SharePoint Delegate control is a mechanism that we can inject code or a control to the SharePoint Master page without touching any code in the SharePoint Master page. "It's is a container type control which can holds child controls on it.

This is the simplest explanation for the SharePoint delegate controls but this also may confuse you. So let's further simplify it.

SharePoint Master Page design is a way of leaving place holders (Not a place holder really but you get the idea) to some controls (Delegate Controls) that has a machinist to inject.

Assume this is our SharePoint Master page.

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The Red Rectangle (SmallSearchInputBox) is a delegate control. It means the textbox and other functionalities in that search box not written in the master page. Master page just have a placeholder with id SmallSearchInputBox and which is going to be dynamically replaced by search box at run time.

Master Page code just looks like this.

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There are few delegate controls defined in the SharePoint Master page.

Why we need Delegate Controls

1. We can inject controls to master page without changing any code. For example, you need a custom control to put in the place of a small search box. So you can create a control and activate the control using a feature.Then the control will display in the place of the search box b the t good thing is you didn’t touch any master page code.

2. You can customize the master page delegate controls dynamically by user permissions,URLs, or any other custom rule.

3. Recently, we had a problem that we needed to include some custom user validation for each and every SharePoint page. So we finally decided to put that code in AdditionalPageHead so it will apply to all pages and we need to simply create a control to inject to the delegate control.

SharePoint 2010 and SharePoint 2013

AdditionalPageHead

  • This is top most delegate control in the master page. This delegate allows multiple controls. You can use this delegate to inject JavaScript to SharePoint master, inject custom logic and etc. Good thing about the AdditionalPageHead control is it lies between the HTML head tags. Therefore, it is not a control with interface. You can specify a control which only has code to do whatever you need in onLoad event.

GlobalNavigation

  • Global navigation is top most visible control collection. You can add your delegate controls to this location as well.
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GlobalSiteLink3
  • This delegate control handles social icons in the site. You can change these two icons by creating a delegate control.

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GlobalDelegate2

  • SharePoint dashboard control handles using this delegate.

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GlobalDelegate0

  • You can change this menu (maybe add more items to it) using this delegate control.

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PublishingConsole

  • This delegate control holds the server ribbon. Normally, we don'tt use it to customize the server ribbon. Of course, if you want you can.. 

TopNavigationDataSource

  • This delegate is used for default top navigation. You can override the data source by adding a custom data source.

SmallSearchInputBox

  • This control handles small search control in the master page.

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QuickLaunchDataSource

  • This delegate control provides a mechanism to override left side panel. So you can create your own data source and set it as a Quick launch data source with out changing the master page.

TreeViewAndDataSource

  • Treeview is the another navigation apart from quick launch and top link. You can change treeview’s default data source by providing custom data source to this delegate.

New Delegate controls in SharePoint 2013

SuiteLinksDelegate

  • This delegate handles these links in SharePoint 2013. So if you want to add a another link or some other component this is the delegate you need to use it.

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SuiteBarBrandingDelegate

  • This delegate cares about top left site logo and text. If you are interested in any other you can put it in here.

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PromotedActions

  • You can add controls in between Share and Follow. This holds empty controllers by default.

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