Reshaper highlights n.Value saying that there is a possibility of InvalidOperationException.

FalseWarning.cs

using System.Linq;

namespace Nullable
{
    public class Nullable_Test
    {
	public void SumNullableNumbers()
	{
		int?[] numbers = new int?[10];
		int sum = numbers.Where(n => n.HasValue).Sum(n => n.Value);
	}
    }
}