Get comma separated values of checked items values of CheckedListBox and pass on to the Where condition in the query

string whereCndn = string.Empty;
foreach (var item in ChkM.SelectedItems)
        {
            if (item.Selected)
            {
               whereCndn += item.SelectedValue + ","; //Here you will get set of selected checkbox value like (8,9,)
            }
        }

        string str = "select * from table_name where t_id IN ("+ whereCndn.Remove(whereCndn.Length - 1) +")"; //Removing last comma character from the string and putting it in string
               DataTable dt = new DataTable();
                dt = con.select(str);
                if (dt.Rows.Count >= 1)
                {
                    rptr.DataSource = dt;
                    rptr.DataBind();
                }