Mega Code Archive
Asynchronous command processing using the callback approach (VB)
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<%@ Page Language="C#" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>
<%@ Import Namespace="System.Configuration" %>
<script runat="server">
Private Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
Dim DBCon As SqlConnection
Dim Command As SqlCommand = New SqlCommand()
Dim ASyncResult As SqlAsyncResult
DBCon = New SqlConnection()
Command = New SqlCommand()
DBCon.ConnectionString = _
ConfigurationManager.ConnectionStrings("DSN_NorthWind").ConnectionString
Command.CommandText = _
"SELECT TOP 5 Customers.CompanyName, Customers.ContactName, " & _
" Orders.OrderID, Orders.OrderDate, " & _
" Orders.RequiredDate, Orders.ShippedDate " & _
" FROM Orders, Customers " & _
" WHERE Orders.CustomerID = Customers.CustomerID " & _
" ORDER BY Customers.CompanyName, Customers.ContactName "
Command.CommandType = CommandType.Text
Command.Connection = DBCon
DBCon.Open()
AsyncResult = Command.BeginExecuteReader(New _
AsyncCallback(AddressOf CBMethod), CommandBehavior.CloseConnection)
End Sub
Public Sub CBMethod(ByVal ar As SQLAsyncResult)
Dim OrdersReader As SqlDataReader
OrdersReader = ar.EndExecuteReader(ar)
gvOrders.DataSource = OrdersReader
gvOrders.DataBind()
End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
<title>The Call Back Approach</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:GridView ID="gvOrders" Width="100%" AutoGenerateColumns="False"
Runat="server">
<Columns>
<asp:BoundField HeaderText="Company Name"
DataField="CompanyName"></asp:BoundField>
<asp:BoundField HeaderText="Contact Name"
DataField="ContactName"></asp:BoundField>
<asp:BoundField HeaderText="Order Date" DataField="orderdate"
DataFormatString="{0:d}"></asp:BoundField>
<asp:BoundField HeaderText="Required Date" DataField="requireddate"
DataFormatString="{0:d}"></asp:BoundField>
<asp:BoundField HeaderText="Shipped Date" DataField="shippeddate"
DataFormatString="{0:d}"></asp:BoundField>
</Columns>
</asp:GridView>
</div>
</form>
</body>
</html>
File: Web.config
<configuration>
<connectionStrings>
<add name="DSN_Northwind"
connectionString="Data Source=localhost\SQLEXPRESS;Initial Catalog=Northwind;Integrated Security=True"
providerName="System.Data.SqlClient" />
</connectionStrings>
</configuration>
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