public partial class MainForm : Form
{
    //
    // Indicates the a query is being processed
    //
    Boolean _processing = false;
            
    TdConnection _cn = null;
    String _connectionString = @"Data Source=Teradata1; " +
               "Initial Catalog=ProdDB; " +
               "Integrated Security=True;Pooling=False";
            
    private delegate void WarehouseGridDelegate(TdDataReader warehouseReader);
            
    public MainForm()
    {
        InitializeComponent();
    }
            
    private void WarehouseGrid(TdDataReader warehouseReader)
    {
        try
        {
            //setting up the data table that will be 
            //passed onto the DataGrid to display the 
            //warehouse locations.
            DataTable warehouseTable = new DataTable();
            warehouseTable.Load(warehouseReader);
            
            //populating the data grid.
            this.dataGridWarehouse.DataSource = warehouseTable;
        }
        catch (Exception e)
        {
            MessageBox.Show(e.Message, "ERROR");
        }
        finally
        {
            warehouseReader.Close();
            _cn.Close();
        }
    }
            
    private void WarehouseCallback(IAsyncResult result)
    {
        TdCommand command = (TdCommand)result.AsyncState;
            
        TdDataReader warehouseReader = command.EndExecuteReader();
            
        _processing = false;
            
        //Need to setup a delegate that will be invoked by 
        //the form's Invoke method.  The reason for this is that
        //this callback will be running on a different thread than the
        //form's thread. Interaction of the form and its contents 
        //can only be done from the main thread, not from a 
        //worker thread.
        WarehouseGridDelegate wg = 
                  new WarehouseGridDelegate(WarehouseGrid);
            
        this.Invoke(wg, warehouseReader);
    }
             
    private void buttonSubmit_Click(object sender, EventArgs e)
    {
        //checking whether the form is already processing another query
        if (true = _processing)
        {
            MessageBox.Show("Currently retrieving warehouse information");
        }
        else
        {
            String warehouseSQL = "select ProdCount, WarehouseName, " +
                                    "WarehouseCity, WarehouseState " +
                                    "from ProductWarehouse " +
                                    "where ProdNo= " + textBoxProdNo.Text";
            
            try
            {
                _processing = true;
            
                _cn = new TdConnection(_connectionString);
            
                TdCommand command = _cn.CreateCommand();
                command.CommandText = warehouseSQL;
            
                //setting up the delegate for the asynchronous call
                AsyncCallback callback = 
                         new AsyncCallback(WarehouseCallback);
            
                //asynchronous call.  The WarehouseCallback callback will be
                //invoked by the provider after processing of the query has
                //been completed.
                command.BeginExecuteReader(callback, command);
            }
            catch (TdException t)
            {
                MessageBox.Show(t.Errors[0].Message);
            
                _cn.Close();
            }
        }
    }
}