14.5. Deploying ASP.Net Web Applications
Virtuoso is a CLR host. It is responsible for initializing the runtime, defining the application domain (its runtime boundaries, security settings, etc), and executing user code within such domains. Windows can be used as the development platform, a very developer friendly environment with a rich set of tools, but you will not be restricted to Windows, .NET and IIS to run the assemblies produced. Where .NET is not readily available or desired Virtuoso contains Mono, an open source re-implementation of Microsoft .NET, a vehicle taking .NET cross-platform.
The CLR run-time is a part of the Virtuoso process. The Mono run time may be run either as in-process or as out-of-process. Hosted applications can make use of the regular Virtuoso .Net data provider to access Virtuoso SQL data and procedures. Microsoft ASPX files can also be run directly from Virtuoso either from the file system or WebDAV. Each of these capabilities releases you from the Microsoft platforms without compromising your development platform.
The Virtuoso CLR hosting is implemented using the VSEI.
Figure 14.16. The HTTP ASP.Net handler
![[Tip]](images/tip.png)
14.5.1. Programming Concepts
ASP.Net Web Forms are divided into two sections: the user interface and the application logic. The user interface comprises HTML markup and ASP.Net web controls whereas the application logic contains all the programming code that allows the controls to interact with themselves and the server back-end. This provides the level of abstractions required for dynamic efficient Web application design. The interface can be altered without any backward or forward dependence on the code (logic). The Web Form interface should be created with the .aspx extension. The application logic can be contained in-line within the ASPX application, but developers should strive to keep the code in a separate location known as the "CodeBehind". This is a file that contains the logic (code) for the Web Form which should end in an extension appropriate for the programming language used, such as .vb for Visual Basic or .cs for C#. The CodeBehind can be written in any language for which there is a .Net compiler for. The compiler generates bytecode that can be deployed anywhere the .Net runtime exists.
The ASPX Web Form is compiled into an object that takes its place on a tree of controls and classes. The CodeBehind is compiled into an object on this tree when the page is requested. The Web Form must inherit from a "base-class" defined in the CodeBehind class file.
Figure 14.17. ASPX Web Form class hierarchy
Now we will create a new Web Form containing an HTML heading and an ASP.Net DataGrid control that will display results from the local Virtuoso server.
Example 14.50. Sample .Net Web Application: VirtTest.aspx
<%@ Page Language="vb" Inherits="VirtTest" Src="VirtTest.aspx.vb" %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <html> <head> <title>Virtuoso Provider to DataGrid in VB</title> </head> <body> <h1>Simple VB Virtuoso DataBinding Demo</h1> <form xml:id="form1" method="post" runat="server"> <asp:DataGrid id=DataGrid1 runat="server" DataMember="Customers" BorderColor="silver" BorderWidth="1" CellPadding="2" Font-Name="Tahoma" Font-Size="10pt"> <HeaderStyle BackColor="#2222ff" ForeColor="yellow"/> <PagerStyle Mode="NextPrev" /> </asp:DataGrid> </form> <hr> </body> </html>
On the first line of the file we use the
@ page
directive to inherit the
CodeBehind class we will create in the CodeBehind file. The source of which can be
optionally declared here with the Src=
attribute. Visual Studio makes use of
CodeBehind=
for tracking associated
source code instead. If either of these two attributes are specified then
the .Net runtime will attempt to compile the code into an assembly
(DLL) upon first execution if it does not already exist or seems out-of-date.
The following code fragment is the CodeBehind, VirtTest.aspx.vb.
Now we want some logic behind the Web Form. We have placed a DataGrid control on a web page but we need to supply data to it now:
Example 14.51. Sample .Net Web Application CodeBehind: VirtTest.aspx.vb
imports System
imports System.Web
imports System.Web.UI
imports System.Web.UI.WebControls
imports System.Web.UI.HtmlControls
imports System.Data
imports OpenLink.Data.VirtuosoClient
Public Class VirtTest
Inherits Page
Protected WithEvents myConnection As OpenLink.Data.VirtuosoClient.VirtuosoConnection
Protected WithEvents myCommand As OpenLink.Data.VirtuosoClient.VirtuosoDataAdapter
Protected WithEvents DataGrid1 As System.Web.UI.WebControls.DataGrid
Protected WithEvents ds As System.Data.DataSet
Private Sub Page_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim myConnection As new VirtuosoConnection("HOST=noodle:1112;UID=dba;PWD=dba;Database=Demo")
Dim myCommand As new VirtuosoDataAdapter("select * from Demo..Customers", myConnection)
Dim ds As new DataSet()
myCommand.Fill(ds, "Customers")
DataGrid1.DataSource=ds.Tables("Customers")
DataGrid1.DataBind()
End Sub
End Class
This file is compiled using the following command (split across lines for readability and would otherwise all be on one line):
E:\myweb\myapp>
vbc /target:library
/r:System.dll
/r: System.Web.dll
/r:System.Data.dll
/r:OpenLink.Data.VirtuosoClient.dll
/r:System.Xml.dll
/out:bin\VirtTest.dll
VirtTest.aspx.vb
Once compiled, the resulting DLL library should be in the bin subdirectory
of the application root. When the assembly is available in this way the .aspx
file does not need to contain the Src=
attribute since there will be no need to compile the CodeBehind. If the
Src=
attribute is specified in the .aspx file
but the CodeBehind file is not located on the server then an error will be signalled
indicating that a required resource cannot be found, because the CodeBehind
class is compiled on demand.