C# quick sort

static void QuickSortDemo()
        {
            int[] arr = new int[] { 2, 5, -4, 11, 0, 18, 22, 67, 51, 6 };

            Console.WriteLine("Original array : ");
            foreach (var item in arr)
            {
                Console.Write(" " + item);
            }
            Console.WriteLine();

            QuickSort(arr, 0, arr.Length - 1);

            Console.WriteLine();
            Console.WriteLine("Sorted array : ");

            foreach (var item in arr)
            {
                Console.Write(" " + item);
            }
        }

        static int Partition(int[] arr,int left,int right)
        {
            int key = arr[left];
            while(true)
            {
                while(arr[left]<key)
                {
                    left++;
                }
                while(arr[right]>key)
                {
                    right--;
                }
                if(left<right)
                {
                    if(arr[left]==arr[right])
                    {
                        return right;
                    }
                    int temp = arr[left];
                    arr[left] = arr[right];
                    arr[right] = temp;
                }
                else
                {
                    return right;
                }
            }
        }

        static void QuickSort(int[] arr,int left,int right)
        {
            if(left<right)
            {
                int key = Partition(arr, left, right);
                if(key>1)
                {
                    QuickSort(arr, left, key - 1);
                }
                if(key+1<right)
                {
                    QuickSort(arr, key + 1, right);
                }
            }
        }

static int Partition(int[] arr,int low,int high)
        {
            int i = low;
            int j = high;
            int pivot = arr[low];
            while(i<j)
            {
                while(i<j && arr[j]>=pivot)
                {
                    j--;
                }
                if(i<j)
                {
                    arr[i++] = arr[j];
                }
                while(i<j && arr[i]<=pivot)
                {
                    i++;
                }
                if(i<j)
                {
                    arr[j--] = arr[i];
                }
            }
            arr[i] = pivot;
            return i;
        }

        static void QuickSort(int[] arr,int low,int high)
        {
            int pivot;
            if(low<high)
            {
                pivot = Partition(arr, low, high);
                QuickSort(arr, low, pivot - 1);
                QuickSort(arr, pivot + 1, high);
            }
        }