Control Adapters

Had my first run it with ASP.Net control adapters this week. I was using the built in Menu control which was unfortunately rendering as a table. I needed a menu that rendered as a list using <li> tags instead.

Up to the plate stepped control adapters. These let you mess with the presentation layer of the control, in this case change a menu from rendering <Table> tags to <li>.

Here's how...

Add a App_Browsers folder to the project, you can do this from the right click menu.
Add in a "Form.browser" file. This is an XML file that tells the ASP system what class to use instead of the menus presentation layer. Here's a sample.

<browsers>
<browser refID="Default">
<controlAdapters>
<adapter controlType="System.Web.UI.WebControls.Menu" adapterType="TDWeb.MenuControlAdapter" />
</controlAdapters>
</browser>
</browsers>

The "TDWeb.MenuControlAdapter" is the Namespace and class name.

namespace TDWeb {

 #region Namespace references

 using System;
 using System.Web.UI;
 using System.Web.UI.Adapters;
 using System.Web.UI.WebControls;
 using System.Web.UI.WebControls.Adapters;


 #endregion

 public class MenuControlAdapter : MenuAdapter {

  #region Methods

  private bool MenuItemContainsSelectedItem(MenuItem menuItem) {

   if ( menuItem.Selected )
    return true;

   foreach ( MenuItem childItem in menuItem.ChildItems ) {

    if ( this.MenuItemContainsSelectedItem(childItem) ) {
     return true;
    }

   }

   return false;

  }

  protected override void OnPreRender(EventArgs e) {
   base.OnPreRender(e);

   if ( this.Control != null ) {

    this.SelectCurrentPage(this.Control.Items);

   }

  }

  protected override void RenderContents(HtmlTextWriter writer) {

   if ( this.Control != null ) {

                writer.AddAttribute(HtmlTextWriterAttribute.Id,"qm0");
                writer.AddAttribute(HtmlTextWriterAttribute.Class,"qmmc");
    writer.RenderBeginTag(HtmlTextWriterTag.Ul);
    foreach ( MenuItem menuItem in this.Control.Items ) {
     this.RenderMenuItem(menuItem, writer, 0, true);
    }
    writer.RenderEndTag();

   }

  }

  private bool RenderMenuItem(MenuItem menuItem, HtmlTextWriter writer, int level, bool withArrows) {

   bool selected = this.MenuItemContainsSelectedItem(menuItem);

   if ( this.Control.StaticDisplayLevels >= level ) {

    // Render each item as a 
 ... 
    //writer.RenderBeginTag(HtmlTextWriterTag.Li);
                writer.Write(@"                if (menuItem.Selected)
                {
                    writer.Write(@" class=""selectedmenuitem"" ");
                    //writer.AddAttribute(HtmlTextWriterAttribute.Class, "selectedmenuitem");
                }
                writer.Write(@">");
    // Current item should be styled with "selected" class ...
                //if ( selected )
                //    writer.AddAttribute(HtmlTextWriterAttribute.Class, @"qmparent");
                    
    // If a description was specified, add it as a tooltip ("title" attribute) ...
    if ( menuItem.ToolTip != string.Empty )
     writer.AddAttribute(HtmlTextWriterAttribute.Title, menuItem.ToolTip);

                
    // Render the "href" attribute ...
    //if ( !menuItem.Selected )
     writer.AddAttribute(HtmlTextWriterAttribute.Href, menuItem.NavigateUrl);
                    
                
                //writer.AddAttribute(HtmlTextWriterAttribute.Class, "selectedmenuitem");

                //// Render the "A" element ...
                //if (level == 0)
                //{
                //    writer.AddAttribute(HtmlTextWriterAttribute.Class, "qmparent");
                //}
    writer.RenderBeginTag(HtmlTextWriterTag.A);
    writer.WriteEncodedText(menuItem.Text);
    writer.RenderEndTag();



                //if ( withArrows )
                //    writer.WriteEncodedText(@" | ");

    // Now render any child items ...
    if ( this.Control.StaticDisplayLevels > level ) {
     if (menuItem.ChildItems.Count > 0 ) {
      writer.RenderBeginTag(HtmlTextWriterTag.Ul);
      foreach ( MenuItem childItem in menuItem.ChildItems ) {
       this.RenderMenuItem(childItem, writer, level + 1, false);
      }
      writer.RenderEndTag();
     }
    }

    // Close the 
 ... 
 tag ...
                writer.Write(@"");
    //writer.RenderEndTag();
   }

   return menuItem.Selected;

  }

  private void SelectCurrentPage(MenuItemCollection menuItems) {

   Uri rawUrl = new Uri(this.Control.Page.Request.Url, this.Control.Page.Request.RawUrl);
   this.SelectCurrentPage(menuItems, rawUrl);

  }

  private void SelectCurrentPage(MenuItemCollection menuItems, Uri rawUrl) {

   foreach ( MenuItem menuItem in menuItems ) {

    string navigateUrl = this.Control.ResolveUrl(menuItem.NavigateUrl);
    Uri targetUrl = new Uri(rawUrl, navigateUrl);
    menuItem.Selected = string.IsNullOrEmpty(menuItem.NavigateUrl = rawUrl.MakeRelativeUri(targetUrl).ToString());

    this.SelectCurrentPage(menuItem.ChildItems, rawUrl);

   }

  }

  #endregion

 }

}