C#

private void btnSubmit_Click(object sender, EventArgs e)
        {

            if (tbRACFID.Text == string.Empty)
            {
                MessageBox.Show("You must have a RACFID in order to continue.", "RACFID Field Validation", MessageBoxButtons.OK, MessageBoxIcon.Stop);
                ff.ControlSetFocus(tbRACFID);
                return;
            }
            if (tbUserName.Text == string.Empty)
            {
                MessageBox.Show("You must have a User Name in order to continue.", "User Name Field Validation", MessageBoxButtons.OK, MessageBoxIcon.Stop);
                ff.ControlSetFocus(tbUserName);
                return;
            }

            PwdSecurity p = new PwdSecurity();
            uipc = this.Parent as UIPCMainForm;
            string strContainer = cbEndUserDepart.SelectedValue.ToString() + tbRACFID.Text.ToLower();
            DAL d = new DAL(uipc.StrUserName, p.base64Decode(uipc.StrPassword));
 
            this.backgroundWorker1.RunWorkerAsync();

            btnReset.PerformClick();
        }

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            PwdSecurity p = new PwdSecurity();
            uipc = this.Parent as UIPCMainForm;
            string strContainer = cbEndUserDepart.SelectedValue.ToString() + tbRACFID.Text.ToLower(); //ERROR Line
            DAL d = new DAL(uipc.StrUserName, p.base64Decode(uipc.StrPassword));

            BackgroundWorker worker = (BackgroundWorker)sender;

            //Obtain Propper Subnet IP Address based on the Router Type from the Routr table, and
            //the DMVPN Subnet Type from the SubntSize table

            string SubnetIPAddress = string.Empty;
            DataSet ds = new DataSet();
            ds = d.FillDropDowns(4); //Subnet Size IP
            foreach (DataRow dr in ds.Tables[0].Rows)
            {
                if (
                    dr["ROUTR_TYPE"].ToString() == cbRouter.Text &&
                    dr["LOC"].ToString() == cbLocation.SelectedValue.ToString())
                {
                    SubnetIPAddress = dr["SUBNT_IPADR"].ToString();
                }
            }

            d.importContainer(
            strContainer,
            tbUserName.Text,
            cbRouter.SelectedValue.ToString(),
            (int)arSubNetList[cbSubnet.SelectedIndex],
            cbSubnet.SelectedValue.ToString(),
            arDHCPOptionList[cbLocation.SelectedIndex].ToString(),
            arDHCPPolicyList[cbLocation.SelectedIndex].ToString(),
            SubnetIPAddress,
            arAllocationTemplateList[cbSubnet.SelectedIndex].ToString()
            );
  
        }

        private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            this.tsProgBar.Value = e.ProgressPercentage; 
            this.tslStatus.Text = e.UserState as string;
        }

        private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            this.tslStatus.Text = "Operation complete";
        }