Problem with QuickSort algorithm in C#

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C#

algorithm

Hi friends, I wrote a quicksort algorithm in c# but it has a problem,when I compile it, it doesn't work in some conditions. For example when I enter number 12, 32, 11 in textbox6 to sort, it gives out of range error. When I go to trace it, debugger shows that num[] took nums[0]=12, nums[1]=11, nums[2]=1 I commented in the lines of problem, thanks in advance

Edited: I changed the while condition and it now doesn't give out of range error but when the input is 12,32,11 output 11,12,1

private void button5_Click(object sender, EventArgs e)
    {
        string[] x = textBox6.Text.Split(',');
        int[] nums = new int[x.Length];
    
        for (int counter = 0; counter < x.Length; counter++)
        {
            nums[counter] = Convert.ToInt32(x[counter]);
        }
        int i = 0;
        int  j = nums.Length;
        int pivot = nums[0];
        do
        {
            do
            {
                    i++;
            }
                while ((i < nums.Length) && (nums[i] < pivot));

            do
                {
                    j--;
                }
while (nums[j]>pivot);
            if (i < j)
            {
                int temp = i;
                nums[i] = nums[j];
                nums[j] = temp;
            }
        }while(i<j);
        int temp1 = nums[0];
        nums[0] = nums[j];
        nums[j] = temp1;
        int pivotpoint = j;
        string QuickSort = "";
        foreach (var n in nums)
           QuickSort += n.ToString() + ",";
        textBox5.Text = QuickSort;
    }