ASP.net Architecture

Jeremy Boyd, Senior Technical Lead - Intergen MSDN Regional Director – New Zealand

A quick word about the RD program

 Regional Directors aren't Microsoft employees RDs are independent developers who provide a link between Microsoft and the local community. Find out more: http://www.microsoft.com/rd Drop us a line if you want to talk shop, ask about the new technology coming out of Microsoft, or just see if we can help with a technical problem you are having  New Zealand RDs – Lukas Svoboda, Jeremy Boyd Australia RDs – Adam Cogan, Peter Stanski

Objectives

Discuss history of ASP.NET

– Dynamic web content – ASP Present new ASP.NET architecture – .NET core – Compilation – Code behind – Shadow copying Migration from ASP

Dynamic Web Content

Dynamic web content has traditionally been generated using CGI, ISAPI, or ASP on Microsoft platforms – The Common Gateway Interface (CGI) provides dynamic content by directly processing requests and issuing responses in a custom process – The Internet Services API provides similar capability through filter DLLs, reducing the overhead – Active Server Pages (ASP) eliminates the need to author DLLs to provide dynamic content - integrated server-side script generates HTML

ASP

Active Server Pages (ASP) simplify common tasks ISAPI DLLs were being used for – ASP was introduced because web developers were building ISAPI extension DLLs to perform things like database queries and posting back HTML – Each different type of request required a new ISAPI extension DLL to be written – ASP.DLL is a generic ISAPI DLL that reads .ASP files, parses and executes server side script blocks, and serves up result

ASP.NET == ASP.NExTversion

On one hand, ASP.NET is an evolution of the ASP and is just the next version of ASP – Same intrinsic objects available – Script and html can be mixed – Some ASP code can be ported with no changes – Server-side Javascript is still supported

Sample ASP file

server-side directive server-side function server-side evaluation syntax < script function language ='JScript' Add(x, y) { return x+y; } runat ='server'> < html > < body > < h1 > Test ASP Page < h2 > 2+2=<%=Add(2,2)%> %> h2 > < table <% for border ='2'> table > ( var i=0; i<10; i++) { %> %> < tr >< td > %> < td > <% %> interspersed server-side script test.asp

%>

Fundamental change

ASP.NET is more than just the next version of ASP – Pages are compiled into assemblies improving performance and diagnostics – Code-behind encourages better separation of code from HTML – Extensible, server-side control architecture – Server-side data binding model – Form validation architecture – Web services allow assemblies to expose themselves as SOAP servers

Sample ASP.NET file

server-side directive server-side function server-side evaluation syntax < int Add(int x, int y) { script runat ="server"> return x+y; } < html > < body > < h1 > Test ASP.NET Page < h2 > 2+2=<%=Add(2,2)%> %> h2 > < table border ="2"> <% for (int i=0; i<10; i++) { %> < tr >< td > <% %> < td > %> <% %> table > interspersed server-side script test.aspx

%>

What is ASP.NET?

At a high level, ASP.NET is a collection of .NET classes that collaborate to process an HTTP request and generate an HTTP response – Some classes are loaded from system assemblies – Some classes are loaded from GAC assemblies – Some classes are loaded from local assemblies – To work with ASP.NET, you must build your own classes that integrate into its existing class structure – Some of your classes will be in pre-built assemblies – Some of your classes will be in assemblies generated implicitly from ASP.NET files (aspx, ashx, asmx, ...)

High-level view of ASP.NET

HTTP Request GET /foo/foo.aspx

HTTP Response HTTP/1.1 200 OK ...

ASP.NET Worker Process AppDomain1 System Assemblies system.web.

dll system.data.

dll mscorsvr.dll

GAC Assemblies bargraph.dll

mygacutil.dll

acmeutil.dll

Local Assemblies mypage.dll

32wie4kg.dll

myctrl.dll

Pipeline architecture

ASP.NET uses the CLR to replace IIS's ISAPI/ASP architecture – User-defined handler objects used to dispatch HTTP requests – Requests dispatched through ASP.NET-provided ISAPI extension (

aspnet_isapi.dll

) – Handlers run in an ASP.NET-provided worker process (

aspnet_wp.exe

in IIS 5,

w3wp.exe

in IIS 6) – Many IIS features bypassed in favor of ASP.NET provided features (WAM-based process isolation, ASP object model, and session management)

HttpPipeline architecture (IIS 5.0)

GET /foo/foo.aspx

HTTP/1.1 200 OK ...

Web Server (Win2000, XP) aspnet_isapi.dll

(ISAPI Extension) aspnet_wp.exe

(ASP.NET Worker Process) named pipe connection IHttpHandler handler INETINFO.EXE (IIS 5.0)

HttpPipeline architecture (IIS 6.0)

Web Server (Win Server 2003) Application Pool #1 w3wp.exe

(ASP.NET Worker Process) IHttpHandler handler Application Pool #2 w3wp.exe

(ASP.NET Worker Process) IHttpHandler handler aspnet_isapi.dll

(ISAPI Extension) aspnet_isapi.dll

(ISAPI Extension) kernel http.sys

GET /foo/foo.aspx

HTTP/1.1 200 OK ...

Compilation vs. Interpretation

When ASP.NET pages are first accessed, they are compiled into assemblies – Subsequent access loads the page directly from the assembly – Eliminates inefficiencies of the scripting model of ASP – No performance difference between compiled components and embedded server-side code – Debugging tools shared with all .NET development – Whenever you author a new .aspx file, you are authoring a new class

Page compilation

Every ASP.NET page is compiled into an assembly on first access – The generated assembly contains a single class that derives from

System.Web.UI.Page

– The generated

Page

-derived class is the file name of the page, replacing the "." with a "_" (like

foo_aspx

) – The generated assembly is stored in the 'Temporary ASP.NET Files' directory on the server machine

ASP.net Page Compilation

HTTP Request GET /foo/foo.aspx

IIS & ASP.NET

PageParser:: GetCompiledPageInstance HTTP Response HTTP/1.1 200 OK ...

Content-Type: text/html; Content-Length: 300 ...

Locate foo.aspx

Generate Page-derived class foo_aspx from file Compile to assembly no Compiled assembly already exists?

yes Create foo_aspx instance Call Page::ProcessRequest Page::ProcessRequest calls Page::RenderControl

ASP.NET basics

Each ASP.NET page is parsed and compiled into a class that extends System.Web.UI.Page

– Page class implements

IHttpHandler

– A lot of the

Page

class is dedicated to forms/control processing – Exposes

HttpContext

properties as own properties

.aspx Type Information

<%@ Page Language='C#' %>

Show Page Type

<% Response.Output.Write("

Page type {0}

", this.GetType()); Response.Output.Write("

Page base type {0}

", this.GetType().BaseType); %>

System.Web.UI.Page

The Page class provides facilities for rendering HTML –

Response

and

Request

objects are available as properties of the class – Methods for rendering are provided – Events associated with generating the page are defined

System.Web.UI.Page

class { Page : TemplateControl, IHttpHandler // State management public HttpApplicationState Application { get ;} public public HttpSessionState Session { virtual get ;} Cache Cache { get ;} // Intrinsics public HttpRequest Request { get ;} public public HttpResponse Response { HttpServerUtility Server { public string MapPath( string get ;} get ;} virtualPath); } // Client information public string public ClientTarget { IPrincipal User { get get ;} ; set ;} //...

System.Web.UI.Page

class { Page : TemplateControl, IHttpHandler // Core public UserControl LoadControl( string public virtual virtualPath); ControlCollection Controls { get ;} public override string ID { get ; set ;} public bool IsPostBack { get ;} protected virtual void RenderControl(HtmlTextWriter writer); // Events public event public event public event public event EventHandler Init; EventHandler Load; EventHandler PreRender; EventHandler Unload; } //...

Class creation

Classes created from .aspx files can be customized – Server-side script blocks are added to the class definition • Member variables • Member functions – Interspersed script is added to a 'Render' function • Executable code

Aspx == Class

member variable declaration member function declaration member function usage member variable usage <%@ Page Language="C#" %> < <%@ Page Language="C#" %> html >< body > < script { language ="C#" runat ="server"> private ArrayList _values = new ArrayList(); private void PopulateArray() _values.Add("v1"); _values.Add("v2"); _values.Add("v3"); _values.Add("v4"); } < h2 > aspx==class!

< ul > PopulateArray(); for (int i=0; i<_values.Count; i++) Response.Output.Write("

{0}

", _values[i]); %>

Server Side Code Placement in Page Compilation

<%@ Page Language="C#" %>

<% PopulateArray(); for (int i=0; i{0}", m_values[i]); %>

// Machine-generated source file // ybngvkuj.0.cs

namespace ASP { public class SamplePage_aspx : Page, IRequiresSessionState { private ArrayList m_values = new ArrayList(); private void PopulateArray() { m_values.Add("v1"); m_values.Add("v2"); m_values.Add("v3"); m_values.Add("v4"); } public SamplePage_aspx() { /*...*/ } private void __Render__control1( HtmlTextWriter __output, Control parameterContainer) { __output.Write( "\r\n"); __output.Write( "\r\n\r\n"); __output.Write("\r\n

\r\n"); PopulateArray(); for (int i=0; i{0}", m_values[i]); __output.Write( "\r\n

\r\n \r\n"); } //...

} }

Code behind

In addition to customizing the generated Page class using embedded code, ASP.NET supports page inheritance – Technique of

Page

inheritance is called code behind – Supported through the

Inherits Page

directive attribute of the – Promotes separation of code and presentation – Code-behind files can be pre-compiled and placed in a directory named /bin at the top level of the application – Code-behind files can be compiled on demand

Sample Page with CodeBehind

<%@ Page Language="C#" Inherits="EssentialAspDotNet.Architecture.SamplePage"%> < html >< body > < h2 > aspx==class!

< ul > <% WriteArray(); %> %>

SamplePage.cs

namespace { EssentialAspDotNet.Architecture

public class { SamplePage : Page ArrayList(); private public ArrayList _values = SamplePage() new { _values.Add("v1"); _values.Add("v2"); _values.Add("v3"); _values.Add("v4"); } } } protected void { WriteArray() for ( int i=0; i<_values.Count; i++) Response.Output.Write("

{0}

", _values[i]); }

Class Hierarchy created using code behind

System.Web.UI.Page

EssentialAspDotNet.

Architecture.

SamplePage ASP.CodeBehind_aspx

Using src attribute to automatically compile code behind <%@ Page Language="C#" src="SampleCodeBehind.cs" Inherits="EssentialAspDotNet.Architecture.SamplePage"%> < html >< body > < h2 > aspx==class!

< ul <% > <% WriteArray(); %> %>

Shadow Copying

All assemblies in the /bin directory are shadow copied – Placing assemblies in /bin makes them available to all pages in that application – These assemblies are not referenced directly by ASP.NET

– Instead they are copied to an obscure location prior to loading – If the original file ever changes, the file is re-copied – Enables xcopy deployment

Shadow Copy Mechanism

ShadowCopyDirectories Referenced Assembly (Original) Copied by assembly loader Shadow Copy (actually loaded) Fusion managed directories

ASP->ASP.NET Migration

Several options for migrating 'classic' ASP applications – Run ASP side-by-side with ASP.NET, developing new pages/apps in ASP.NET

• Quickest path, but session and application state is not shared – Convert existing ASP pages to ASP.NET (but keep using old libraries - ADO and msxml) • Access to COM libraries incurs interop boundary crossing – Convert existing ASP pages to ASP.NET with new libraries (ADO.NET and System.XML)

Converting ASP pages to ASP.NET

Some pages can be converted by simply renaming to .aspx

Most pages will need some 'touch up' – Many directives have been changed (or removed) – VBScript is not directly supported (must be VB.NET) – COM object interaction may require ASPCOMPAT mode – Code block placement different in ASP.NET

Updating directives from ASP >ASP.NET

Several directives in ASP are no longer supported – <% option explicit %> – <%@ language="vbscript" %> Instead, use equivalent ASP.NET directives/attributes – <%@ Page Language="VB" Explicit="true" %>

Not VBScript = VB.NET

Many language changes mean VBScript code needs to be updated – VB.NET doesn't support default properties •

objRS("au_fname") => objRS.Fields("au_fname")

– IsNull won't work when testing DB results •

IsNull(dbField) => IsDBNull(dbField)

– Let and Set are no longer supported •

Set obj = CreateObject("xx") =>

•

obj = CreateObject("xx")

Not VBScript = VB.NET

– Date() is no longer an expression (it is a type) •

Date() => DateTime.Now

– Parameters must be passed within parentheses •

Response.Write "hi" => Response.Write("hi")

Interacting with COM

By default, ASP.NET applications will run in an MTA thread when accessing COM objects through interop – Many classic ASP components are STA-threaded which means that all calls incur a thread-switch – Avoid this by using the AspCompat attribute –

<%@ Page AspCompat="true" %>

Summary

ASP.NET is an evolution of dynamic web page generation techniques All pages in ASP.NET are compiled assemblies Code-behind is a useful technique for separating code logic from presentation Shadow copying enables 'xcopy' deployment Migrating ASP applications typically requires some explicit conversion on your part