Core ASP.NET

By Holger Schwichtenberg

ABOUT ASP.NEt

ASP.NET stands for “Active Server Pages .NET”, however the full name is rarely used. ASP.NET is a framework for the development of dynamic websites and web services. It is based on the Microsoft .NET Framework and has been part of .NET since Version 1.0 was released in January 2002. The current version named 3.5 Service Pack 1 was released in August 2008. The next version, 4.0, is expected to be released at the end of the year 2009.

This Refcard summarizes the most commonly used core functions of ASP.NET. You will find this Refcard useful for some of the most common tasks with ASP.NET, regardless of the version you are using

Instalation

The best development environment for ASP.NET is Microsoft’s Visual Studio. You can either use the free Visual Web Developer Express Edition (http://www.microsoft.com/express/ vwd/) or any of the commercial editions of Visual Studio (e.g. Visual Studio Professional). The latest version that supports ASP.NET 2.0 and ASP.NET 3.5 is “2008” (internal version: 9.0). The .NET Framework and ASP.NET are part of the setup of Visual Web Developer Express Edition and Visual Studio. However, make sure you install Service Pack 1 for Visual Studio 2008, as this will not only fix some bugs but also add a lot of new features.

ASP.NET needs a server with the HTTP protocol (web server) to run. Visual Web Developer Express 2005/2008 and Visual Studio 2005/2008 contain a webserver for local use on your development machine. The “ASP.NET Development Server” (ADS) will be used when specifying a “File System” location when creating your project. Thus, “HTTP” would mean you address a local or remote instance of Internet Information Server (IIS) or any other ASP.NET enabled web server. ADS is a lightweight server that cannot be reached from other systems. However, there are differences between ADS and IIS, especially in the security model that makes it sometimes hard for beginners to deploy a website to the IIS that was developed with ADS. On the production system you will use IIS and only install the .NET Framework, because Visual Studio is not required here.

ASP.NEt Web Applications

An ASP.NET application consists of several .aspx files. An .aspx file can contain HTML markup and special ASP.NET markup (called Web Controls) as well as the code (Single Page Model). However, the Code Behind Model which comes with a separate code file called, the “Code Behind File” (.aspx. cs or .aspx.vb), provides a cleaner architecture and better collaboration between Web designers and Web developers. ASP.NET applications may contain several other elements such as configuration files (maximum one per folder), a global application file (only one per web application), web services, data files, media files and additional code files.

There are two types of Web projects: “Website Projects” (File/ New/Web Site) and “Web Application Projects” (File/New/ Project/Web Application). “Website” is the newer model, while Web Application Projects mainly exist for compatibility with Visual Studio .NET 2002 and 2003. This Refcard will only cover Web Site Projects. Most of this content is also valid for Web Applications.

Figure 1: The Content of an ASP.NET Web Application

The ASP.NET Web form Model

ASP.NET uses an object- and event-oriented model for web pages. The ASP.NET Page Framework analyzes all incoming requests as well as the .aspx page that the request is aimed at. The Page Framework creates an object model (alias control tree) based on this information and also fires a series of events. Event handlers in your code can access data, call external code in referenced .NET assemblies and manipulate the object model (e.g. fill a listbox or change the color of a textbox). After all event handlers have executed, the Page Framework renders the current state of the object model into HTML tags with optional CSS formatting, JavaScript code and state information (e.g. hidden fields or cookies). After interacting with the page, the user can issue a new request by clicking a button or a link that will restart the whole process.

Figure 2: The ASP.NET request/response life cycle

Web Controls

An ASP.NET page can contain common HTML markup. However, only ASP.NET web controls provide full objectand event-based functionality. Web controls have two representations: In the .aspx files they are tags with the prefix “asp:”, e.g. . In the code they are .NET classes, e.g. System.Web.UI.WebControls.TextBox.

Table 1 lists the core members of all web controls that are implemented in the base class “System.Web.UI.WebControls. WebControl”.

Table 1: Core Members in the base class system. Web.UI.WebControls.WebControl.

Tables 2, 3 and 4 list the most commonly used controls for ASP. NET web pages. However, there are more controls included in the .NET platform and many more from third parties not mentioned here.

Table 2: Core controls for ASP.NET web pages.

List controls display several items that the user can choose from. The selectable items are declared static in the .aspx file or created manually using the Items collection or created automatically by using data binding. For data binding you can fill DataSource with any enumerable collection of .NET objects. DataTextField and DataValueField specify which properties of the objects in the collection are used for the list control.

Table 3: List Controls for ASP.NET web pages

Validation Controls check user input. They always refer to one input control ControlToValidate and display a text ErrorMessage if the validation fails. They perform the checks in the browser using JavaScript and also on the server. The client side validation can be disabled by setting EnableClientScript to false. However, the server side validation cannot be disabled for security reasons.

The Page Class

All web pages in ASP.NET are .NET classes that inherit from the base class “System.Web.UI.Page”. The class Page has associations to several other objects such as Server, Request, Response, Application, Session and ViewState (see figure 3). Therefore, developers have access to a wide array of properties, methods and events within their code. Table 5 lists the most important members of a Page and its dependent classes. Please note that the Page class has the class Control in its inheritance hierarchy and therefore shares a lot of members with the WebControl class (e.g. Init(), Load(), Controls, FindControl). However, these members are not repeated here.

Figure 3: Object Model of “System.Web.UI.Page”

Table 5: Most important members of the Page class and its associated classes

A Typical Page

Figure 4 shows the typical content of an .aspx page and Figure 5 the content of a typical code behind class. The sample used is a registration form with three fields: Name, Job Title and Email Address.

<%@ Page Language=”C#” AutoEventWireup=”true”
  CodeFile=”PageName.aspx.cs” Inherits=”PageName” %>
<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Transitional//en”
  “http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd”>
<html xmlns=”http://www.w3.org/1999/xhtml”>
<head runat=”server”>
  <title>Registration Page</title>
  <link href=”MyStyles.css” rel=”stylesheet” type=”text/css”/>
  <style type=”text/css”>
   .Headline
   {
    font-size: large; font-weight: bold;
   }
  </style>
 </head>
 <body>
  <form id=”c_Form” ruanat=”server”>
  <div>
   <asp:Label runat=”server” ID=”C_Headline” Text=”Please register:”
     class=”Headline”></asp:label>
    <p>Name:
   <asp:TextBox ID=”C_Name” runat=”server”></asp:TextBox>
   <asp:RequiredFieldValidator ID=”C_NameVal” ControlToValidate=”C_
   Name” ruanat=”server” ErrorMessage=”Name required”></
   asp:RequiredFieldValidator>
 </p>
    <p>Job Title:
   <asp:DropDownList ID=”C_JobTitle” runat=”server”>
  <asp:ListItem Text=”Software Developer” Value=”SD”></
 asp:ListItem>
  <asp:ListItem Text=”Software Architect” Value=”SA”></
   asp:ListItem>
  </asp:DropDownList>
 </p>
<p>EMail:
  <asp:TextBox ID=”C_EMail” runat=”server”></asp:TextBox>
   <asp:RequiredFieldValidator Id=”C_EMailVal1” ControlToValidate=”C_
  EMail” runat=”server” ErrorMessage=”EMail required”></
  asp:RequiredFieldValidator>
  <asp:RegularExpressionValidator ID=”C_EMailVal2”
 ControlToValidate=”C_EMail” runat=”server” ErrorMessage=”Email
   not valid” ValidationExpression=”\w+([-+.’]\w+)*@\w+([-.]\
     w+)*\.\w+([-.]\w+)*”>
   </asp:RegularExpressionValidator>
   </p>
   <p>
  <asp:Button ID=”C_register” runat=”server” Text=”Register”
 onclick=”C_Register_Click”/>
   </p>
   </div>
 </form>
</body>
</html>

Figure 4: Typical content of an ASPX file

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
public partial class PageName : System.Web.UI.Page
 {
  protected void Page_Load(object sender, EventArgs e)
   {
    // If an authenticated users starts using this page,
    // use his login name in the name textbox
    if (!Page.IsPostBack && Page.User.Identity.IsAuthenticated)
    {
     this.C_Name.Text = Page.User.Identity.Name;
     this.C_Name.Enabled = false;
    }
   }
 protected void C_Register_Click(object sender, EventArgs e)
  {
   if (Page.IsValid) // if all validation controls succedded
   { // call business logic and
    if (BL.Register(this.C_Name.Text, this.C_EMail.Text, this.C_
     JobTitle.SelectedValue))
    { // redirect to confirmation page
     Response.Redirect(“RegistrationConfirmation.aspx”);
    }
    else
    { // change the headline
     this.C_Headline. = “You are already registered!”;
    }
   }
  }
}    

Figure 5: Typical content of a Code Behind file

State Management

State management is a big issue in web applications as the HTTP protocol itself is stateless. There are three standard options for state management: hidden files, URL parameters and cookies. However, ASP.NET has some integrated abstractions from these base mechanisms know as View State, Session State, and Application State. Also, the direct use of cookies is supported in ASP.NET.

The following code snippet shows how to set values for a counter stored in each of these mechanisms:

ViewState[“Counter”] = CurrentCounter_Page + 1;
Session[“Counter”] = CurrentCounter_Session + 1;
Application[“Counter”] = CurrentCounter_Application + 1;
Response.Cookies[“Counter”].Value = (CurrentCounter_User +
  1).ToString();
Response.Cookies[“Counter”].Expires = DateTime.MaxValue; // no
  expiration

Figure 6: Setting Values

The following code snippet shows how to read the current counter value from each of these mechanisms: Next Column ---->

long CurrentCounter_Application, CurrentCounter_ApplicationLimited,
CurrentCounter_Session, CurrentCounter_Page, CurrentCounter_User;
 if (Application[“Counter”] == null) { CurrentCounter_Application =
  0; }
  else { CurrentCounter_Application = Convert.ToInt64(Application[“C
   ounter”]); }
 if (Session[“Counter”] == null) { CurrentCounter_Session = 0; }
  else { CurrentCounter_Session = Convert.
   ToInt64(Session[“Counter”]);}
 if (ViewState[“Counter”] == null) { CurrentCounter_Page = 0; }
  else { CurrentCounter_Page = Convert.
ToInt64(ViewState[“Counter”]); }
 if (Request.Cookies[“Counter”] == null) { CurrentCounter_User = 0; }
  else { CurrentCounter_User = Convert.ToInt64(Request.
   Cookies[“Counter”].Value); }

Figure 7: Reading Values

Configuration

All configurations for ASP.NET applications are stored in XMLbased configuration files with the fixed name “web.config”. In addition to the configuration files in the application root folder, subfolders may also contain a web.config that overrides parent settings. Also, there are the global configuration files machine. config and web.config in the folder \Windows\Microsoft.NET\ Framework\v2.0.50727\CONFIG that provide some default settings for all web applications. (Note: v2.0.50727 is still correct for ASP.NET 3.5!).

Visual Studio and Visual Web Developer create a default root configuration file in your web project that contains a lot of internal setting for ASP.NET 3.5 to work properly. Figure 6 shows a fragment from a web.config file with settings that are often used.

<!-- Connection strings -->
<connectionStrings>
  <add name=”RegistrationDatabase” connectionString=”Data
Source=EO2;Initial Catalog= RegistrationDatabase;Integrated
Security=True” providerName=”System.Data.SqlClient” />
</connectionStrings>
<!-- User defined settings -->
<AppSettings>
  <and key=”WebmasterEMail” value=”hs@IT-Visions.de” />
</appSettings>
<system.web>
  <!-- Specify a login page -->
  <!-- Use the URL for storing the authentication ID if cookies are
not allowed -->
  <!-- Set the authentication timeout to 30 minutes -->
<authentication mode=”Forms”>
  <forms loginUrl=”Login.aspx” cookieless=”AutoDetect” timeout=”30”>
  </forms>
  </authentication>
   <!-- Deny all unauthorizd access to this application -->
  <authorization>
   <deny users=”?” />
  </authorization>
 <!-- Use the URL for storing the session ID if cookies are not
allowed -->
 <!-- Set the session timeout to 30 minutes -->
 <sessionState cookieless=”AutoDetect” timeout=”30”></sessionState>
<!-- Display custom error pages for remote users -->
<customErrors mode=”RemoteOnly” defaultRedirect=”GenericErrorPage.
  htm”>
  <error statusCode=”403” redirect=”NoAccess.htm” />
  <error statusCode=”404” redirect=”FileNotFound.htm” />
</customErrors>
<!-- Turn on debugging -->
<compilation debug=”false”>

Figure 8: Typical setting in the web.config file.

Deployment

ASP.NET applications can be deployed as source code via the so called “XCopy deployment”. This means you copy the whole content of the web project folder to the production system and configure the target folder on the production system as an IIS web application (e.g. using the IIS Manager). The production web server will automatically compile the application during the first request and recompile automatically if any of the source files changed.

However, you can precompile the application into .NET assemblies to improve protection of your intellectual property and increase execution speed for the first user. Precompilation can be performed through Visual Studio/Visual Web developer (Menu “Build/Publish Website”) or the command line tool aspnet_compiler.exe.

About The Author

Holger Schwichtenberg

Holger Schwichtenberg is one of Europe’s best-known experts on .NET and Windows PowerShell. He holds both a Master’s degree and a Ph.D. in business informatics. Microsoft recognizes him as a Most Valuable Professional (MVP) since 2003. He is a .NET Code Wise Member, an MSDN Online Expert and an INETA speaker. He regularly gives high-level talks at conferences such as TechEd, Microsoft Summit, BASTA and IT Forum. He is the CEO of the German based company www.IT-Visions.de that provides consulting and training for many companies throughout Europe.

Publicaitions

Holger Schwichtenberg has published more than twenty books for Addison Wesley and Microsoft Press in Germany, as well as about 400 journal articles. His recent book “Essential PowerShell” has also been published by Addison Wesley in English.

Blog: www.dotnet-doktor.de (German)

Website: www.IT-Visions.de/en

Recommended Book

An in-depth guide to the core features of Web development with ASP.NET, this book goes beyond the fundamentals. It expertly illustrates the intricacies and uses of ASP.NET 3.5 in a single volume. Complete with extensive code samples and code snippets in Microsoft Visual C# 2008, this is the ideal reference for developers who want to learn what s new in ASP.NET 3.5, or for those building professional-level Web development skills.

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