Datagridview cell double click event not working

private void dgvCust_CellDoubleClick(object sender, DataGridViewCellEventArgs e)
{
    try
    {
        if (IsList)
        {
            if (dgvCust.SelectedRows.Count >= 0)
            {
                mCustomerNo = dgvCust.Rows[e.RowIndex].Cells["No"].Value.ToString();
                OnCustomerChanged(mCustomerNo);
                this.Dispose();
            }
        }
        else
        {
            mNo = dgvCust.Rows[e.RowIndex].Cells["No"].Value.ToString();
            if (mNo != "")
            {
                FrmCustomerDetail objFrmCustDetail = new FrmCustomerDetail();
                FrmCustomerDetail.CustNo = mNo;
                FrmCustomerDetail.isLoading = true;
                objFrmMain.CheckOpened(objFrmCustDetail);
                objFrmMain.OpenForm(objFrmCustDetail, this);
            }
        }
    }
    catch (Exception Ex)
    {
        MessageBox.Show(Ex.Message);
    }
}