UPDATE dated August 17, 2009

Once I posted this entry, there is a lot of interest that has been shown and few queries as well.  So I thought I need to update this post.

This is only the first post in the series on ASP.NET 4.0 fetaures.  There are lot of ground breaking things and other enhancements that are pretty exciting.

To the folks who asked for "why MS changing dev platform once in 18 months"

There is no change.  there are a few enhancements.  Post .NET 2.0 there have been a lot of additional APIs such as LINQ, Entity Framework etc., which are different ways of data handling.  While core ADO.NET is still valid, these are additional enhancements that can be used at the Developer's / Architect's discretion. 

For the folks you asked about URL Rewriting

There is URL Routing which is much better than URL Rewriting.  We have talked about it, enough in the past .  You can read more about it at http://www.mostlylucid.net/archive/2009/01/25/asp.net-4.0-webform-routing-quick-rsquon-dirty-version.aspx

I will be covering more features in the following post.

Thanks for the inerest

With Visual Studio 2010 Beta 1 and .NET Framework Beta 1 out for some time, this post is due from me for a long time.   ASP.NET 4.0 has many improvements for different set of scenarios such as Webforms, Dynamic Data & AJAX based web development.  There are also a lot of enhancements to the core runtime that powers ASP.NET such as Caching, Session & Request/Response objects.

For this post, we will examine some of the web form enhancements.  There are sure a lot of them and we will examine some of them in the future posts.

Controlling View State using the ViewStateMode Property – Performance Enhancement

One of the most complained thing in ASP.NET Webform is the growing viewstate which becomes a concern for performance.  While earlier you can set the EnableViewState property to true or false, post that, all the controls, by default inherit and even if you set it to enabled at control level, the behaviour was inconsistent.

With ASP.NET 4.0, the ViewStateMode property helps to determine for every control, whether the ViewState should be enabled, disabled or inherited accordingly.  Ex.-

<asp:Panel ID="pnlViewState" runat="server" ViewStateMode="Disabled">
      Disabled: <asp:Label ID="label1" runat="server"  Text="Value set in markup" ViewStateMode="Inherit"  /><br />
           Enabled: <asp:Label ID="label2"  runat="server" Text="Value set in markup" ViewStateMode="Enabled" />
  <hr />
  <asp:button ID="Button1" runat="server"  Text="Postback" />
    </asp:Panel>

In the code-behind

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            label1.Text = "Value set in code behind";
            label2.Text = "Value set in code behind";
        }
    }

When you run the above page, you can find that the intial value for both the labels is set to “Value set in code behind” whereas after clicking on the button (postback), the value of label1 changes to “Value set in markup” whereas the value of label2 remains unchanged.  As you can see, the Panel which holds both these lables has ViewStateMode set to Disabled and label1 is inherting the mode (this is the default if not specified) and label2 has it enabled.  That is the reason label2 maintains viewstate while label1 loses it.

While it is arguably possible using the simple EnableViewState property earlier, it was never consistent.  Considering the fact that in most of our performance sessions, we talk about disabling viewstate and then enabling it at control level while it doesnt work, this ViewStateMode is a welcome architectural change to improve performance.

Page Meta Keyword & Description – Search Engine Optimization feature

Upto Visual Studio 2008, one can set the Title of the page declaratively or through program using Page.Title.  However, as more and more web traffic is happening through search engines, Page’s Title, Keyword and description become more important.  Although the Keyword feature was exploited and hence many search engines today ignore it, Page Description is something still major search engines such as Google, Bing use for identifying and indexing pages based on content.

The new feature in ASP.NET 4.0 allows users to programmatically set the Page Description and Keywords as follows:-

protected void Page_Load(object sender, EventArgs e)
    {
        this.Page.Title = "My ASP.NET Blog";
        this.Page.MetaKeywords = "ASP.NET, Web Development, Blog, ASP.NET Blog";
        this.Page.MetaDescription = "This Blog contains posts related to ASP.NET and Web Development";
    }

The above code appends the following markup

<meta name="keywords" content="ASP.NET, Web Development, Blog, ASP.NET Blog" />

<meta name="description" content="This Blog contains posts related to ASP.NET and Web Development" />

And the way it works is that, if the meta tags are already present in the HTML markup, whatever is set in the code behind  will fill up the “content” part alone if the “name” tag is matching.

Although this looks simple, it is very useful in cases where you want to set these dynamically based on a condition / criteria.  So far, these were set statically in the HTML.  Now with Page Class level access, these can be set dynamically.

There are many more enhancements to Webforms such as Routing improvements, setting ClientID etc., which we will examine in the future posts.

Cheers !!!