Delegate Controls in SharePoint is a blessing when you are customizing the features and interface of SharePoint. The Delegate Controls are areas in the out-of-the-box SharePoint pages where you are allowed to inject your own controls. This is heavily used by Microsoft Office SharePoint Server 2007, which essentially is a set of features on top of Windows SharePoint Services. For example the standard WSS user information page redirects to the MOSS My Site, this redirection is done by inserting a delegate control into a specific delegate control on the userdisp.aspx page. This nifty delegate control can be used in a WSS solution when you want to create a custom profile page, without modifying any of the OOB files and easily reverts to it’s original state when you deactivate the feature.
Read more about Delegate Controls here.
There are several places where you can inject your own code, and very few of them are documented, hence this blog post, which has lived as a OneNote page for me for some time. This is not a complete reference, but contains the most important (imho) delegate controls.
AdditionalPageHead (allows multiple)
Exists in all the default master pages and allows you to insert controls in the head element of the page.
The search input box present on all pages. WSS automatically adds the searcharea.ascx control here. MOSS replaces this one with the MOSS Search input box
Exists in the default.master. MOSS uses this one to publish the variations menu
Exists in the default.master. MOSS uses this one to add the link to My Site
Exists in the default.master. MOSS uses this one to publish the My Links feature
Used in Central Admin by MOSS. Located in the top of the Quick Launch
Exists on the create site collection page and used by MOSS to insert the categorization of Site Collections.
Same as above but when creating Sites
Exists on the userdisp.aspx page. MOSS uses this one to redirect user the the MySite.
Do you have any favorite Delegate Controls?