ASP.NET Database Connection

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# ASP.NET - Database Connection

ADO.NET is also a part of the .NET Framework. ADO.NET is used to handle data access. With ADO.NET you can work with databases.

## Examples

Database connection - Bind to a Repeater control

Database connection - Bind to a DataList control

## What is ADO.NET?

- ADO.NET is a part of the .NET Framework
- ADO.NET consists of a set of classes used to handle data access
- ADO.NET is entirely based on XML
- ADO.NET has, unlike ADO, no Recordset object

## Create a Database Connection

We are going to use the Northwind database in our examples.

First, import the "System.Data.OleDb" namespace. We need this namespace to work with Microsoft Access and other OLE DB database providers. We will create the connection to the database in the Page_Load subroutine. We create a dbconn variable as a new OleDbConnection class with a connection string which identifies the OLE DB provider and the location of the database. Then we open the database connection:

    <%@ Import Namespace="System.Data.OleDb" %>

    <script runat="server">
    sub Page_Load
    dim dbconn
    dbconn=New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;
    data source=" & server.mappath("northwind.mdb"))
    dbconn.Open()
    end sub
    </script>

Note: The connection string must be a continuous string without a line break!

## Create a Database Command

To specify the records to retrieve from the database, we will create a dbcomm variable as a new OleDbCommand class. The OleDbCommand class is for issuing SQL queries against database tables:

    <%@ Import Namespace="System.Data.OleDb" %>

    <script runat="server">
    sub Page_Load
    dim dbconn,sql,dbcomm
    dbconn=New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;
    data source=" & server.mappath("northwind.mdb"))
    dbconn.Open()
    sql="SELECT * FROM customers"
    dbcomm=New OleDbCommand(sql,dbconn)
    end sub
    </script>

## Create a DataReader

The OleDbDataReader class is used to read a stream of records from a data source. A DataReader is created by calling the ExecuteReader method of the OleDbCommand object:

    <%@ Import Namespace="System.Data.OleDb" %>

    <script runat="server">
    sub Page_Load
    dim dbconn,sql,dbcomm,dbread
    dbconn=New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;
    data source=" & server.mappath("northwind.mdb"))
    dbconn.Open()
    sql="SELECT * FROM customers"
    dbcomm=New OleDbCommand(sql,dbconn)
    dbread=dbcomm.ExecuteReader()
    end sub
    </script>

## Bind to a Repeater Control

Then we bind the DataReader to a Repeater control:

    <%@ Import Namespace="System.Data.OleDb" %>

    <script runat="server">
    sub Page_Load
    dim dbconn,sql,dbcomm,dbread
    dbconn=New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;
    data source=" & server.mappath("northwind.mdb"))
    dbconn.Open()
    sql="SELECT * FROM customers"
    dbcomm=New OleDbCommand(sql,dbconn)
    dbread=dbcomm.ExecuteReader()
    customers.DataSource=dbread
    customers.DataBind()
    dbread.Close()
    dbconn.Close()
    end sub
    </script>

    <html>
    <body>

    <form runat="server">
    <asp:Repeater id="customers" runat="server">

    <HeaderTemplate>
    <table border="1" width="100%">
    <tr>
    <th>Companyname</th>
    <th>Contactname</th>
    <th>Address</th>
    <th>City</th>
    </tr>
    </HeaderTemplate>

    <ItemTemplate>
    <tr>
    <td><%#Container.DataItem("companyname")%></td>
    <td><%#Container.DataItem("contactname")%></td>
    <td><%#Container.DataItem("address")%></td>
    <td><%#Container.DataItem("city")%></td>
    </tr>
    </ItemTemplate>

    <FooterTemplate>
    </table>
    </FooterTemplate>

    </asp:Repeater>
    </form>

    </body>
    </html>

## Close the Database Connection

Always close both the DataReader and database connection after access to the database is no longer required:

    dbread.Close()
    dbconn.Close()

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