C#

public LoadScreen ldScreen = null;  //the LoadScreen class

    public ExecQuery(ldScreen ld)
    {
        ldScreen = ld;
    }

 public void ececute()
 {
 /***some code here for preparation like path, filename etc***/

    conn = new SqlConnection(conString);

    server = new Server(new ServerConnection(conn));

    server.ConnectionContext.ExecuteNonQuery(script); //script is my textfile
 }

private void cancel_Click(object sender, EventArgs e)
    {
        ExecQuery exec = new ExecQuery(this);

        if (InvokeRequired)
        {
            BeginInvoke(new MethodInvoker(delegate() { exec.cancelProcess(); }));
        }

        else
        {
            exec.cancelProcess();
        }
    }

public void cancelProcess()
    {

       server.ConnectionContext.Cancel();
    }

An unhandled exception of type 'System.AccessViolationException' occurred in Unknown Module.

Additional information: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

If there is a handler for this exception, the program may be safely continued.