using an if statement to check if an item is null in the list.

Sure, you could use GetValueOrDefault:

foreach (var item in numberList)
{
    result  = item.GetValueOrDefault(); 
}

But then you lose the information if there was at least one item != null, because you'd treat a null item same as an item that is 0. Of course you can shorten code with LINQ:

int result = numberList.Sum(i => i.GetValueOrDefault());

CodePudding user response：

You can make use of LINQs Sum. Just use it in combination with the Coalescing Operator which allows to specify an explicit default value in case of null:

int sum = numberList.Sum(n => n ?? 0);

or more simple to use 0 as default:

int sum = numberList.Sum();

Note that you need to define usage of LINQ like

using System.Linq;

Without LINQ, you can also make use of the Coalescing Operator:

foreach (var item in numberList)
{
    result  = item ?? 0;
}

Note that this is from a runtime point of view exactly the same like you've showed in your example, it's just syntactic sugar.