我的 c# 代码中出现“并非所有代码路径都返回值”错误

Question

I have written a c# extension method that returns any duplicate values in an array of ints and it is telling me that 'not all code paths return a value'. Here is my code:

public static int? FindDuplicate(this int[] arrayToFindDuplicateIn)
    {

        int previousint = int.MaxValue;
        arrayToFindDuplicateIn = arrayToFindDuplicateIn.OrderByDescending(x => x).ToArray();

        foreach (int number in arrayToFindDuplicateIn)
        {
            if (number == previousint)
            {
                return number;
            }
            else
            {
                return null;
            }

            previousint = number;
        }
    }

Answer 1

If the array is empty, no value is returned, so just return something at the end or check the input array with arrayToFindDuplicateIn.Any()

Answer 2

I think what you want is to remove your else return null; and put the return null; outside your foreach. Otherwise it will only loop once everytime.