C#

private void dgvFactorSell_CellValidating(object sender, DataGridViewCellValidatingEventArgs e)
        {

if (dgvFactorSell.Rows[e.RowIndex].Cells["CStoreCode"].EditedFormattedValue != null && dgvFactorSell.Rows[e.RowIndex].Cells["CStoreCode"].EditedFormattedValue.ToString() != "")
                        {
                                                  e.Cancel = true;
                        }}

bool FlagIsClose = false;
const int HTCLOSE = 0x14;
const int WM_NCLBUTTONDOWN = 0xA1;
protected override void DefWndProc(ref Message m)
 {
   if (m.Msg == WM_NCLBUTTONDOWN)
     {
       if (m.WParam.ToInt32() == HTCLOSE)
        {
          FlagIsClose = true;
        }
     }
   base.DefWndProc(ref m);
 }

BackgroundWorker bwAsync = new BackgroundWorker();

public Form1() {
    InitializeComponent();

    bwAsync.WorkerReportsProgress = true;
    bwAsync.WorkerSupportsCancellation = true;
    bwAsync.DoWork += new DoWorkEventHandler(bwAsync_DoWork);
} 

private void button1_MouseDown(object sender, MouseEventArgs e) {

    bwAsync.RunWorkerAsync();
}

private void button1_MouseUp(object sender, MouseEventArgs e) {

    bwAsync.CancelAsync();
}


void bwAsync_DoWork(object sender, DoWorkEventArgs e) {

    BackgroundWorker bwAsync = sender as BackgroundWorker;

    int i;
    label1.Invoke( (MethodInvoker)delegate()
    {
        i = int.TryParse(label1.Text, out i) ? i : 0;
        while(!bwAsync.CancellationPending){
            Console.WriteLine("down");
            label1.Text = i.ToString();
            i++;
        }
    });
}

connectionString1 = @"
            server = .\sqlexpress;
            integrated security = true;
            database = C:\Program Files\Microsoft SQL Server\MSSQL10.SQLEXPRESS\MSSQL\DATA\NORTHWND.MDF;
user instance = true";

connectionString2 =  @"
            server = .\sqlexpress;
            integrated security = true;
            database = northwind";