The dividend in the lambda expression is zero or null？-CodePudding

uses lambda expression to fetch data from the list:

listDatas.Sum(x => x.a / x.b)

But some x.b is zero,I try to do this，try to ignore counting data that divides by zero or null,also log error messages：

 public static decimal? SumNotZero<TSource>(this IEnumerable<TSource> source, Func<TSource, decimal?> selector)
        {
            decimal sum = 0;
            foreach (TSource item in source)
            {
                try
                {
                    decimal? v = selector(item);
                    if (v != null)
                    {
                        sum  = v.GetValueOrDefault();
                    }
                }
                catch (Exception ex)
                {
                   DoLog("The remainder is 0, and there is an error in filling in the data："   " "   ex);
                }
                
            }

            return sum;
        }

then use the function：

listDatas.SumNotZero(x => x.a / x.b)

But always report an error: System.DivideByZeroException: Attempted to divide by zero.

CodePudding user response：

Try something like:

listDatas.Sum(x => x.A / (x.B == 0 ? 1 : x.B));

Is not a beauty code, but works.

CodePudding user response：

Just for your Information, your code should work. Maybe you need to rebuild it. However, I wouldn't use it. Only use Exceptions for real Exceptions (because they are slow). The case you have here, is realy expected.

internal static class Program
{
    private static void Main(string[] args)
    {
        var list = new List<MyClass>
        {
            new MyClass(1, 0),
            new MyClass(10, 5)
        };
        Console.WriteLine(list.SumNotZero(x => x.A / x.B));
        Console.ReadKey();
    }

    public static decimal? SumNotZero<TSource>(this IEnumerable<TSource> source, Func<TSource, decimal?> selector)
    {
        decimal sum = 0;
        foreach (var item in source)
        {
            try
            {
                var v = selector(item);
                if (v != null)
                {
                    sum  = v.GetValueOrDefault();
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
        }

        return sum;
    }

    private class MyClass
    {
        public MyClass(int a, int b)
        {
            A = a;
            B = b;
        }

        public int A { get; }
        public int B { get; }
    }
}

If I were you, I would write it this way:

listDatas.Where(x => x.b != 0).Sum(x => x.a / x.b)

Or this way:

var sum = list.Sum(x =>
{
    if (x.B == 0)
    {
        return 0;
    }

    return x.A / x.B;
});
Console.WriteLine(sum);