ArrayPlusArray in my way and as lambda expression

ArrayPlusArray.cs

        private static int ArrayPlusArray(int[] arr1, int[] arr2)
        {
            int preSum1 = 0;
            int preSum2 = 0;

            for (int i = 0; i < arr1.Length; i++)
            {
                if (arr1[i] > 0)
                {
                    preSum1 += arr1[i];
                }
                else
                {
                    preSum1 += arr1[i];
                }
            }
            for (int i = 0; i < arr2.Length; i++)
            {
                if (arr2[i] > 0)
                {
                    preSum2 += arr2[i];
                }
                else
                {
                    preSum2 += arr2[i];
                }
            }
            return preSum1 + preSum2;
        }

ArrayPlusArray2.cs

        public static int ArrayPlusArray2(int[] arr1, int[] arr2)
        {
            return arr1.Sum(x => x) + arr2.Sum(x => x);
        }