 |
ASP Kitchen |
|
ASP Kitchen |
ASP Kitchen: ASP.NET Articles:
Loading ASP.NET User Controls using the LoadControl Method
Loading ASP.NET User Controls using the LoadControl MethodUser Controls are semi-autonomous pages of HTML and underlying ASP.NET code that can be inserted into ASP.NET pages. As such they are useful for adding blocks of functionality to pages. Typical uses are to use User Controls for page headers and footers. They can also add functionality such as a "property of the week" for a real estate company website. Unlike ASP.NET pages that have the .aspx file extension, User Controls typically have the .ascx file extension. Once created, in Visual Studio.NET they can be included in a specific page by simply dragging the user control onto the design view of that page. Alternatively, they can be added to a page at design time by including the following in the page's HTML. For example, the following line includes a header user control from the HeaderUserControl.ascx file: <%@ Register TagPrefix="uc1" TagName="HeaderUserControl" Src="HeaderUserControl.ascx" %> The header is then positioned on the page using the following tag: <uc1:HeaderUserControl id="Header1" runat="server"></UC1:ADMINHEADER> Although this procedure is satisfactory for content like headers and footers that will always be required on specific pages, it would be useful if there was a way of dynamically loading specific user controls at run time. For example, an online store may only want a "clearance offers" section to appear if there is actually stock inventory in the database that has been marked as being for clearance. Fortunately, it is possible to load user controls onto a page by making use of the <b>LoadControl</b> method. This function has a straightforward syntax - it takes a single argument - the virtual path to the user control page. For example, to load the featured product user control the following C# code would be used within the Page_Load method: Control FeaturedProductUserControl = LoadControl("FeaturedProduct.ascx"); Once the user control has been loaded, it can be added to the page by adding it to the Controls collection: Controls.Add(FeaturedProductUserControl); The drawback with this technique is that it offers no control over where on the page the user control will actually appear. A useful tip is, therefore, to add a PlaceHolder control to the page in the position that you want it to display the dynamically loaded user controls. A PlaceHolder does just that - it acts as a container for other controls. You can then specify that the user control appear within the PlaceHolder by adding the user control to the PlaceHolder's controls collection: PlaceHolderLeftMenu.Controls.Add(FeaturedProductUserControl); Alternatively it is possible to position the user control in other ways, such as adding it to a Panel control: PanelRightMenu.Controls.Add(FeaturedProductUserControl); Making Full Use of Dynamically Loaded User ControlsSince it is possible to dynamically load user controls onto specific pages, it provides the idea functionality for creating page templating facilities within ASP.NET. For example, by storing the details of available user controls in a database, it would be possible to write a content management system that allowed the website's administrative users to choose which user controls they wanted to display on each page. This page templating system is used in content management systems such as the portal layout functionality in Microsoft's SharePoint Portal Server. The ASP.NET IBuySpy sample projects also make use of the LoadControl method to dynamically load content. Useful Development Tools
Author detailsBrett Burridge has worked as a web developer since 1997 and has developed web applications for a range of corporations, start up busiensses and educational establishments. Brett is presently employed as an Internet developer and technical writer through his own company, Winnersh Triangle Web Solutions Limited. The company produces a number of innovative products, including a range of software documentation tools, which include the ASP Documentation Tool™, the .NET Documentation Tool for VB.NET and C#, and the SQL Server Documentation Tool. Other products include The Website Utility, which functions as a website error checker, search engine optimizer and ASP/ASP.NET search engine builder application. As well as the ASPAlliance, Brett has written articles for Ariadne.ac.uk, ASPToday, the software documentation portal www.softwaredocumentation.info, and has contributed recipes to the ASP.NET Developer's Cookbook. links Outside web development, Brett is interested in travelling (here are my travel logs from New York, Hong Kong and Tokyo), digital photography (here's my photo gallery), tropical fishkeeping and collecting contemporary works of art by artists such as Doug Hyde. Contact Brett by emailing
Article history"Loading ASP.NET User Controls using the LoadControl Method" published on ASPAlliance.com on 12 November 2004. ASP Kitchen: ASP.NET Articles: Loading ASP.NET User Controls using the LoadControl Method |
|
||||||||||||||||||||||||
| © page content copyright Brett Burridge 1998 - 2008. | |||||||||||||||||||||||||
