/Visual Studio 2008/CSWinFormDataGridView/JustInTimeDataLoading/MainForm.cs

/********************************* Module Header **********************************\

* Module Name:	JustInTimeDataLoading

* Project:		CSWinFormDataGridView

* Copyright (c) Microsoft Corporation.

* 

* This sample demonstrates how to use virtual mode in the DataGridView control 

* with a data cache that loads data from a server only when it is needed. 

* This kind of data loading is called "Just-in-time data loading". 

* 

* This source is subject to the Microsoft Public License.

* See http://www.microsoft.com/opensource/licenses.mspx#Ms-PL.

* All other rights reserved.

* 

* History:

* * 6/10/2009 3:00 PM Zhi-Xin Ye Created

\**********************************************************************************/



#region Using directives

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

using System.Data.SqlClient;

#endregion





namespace CSWinFormDataGridView.JustInTimeDataLoading

{

    public partial class MainForm : Form

    {

        public MainForm()

        {

            InitializeComponent();

        }



        private Cache memoryCache;



        // Specify a connection string. Replace the given value with a 

        // valid connection string for a Northwind SQL Server sample

        // database accessible to your system.

        private string connectionString =

            "Initial Catalog=NorthWind;Data Source=localhost;" +

            "Integrated Security=SSPI;Persist Security Info=False";



        private string table = "Orders";



        private void MainForm_Load(object sender, EventArgs e)

        {

            // Enable VirtualMode on the DataGridView

            this.dataGridView1.VirtualMode = true;



            // Handle the CellValueNeeded event to retrieve the requested cell value 

            // from the data store or the Customer object currently in edit.

            // This event occurs whenever the DataGridView control needs to paint a cell. 

            this.dataGridView1.CellValueNeeded += new

                DataGridViewCellValueEventHandler(dataGridView1_CellValueNeeded);



            // Create a DataRetriever and use it to create a Cache object

            // and to initialize the DataGridView columns and rows.

            try

            {

                DataRetriever retriever =

                    new DataRetriever(connectionString, table);

                memoryCache = new Cache(retriever, 16);

                foreach (DataColumn column in retriever.Columns)

                {

                    dataGridView1.Columns.Add(

                        column.ColumnName, column.ColumnName);

                }

                this.dataGridView1.RowCount = retriever.RowCount;

            }

            catch (SqlException)

            {

                MessageBox.Show("Connection could not be established. " +

                    "Verify that the connection string is valid.");

                Application.Exit();

            }

        }



        private void dataGridView1_CellValueNeeded(object sender,

            DataGridViewCellValueEventArgs e)

        {

            e.Value = memoryCache.RetrieveElement(e.RowIndex, e.ColumnIndex);

        }

    }

}