INTRODUCING DATA ACCESS WITH ADO.NET

ost production-grade applications need some form Mof data access. Data access in the .NET Framework

is simplified for you through the ADO.NET Framework classes. These classes are found in System.Data namespace, which has two major namespaces: one for SQL Server data stores and another for data stores that can be accessed through OLE DB.

The SQL Server .NET Data Provider classes come from the System.Data.SqlClient namespace. The SQL Server

.NET Data Provider uses its own protocol to communicate with SQL Server. The provider is lightweight and performs well, accessing a SQL Server data source directly without adding an OLE DB or Open Database Connectivity (ODBC) layer. When you need to work with other database besides Microsoft SQL Server, you should use the OLE DB .NET Data Provider, which you can find in the

System.Data.OleDb namespace.

If you are familiar with ADO, you may notice some similaries when accessing data in C# with ADO.NET. The Connection and Command objects, for example, have almost identical properties and methods. The brand new part in ADO.NET is in the area of reading and persisting records of data. In the days of ADO, Recordsets transported returned data from a SQL database; however, in ADO.NET, the Recordset is gone, replaced by things like the DataSet,

DataReader, DataTables, and DataViews.

To orient you to ADO.NET’s new object model, these pages outline a few key members of the ADO.NET classes (System.Data namespace). Because both the

System.Data.SqlClient and System.Data.OleDb implement most of the same base classes, the examples reflect the perspective of only one of the providers,

SqlClient.

You can use the DataGrid Web Server Control to build tables containing data. One of the advantages of using the DataGrid Web Server Control is not having

to manually construct the table. Because you will bind DataGrid control to data, you do not have to programmatically loop through DataSets and other data structure types, nor write out table tags, formatting, and data field values as you hit each record in the data storage.

The process of binding to a DataGrid is quite simple. First you must retrieve a data source. Then you assign that data

source to the DataSource property of the DataGrid control. Lastly, you call the DataBind method of the

DataGrid control.

The data source for the DataGrid control will most likely be a database, but the control is not restricted to binding to only traditional database stores. For example, ADO.NET data structures can be built from other providers like Exchange, WebDav, and Active Directory. Also, any lists derived from ICollection can also be used as a data source.

more ■ The form's code-behind server page appears with the

Page_Load event handler.

page. › Add a SqlConnection variable and initialize with a valid connection string to your database.

ˇ Add a SqlDataAdapter variable and initialize with a valid select statement.

The DataGrid Web Server Control has paging capabilities that are used to display a result into multiple navigable pages. When the page index changes, the CurrentPageIndex attribute on the DataGrid needs to be set.

TYPE THIS:

<SCRIPT language="C#" runat="server">

void Page_Load(object sender, System.EventArgs e){ if (!IsPostBack)

BindData(); }

void Grid_Change(Object sender, DataGridPageChangedEventArgs e){ dgdTitles.CurrentPageIndex = e.NewPageIndex; BindData(); }

void BindData() {

SqlConnection cnPubs = new SqlConnection( "server=(local);uid=sa;pwd=;database=pubs");

SqlDataAdapter daTitles = new SqlDataAdapter( "select title, notes, price, pubdate "

+ "from titles", cnPubs); DataSet dsTitles = new DataSet(); daTitles.Fill(dsTitles, "titles"); dgdTitles.DataSource=

dsTitles.Tables["titles"].DefaultView; dgdTitles.DataBind(); }

</SCRIPT>

RESULT:

An HTML page with an HTML table containing all rows in the titles table for the specified columns.

Á Add a DataSet variable and use the Fill method of the DataAdapter to populate the DataSet.

‡ Set the DataSource property for the data grid to the DataSet created and use the DataBind method to bind the DataGrid.

° Build and browse the Web page.

Note: See page 220 for more information on building and browsing a Web page.

■ The data returned from the select statement is displayed in the DataGrid.

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