Damo's spot on the web

I haven't posted here in a long time so I thought I'd do a quick heads up of what I've been doing lately:

• I received an MVP award from Microsoft in ASP/ASP.NET.
• I passed a couple more MS exams to complete my MCSD.NET. This leaves me only one MS exam off of finishing my Masters degree.
• I bought an iPhone 3G.
• I published my first iPhone web app. It's an online connection speed test: http://www.iphonespeedcheck.com
• I hosted another meeting of the Ballarat.NET SIG. We were lucky enough to have two great presenters in Mahesh Krishnan and Tatham Oddie. Thanks again to Command Centre Ballarat for providing us with the venue. (if you're interested in presenting at future Ballarat.NET SIG events I'm always looking for presenters so please drop me a line via email, facebook, twitter, messenger, etc.)

On top of that I finished up a long term gig I'd been on and took a couple of weeks off to unwind.

What's on my radar for the coming months?

• Presenting the session Lachlan Hardy and I did at ReMIX this year on Internet Explorer 8 at the RDN events in Sydney and Melbourne.
• I'm helping to organise and coordinate the Chalk Talks at this year's Tech.Ed in Sydney (more details on this soon).
• Check out Web Directions South in Sydney.
• Do some further updates to www.iphonespeedcheck.com
• Explore the new features in ASP.NET AJAX 4.
• Add some new features to the AccessKeyHighlighter AJAX control.
• Record some screencasts on the AccessKeyHighlighter and ASP.NET AJAX 4.
• Participate in the Internet Explorer 8 Beta 2 Feedback and generally checking out what it has to offer.
• Look into completing the requirements to become a Microsoft Certified Trainer.
• Build a new developer workstation for home.

Phew, that looks like enough! If you want to know what I'm thinking at any given time I can usually be heard chirping over on Twitter.

I've released an update to the AccessKeyHighlighter to resolve a couple of issues and add some new features. Check it out on its CodePlex page.

I've finally managed to get the first release of my AccessKeyHighlighter control for ASP.NET AJAX published. When the control is placed on a form it highlights the access keys assigned to form fields when the user holds down the access key shortcut key in their browser (Alt for IE & Safari, Shift+Alt for Firefox). You can see a live demo of it in action here.

If you find it useful, be sure to leave me a note on the CodePlex site, and if you find any issues or have any suggestions for improvements or new features, please create a feature request on the Issue Tracker page.

Thanks to all those who attended my and Lachlan's session on IE8 at ReMIX in Sydney and Melbourne. We hope you got something out of it. You can download the deck and demo from the session below.

• ReMIX Welcome to Internet Explorer 8: PowerPoint slide deck
• ReMIX Welcome to Internet Explorer 8: Demos

People who know me will know that I love CSS and that I can often be found with my head deep in a CSS file in Visual Web Developer (the web tools in Visual Studio). Recently I've been thinking about how Microsoft could make the support for editing CSS files directly in these tools more conducive to discovering features of CSS you don't know about, improving productivity through better contextual awareness, and offering insight as to real world issues such as browser compatibilities.

So I've put together a series of mock-ups that illustrate some of the ideas I have for improving the support for CSS file editing:

• Inline RGB colour picker
• Ability to define colour swatches in XML comments including name, RGB and category
• Inline colour swatch picker with $ keyboard shortcut that replaces name with hex RGB value on completion
• Inline named colour picker with preview of named colour in pick list
• Ability to choose browsers to warn of incompatibilities with when schema checking CSS
• Green "squigglies" under CSS selectors and properties know to be unsupported or have issues in chosen warning browsers
• ToolTips for CSS properties showing description and browser compatibility summary with hyperlinks to further information
• ToolTips for CSS selectors showing description of what elements it will select, browser compatibility summary and specificity score with hyperlinks to further information on each
• ToolTip preview of url resources (images) showing file size and image dimensions
• ToolTip preview of font-family showing font source (TrueType, W3C, etc.) and font rendering preview
• Support for automatic indenting of style declarations based on descendant or child selectors if they appear after each other

Hopefully somebody on the appropriate teams in Microsoft will here me :)

This week I'm presenting at ReMIX Australia in Sydney (yesterday) and Melbourne (tomorrow). I'm presenting a session along with Lachlan Hardy on Internet Explorer 8. The talk focuses heavily on web standards as that is the big news for IE8. Hope to see you there.

You might find that when you add the meta tag required to force IE8 beta 1 into IE7 (or 6) rendering mode into your ASP.NET page (or Master Page) that it doesn't work as expected.... IE8 continues to render the site in full standards mode. The reason might be that in beta 1 of IE8 the "X-UA-Compatible" meta tag must be the first element in the page head element and by default ASP.NET will insert the link tags to the CSS files in your theme at the beginning of the head element of your page (or Master Page), before any other elements that might actually be defined in the .aspx or .master file.

To fix this, add the following code to the page's (or Master Page's) PreRender event handler (Page_PreRender):

// Move browser tageting meta tag to top of header
HtmlMeta meta = null;
int metaXUACompatIndex = -1;
foreach (Control ctl in page.Header.Controls)
{
    meta = ctl as HtmlMeta;
    if (meta == null)
        continue;

    if (meta.HttpEquiv == "X-UA-Compatible")
    {
        // Grab index
        metaXUACompatIndex = page.Header.Controls.IndexOf(meta);
        break;
    }
}
if (metaXUACompatIndex > 0)
{
    HtmlMeta metaXUACompat = page.Header.Controls[metaXUACompatIndex] as HtmlMeta;
    page.Header.Controls.RemoveAt(metaXUACompatIndex);
    page.Header.Controls.AddAt(0, metaXUACompat);
}

This will move the browser targeting meta tag to the top of the list so that IE8 will honour it.

Keep track of what I'm doing (when I have charge) on twitter: http://twitter.com/DamianEdwards

ASP.NET includes a feature called "Themes" that allows you to organise styling artifacts including CSS stylesheets and images into logical units that can be easily applied to a page or entire site through configuration. Part of this feature is the ability to create .skin files that set default values for certain properties of ASP.NET server controls as part of a theme.

Not all properties of ASP.NET controls are skinnable. Indeed the initial intention of .skin files was to enable the setting of default values for properties such as FontColor and BorderWidth, which when serving to CSS supporting browsers ASP.NET will render as inline style attributes on the emitted HTML controls. So what place do they have when we apply all of our style rules via way of attached CSS stylesheets and selectors (the way we should)?

Despite their evil initial purpose we can put .skin files to good use for two purposes:

1. Assigning CSS classes to all instances of particular ASP.NET server controls; and
2. Zeroing out the default inline style that ASP.NET sets on some controls.

So how does this work?

In your theme folder add a new .skin file called Controls.skin:

Now we want to add some declarations to the file to:

1. Zero out the inline style of the ASP.NET validator controls; and
2. Assign a default CSS class name to the Button, LinkButton, TextBox and validator controls.

<asp:RequiredFieldValidator runat="server" ForeColor="" CssClass="validation-error" />
<asp:RangeValidator runat="server" ForeColor="" CssClass="validation-error" />
<asp:CompareValidator runat="server" ForeColor="" CssClass="validation-error" />
<asp:RegularExpressionValidator runat="server" ForeColor="" CssClass="validation-error" />
<asp:CustomValidator runat="server" ForeColor="" CssClass="validation-error" />

<asp:LinkButton runat="server" CssClass="button" />
<asp:Button runat="server" CssClass="button" />
<asp:TextBox runat="server" CssClass="text-box" />

And that's it! Now when ASP.NET renders these controls when they appear on a page (or in a site) with your theme configured, they'll automatically pick up properties defined in this .skin file.

In my recent RDN presentation on CSS Layout with ASP.NET & Visual Studio 2008 I mentioned a technique I use to get some extra value from the ObjectDataSource control. From speaking with other developers I've found that many people try to use the control only to be dissatisfied with the way it works, and in particular the need to provide it with a separate business logic or gateway class to look for its CRUD methods on. This is most apparent when you are trying to separate the data-access, business and presentation logic through way of a MVC or MVP pattern like "Passive View". In this scenario most people go back to the method of setting the DataSource property of their data bound control directly and manually calling the DataBind() method. This is a shame as it prevents you from realising the productivity gains and ease of maintenance of the no-code support for paging and sorting when using a data source control (plus the ability to fully style the GridView as described in my previous article).

Rather than abandoning the ObjectDataSource altogether, we can make it work for us, by sub-classing it and changing it's behaviour slightly so that it looks for its methods on the hosting page or user control instead, i.e. its parent in the control hierarchy.

(If you have never looked at the data-source controls and two-way data-binding support in ASP.NET 2.0 before, it might be worth first checking out Scott Mitchell's excellent tutorials on the subject.)

Start out by adding a new class to your project called ParentDataSource.cs. I like to put all custom and user controls in a Controls sub-folder and thus namespace.

Make this new class inherit from the ObjectDataSource class and a ToolboxData attribute to define its tag name (you'll need to add some using statements to import the appropriate namespaces too):

namespace RDN.CSSReadiDepth.Controls
{
    [ToolboxData("<{0}:ParentDataSource runat=server></{0}:ParentDataSource>")]
    public class ParentDataSource : ObjectDataSource
    {

Now add a couple of constructors. These do a few things. First they enable paging and sorting by default (you don't need to do this but I use paging and sorting more often than not). Secondly they wire-up some events of the control to local handler methods:

public ParentDataSource()
    : this(String.Empty, String.Empty)
{ }

public ParentDataSource(string typeName, string selectMethod)
    : base(typeName, selectMethod)
{
    this.EnablePaging = true;
    this.SortParameterName = "sortExpression";

    this.Init += new EventHandler(ParentDataSource_Init);
    this.ObjectCreating += new ObjectDataSourceObjectEventHandler(ParentDataSource_ObjectCreating);
    this.ObjectDisposing += new ObjectDataSourceDisposingEventHandler(ParentDataSource_ObjectDisposing);
}

Now we need to add our event handler methods. They're going to do the following:

• Init handler: walk the control tree to find the page or user control the data source is being hosted on and then set the TypeName property to the type of the hosting page or user control;
• ObjectCreating handler: set the instance of the object we want our data source control to bind to, which will be the page or user control it is hosted on; and
• ObjectDisposing handler: cancel the default behaviour of the ObjectDataSource which is to dispose of the object it is bound to.

void ParentDataSource_Init(object sender, EventArgs e)
{
#if DEBUG
    System.Diagnostics.Stopwatch sw = new System.Diagnostics.Stopwatch();
    sw.Start();
#endif
    FindParentHost(this);
#if DEBUG
    sw.Stop();
    System.Diagnostics.Debug.WriteLine(String.Format("Finding parent host for data source took {0}", sw.Elapsed));
#endif
}

void ParentDataSource_ObjectCreating(object sender, ObjectDataSourceEventArgs e)
{
    e.ObjectInstance = _parentHost;
}

void ParentDataSource_ObjectDisposing(object sender, ObjectDataSourceDisposingEventArgs e)
{
    e.Cancel = true;
}

Note I've also included some timing code in the Init handler so you can measure the impact of this method (it's negligible).

Finally we need to add some private members to support the handler methods:

Object _parentHost;

/// <summary>
/// Walks the control tree to find the hosting parent page or user control
/// </summary>
/// <param name="ctl">The control to start the tree walk at</param>
private void FindParentHost(Control ctl)
{
    if (ctl.Parent == null)
    {
        // User control was not found, use page base type instead
        this.TypeName = this.Page.GetType().BaseType.FullName;
        _parentHost = this.Page;
        return;
    }

    // Find the user control base type
    UserControl parentUC = ctl.Parent as UserControl;
    MasterPage parentMP = ctl.Parent as MasterPage;
    if (parentUC != null && parentMP == null)
    {
        Type parentBaseType = ctl.Parent.GetType().BaseType;
        this.TypeName = parentBaseType.FullName;
        _parentHost = ctl.Parent;
        return;
    }
    else
    {
        FindParentHost(ctl.Parent);
    }
}

The method FindParentHost, walks the control tree from the data source control until it finds the user control it is hosted on. If it can't find a hosting user control it assumes the control is hosted on a page. Once it finds the host it sets the TypeName property accordingly (note that the MasterPage class actually inherits from UserControl so we explicitly exclude that case).

Now that we have our customised data source control it's time to use it in anger! Add a declaration to the web.config to import the controls from the DLL containing the ParentDataSource control:

<pages styleSheetTheme="Theme1">
  <controls>
    <add tagPrefix="cc" namespace="RDN.CSSReadiDepth.Controls" assembly="RDN.CSSReadiDepth" />
  </controls>
</pages>

Now you can place the control in your page or user control mark-up file (.aspx or .ascx) and set the DataSourceID of your data-binding target control:

<asp:GridView ID="gvExample" runat="server" DataSourceID="pdsExample" DataKeyNames="Id"
    AllowPaging="true" AllowSorting="true" PageSize="10" AutoGenerateColumns="false"
    CssClass="customers-grid">
    <Columns>
        <asp:BoundField HeaderText="First Name" DataField="FirstName" SortExpression="FirstName"
            HeaderStyle-CssClass="first-name" ItemStyle-CssClass="first-name"
            AccessibleHeaderText="The customer's first name" />
        <asp:BoundField HeaderText="Last Name" DataField="LastName" SortExpression="LastName"
            HeaderStyle-CssClass="last-name" ItemStyle-CssClass="last-name"
            AccessibleHeaderText="The customer's last name" />
        <asp:BoundField HeaderText="Age" DataField="Age" SortExpression="Age"
            HeaderStyle-CssClass="age" ItemStyle-CssClass="age"
            AccessibleHeaderText="The age of the customer" />
        <asp:BoundField HeaderText="Member for" DataField="YearsAsMember" SortExpression="YearsAsMember"
            HeaderStyle-CssClass="years-as-member" ItemStyle-CssClass="years-as-member"
            AccessibleHeaderText="How many years the customer has been a member for" />
    </Columns>
</asp:GridView>
<cc:ParentDataSource ID="pdsExample" runat="server"
    SelectMethod="GetData" SelectCountMethod="GetDataRowCount" />

In this example I need to implement two methods on my page's code-behind file: GetData and GetDataRowCount. The first gets the current page of data to display, the second gets the total number of records (this is needed so the data source controls can calculate paging information):

#region << Data Binding Methods >>

public IEnumerable<Customer> GetData(string sortExpression, int maximumRows, int startRowIndex)
{
    if (this.Customers == null || this.Customers.Count == 0)
        return this.Customers;

    var sortFunc = this.Customers[0].GetPropertySelector<Customer, object>(sortExpression.Replace(" DESC", ""));

    if (sortExpression.ToUpper().IndexOf(" DESC") >= 0)
    {
        return this.Customers
                // Sort descending
                .OrderByDescending(sortFunc)
                // Grab a single page of data
                .Skip((startRowIndex / maximumRows) * maximumRows)
                .Take(maximumRows);
    }
    else
    {
        return this.Customers
                // Sort ascending
                .OrderBy(sortFunc)
                // Grab a single page of data
                .Skip((startRowIndex / maximumRows) * maximumRows)
                .Take(maximumRows);
    }
}

public int GetDataRowCount()
{
    return (this.Customers != null ? this.Customers.Count : 0);
}

#endregion

In this example the data is stored in a property on the page class itself and I'm using LINQ to simulate sorting and paging. The property is just wrapping calls into the application's session state. The data itself was loaded into session state when the application started up. In a real world example these calls might look up the data from a web-service or database, return data from cache, or in the MVP scenario first raise an event that the presenter class will handle and then return the value of a property on the page (who's contents was set by the event handler in the presenter class). Also, because these methods are instance methods on the actual page object you are free to manipulate other controls or properties of the page class.

You can use this method equally well with any of the ASP.NET controls that support the data source controls, such as GridView, DetailsView, FormView and Repeater. It also works with two-way data-binding.

Download the sample solution used in this article here