Create next smallest number from the same array element

Create next smallest number from the same array element

 class Program
    {
        public static void Main(string[] args)
        {
            var matrix = new int[] { 2, 5, 8, 7, 6, 1 };

            var loopLength = matrix.Length - 1;
            var firstSmallElementIndex = -1;

            //1. Find the index where there's small element on left hand side
            while (loopLength >= 0)
            {
                if (loopLength - 1 <= 0)
                    break;

                if (matrix[loopLength] > matrix[loopLength - 1])
                {
                    firstSmallElementIndex = loopLength;
                    break;
                }
                loopLength--;
            }

            //2. From First found small element, start first small element in right hand side
            loopLength = matrix.Length - 1;

            var startIndex = firstSmallElementIndex + 1;
            var smallestElementOnRightSideIndex = -1;
            var smallestElementOnRightSide = matrix[startIndex];

            while (startIndex <= loopLength)
            {
                if (smallestElementOnRightSide > matrix[startIndex])
                {
                    smallestElementOnRightSide = matrix[startIndex];
                    smallestElementOnRightSideIndex = startIndex;
                }
                startIndex++;
            }

            //3. Swap Element
            SwapElement(matrix, firstSmallElementIndex, smallestElementOnRightSideIndex);

            //4. Sort Element 
            Array.Sort(matrix, firstSmallElementIndex, loopLength - firstSmallElementIndex);
            Console.WriteLine($"Solution: {string.Join(",", matrix)}");


            Console.Read();
        }

        private static void SwapElement(int[] matrix, int start, int end)
        {
            var a = matrix[start];
            matrix[start] = matrix[end];
            matrix[end] = a;
        }
    }