autodecrement in number using c#

Question

How do I autodecrement the number of students allowed everytime you assign a section to each student added?

I have the code, but it has an error.

    private void btnAssign_Click(object sender, EventArgs e)
    {
        ////for auto increment
        ds = DBConn.getStudentDetails("sp_Retrieve_Student_Section");
        int cnt = ds.Tables[0].Rows.Count;
        string lastrec = ds.Tables[0].Rows[cnt+1][1].ToString();
        int newpcode = int.Parse(lastrec) - 1;
        txtAllowed.Text= newpcode.ToString();



    }

Answer 1

At first glance it looks like this line:

string lastrec = ds.Tables[0].Rows[cnt+1][1].ToString();

cnt+1 is out of the bounds of the collection, and an exception probably told you this. You are probably looking for cnt-1.

Answer 2

I'd probably write

 int newpcode = int.Parse(lastrec) - 1;

as

int newpcode = 0;
if(Int32.TryParse(lastrec, out newpcode))
{
   newpcode--;
}

That way, if it can successfully parse the lastrec, it will decrement. If it can't successfully parse, your newpcode will be 0, but will not throw an error.