For example, a web page that uses a theme setting to control look-and-feel.  If the user has selected their own theme then use that; otherwise use the site’s default theme; or, if that’s not defined, use the global theme; or finally if no global theme is defined then fall back to a system default.

The long, readable version

Using good, old fashioned, conditional logic.

string theme;
if (userTheme != null)
{
    theme = userTheme;
}
else if (siteTheme != null)
{
    theme = siteTheme;
}
else if (globalTheme != null)
{
    theme = globalTheme;
}
else
{
    theme = defaultTheme;
}

The shorter, slightly befuddling version

By nesting the ternary conditional operator in a most disagreeable way.

string theme =
    userTheme != null ? userTheme
    : siteTheme != null ? siteTheme
    : globalTheme != null ? globalTheme
    : defaultTheme;

The deluxe C# 3.0 version

With the overkill of an implicitly-typed array, an IEnumerable extension method, and a lambda predicate.

string theme = new [] {
    userTheme, siteTheme, globalTheme, defaultTheme
}.First(t => t != null);

The elegant coalescence version

With C# 2.0’s null-coalescing operator, doing what it does best.

string theme = userTheme ?? siteTheme ?? globalTheme ?? defaultTheme;

• 70-515 TS: Web Applications Development with Microsoft® .NET Framework 4
• 70-516 TS: Accessing Data with Microsoft® .NET Framework 4
• 70-513 TS: Windows Communication Foundation Development with Microsoft® .NET Framework 4
• 70-519 Pro: Designing and Developing Web Applications using Microsoft® .NET Framework 4

More info on Gerry O’Brien’s blog here: Free Certification Exams

Table table = new Table()
{
    Rows =
    {
        new TableRow()
        {
            Cells =
            {
                new TableHeaderCell()
                    { Scope = TableHeaderScope.Column, Text = "MyColumn" }
            }
        }
    }
};

Then the rendered HTML won’t be W3C compliant because a scope value of “column” isn’t valid:

<table border="0">
    <tr>
        <th scope="column"></th>
    </tr>
</table>

According to the W3C HTML and XHTML specs, the acceptable values for scope are [row|col|rowgroup|colgroup]. This is confirmed by the W3C Markup Validation Service, which reports the error:

Stepping into the source code for the TableHeaderCell control with Reflector or the .NET Reference Source, you can see the root of the problem:

protected override void AddAttributesToRender(HtmlTextWriter writer)
{
    TableHeaderScope scope = Scope;

    if (scope != TableHeaderScope.NotSet)
    {
        writer.AddAttribute(HtmlTextWriterAttribute.Scope,
            scope.ToString().ToLowerInvariant());
    }
}

When the control sets the scope attribute’s value, it uses a lowercase string representation of the TableHeaderScope.Column enumeration, i.e. “column”. An enum value of TableHeaderScope.Col would’ve been ok, but TableHeaderScope.Column is invalid.

Workarounds

Neil has a good workaround by adding the scope attribute manually instead of using the TableHeaderCell.Scope property:

TableHeaderCell th = new TableHeaderCell();
th.Attributes["scope"] = "col";

I thought I’d have a go at extending this fix into a simple control adatper that makes sure TableHeaderCell always renders itself correctly. It works by checking whether the Scope property is set to TableHeaderScope.Column, and if so manually adds the attribute scope=”col” instead. Here’s the code:

    public class TableHeaderCellAdapter : WebControlAdapter
    {
        protected override void RenderBeginTag(HtmlTextWriter writer)
        {
            TableHeaderCell th = (TableHeaderCell) this.Control;

            if (th.Scope == TableHeaderScope.Column)
            {
                th.Scope = TableHeaderScope.NotSet;
                th.Attributes["scope"] = "col";
            }

            base.RenderBeginTag(writer);
        }
    }

To associate the control adapter class with the TableHeaderCell control, add a browser definition file to the App_Browsers folder:

    <!-- file: ~/App_Browsers/ControlAdapters.browser -->
    <browsers>
        <browser refID="Default">
            <controlAdapters>
                <adapter
                  controlType="System.Web.UI.WebControls.TableHeaderCell"
                  adapterType="TableHeaderCellAdapter" />
            </controlAdapters>
        </browser>
    </browsers>

Control Panel – Programs – Turn Windows features on or off

Then find the Intenet Information Services section and add everything you need, including ASP.NET.

• SqlMembershipProvider – managing user credentials and authentication
• SqlRoleProvider – handling role-based authorisation
• SqlProfileProvider – storing and retrieving information about individual users
• SqlPersonalizationProvider – saving state of web parts
• SqlWebEventProvider – capturing and logging web event data

ASP.NET SQL Server Registration Tool

Adding support for these providers to your database is easy, just run the ASP.NET SQL Server Registration tool from the command-line (aspnet_regsql.exe) to launch the ASP.NET SQL Server Setup Wizard.  This will guide you through the process with a simple GUI:

cd C:\Windows\Microsoft.NET\Framework\v2.0.50727 aspnet_regsql.exe

By default, the wizard installs all five services : Membership, Roles, Profiles, Personalization and Web Events. However, if you need support for only some, say just Membership and Roles, then aspnet_regsql can be run from the command-line with specific options, for example:

 aspnet_regsql -S MySqlServer -E -A mr -d MyAspDatabase

This installs the Membership and Roles services (-A mr) on server MySqlServer in database MyAspDatabase using current Windows credentials for authentication.  To see a full list of command-line options and switches, run the registration tool with the help flag:

 aspnet_regsql.exe /?

There’s also an option to generate just SQL scripts without executing them, and another to remove services from the database that aren’t used or needed anymore. (You can also manage SQL cache dependencies and session state using this tool.)

For more info about ASP.NET SQL providers:

• MSDN – ASP.NET Provider Model (PDF)
• Video – How Do I: Set Up the SQL Membership Provider
• Configuring ASP.NET 2.0 Application Services to use SQL Server 2000 or SQL Server 2005
• Examining ASP.NET 2.0’s Membership, Roles, and Profile

That freakish Frankenstein waterfall horse is going to give me nightmares.

Subjects covered are:

• Parallelism
• ADO.NET Data Services
• F#
• Office Programmability
• ASP.NET AJAX
• ASP.NET MVC
• ASP.NET WebForms
• Managed Languages

And there’s even more ASP.NET 4.0 training in the ASP.NET 4.0 Quick Hit Videos series.  A great introduction to loads of new features in bite-size pieces:

• Chart Control
• Dynamic Metadata
• Permanent Redirect
• Imperative WebForms Routing
• Declarative WebForms Routing
• Outbound WebForms Routing
• Auto Start
• Clean Web.Config Files
• Predictable Client IDs
• Selective View State
• The HtmlEncoder Utility Method
• New Rendering Option for Check Box Lists and Radio Button Lists
• Persistent GridView Row Selection
• Table Free Templated Controls
• Easy State Compression
• Tableless Menu Control
• Imperative JavaScript Syntax for Microsoft Client Side Controls
• The ScriptLoader
• jQuery Syntax for Microsoft Ajax
• AJAX Data Templates
• Hidden Field Divs
• Disabled Control Styling

For simple variations you can use separate configuration settings for each country. For example, a regular expression in web.config to validate a local telephone number. But if the logic is more complex then you might need a different plan.

An obvious approach is to use conditional switch/select-case statements, like this:

switch (countryCode)
{
   case "FR":
   /* Logic for France */
   case "US":
   /* Logic for USA */
}

But for large applications this can quickly get unwieldy and difficult to manage. Adding a new country means finding every switch statement and adding a new case.

Instead, a good solution is the Factory Method design pattern. It makes your application much easier to maintain, and adding new countries is easy. Here’s a quick example that extends the idea of validating local postcode formats.

Class Diagram

These are the classes used, described below in more detail.

Step 1

Create an abstract class for performing local validation called LocalValidatorBase. This is a base class which can’t be instantiated. Add a method signature IsValidPostcode that takes a string and returns a boolean. Classes for various countries can now derive from LocalValidatorBase and override IsValidPoscode with custom validation logic.

(The LocalValidatorBase class can contain logic to share between all the subclasses, but if this isn’t necessary then you can create an interface instead of an abstract class called something like ILocalValidator.)

Step 2

Derive two local validation classes from LocalValidationBase called LocalValidatorAU and LocalValidatorDE, one for Australia and one for Germany. In each, override IsValidPoscode to perform country-specific logic for validating a postcode, maybe by checking the string length or matching against a regular expression. The details aren’t important here.

Step 3

Create a factory class to return the correct validator object for the current country setting. Add a static/shared factory method called GetLocalValidator that returns a LocalValidatorBase class. The magic of polymorphism means this method can return any class derived from LocalValidatorBase. Use a switch statement, or some other conditional logic, to return a new instance of LocalValidatorDE or LocalValidatorAU depending on a country code parameter or the thread’s current culture name.

Step 4

That’s all there is to it. You can now call the factory method to get the correct validator object for the current country.

' call the factory method to get a concrete validator
Dim validator As LocalValidatorBase = _
  LocalValidatorFactory.GetLocalValidator()

Dim isValid As Boolean = validator.IsValidPostcode("12345")

The validation success depends on the rules in the object returned by GetLocalValidator, which will be different depending on the current country.

• Inspect and edit live HTML and CSS
• Visualise CSS box-model
• Monitor network metrics
• Debug and profile JavaScript
• DOM explorer

Exam 70–528: .NET 2.0 Web-Based Client Development

• Microsoft Preparation Guide
• Web-based Client Development – Free Skills Assessment
• MeasureUp practice test (150 questions)
• Wikibook MCTS textbook

Exam 70–536: .NET 2.0 Application Development Foundation

• Microsoft Preparation Guide
• MeasureUp practice test (150 questions)
• MCTS 70-536 Exam Prep (book)
• Exam syllabus with MSDN links
• C# Online.NET Study Guide