Microsoft SharePoint 2007 Technologies

546 17.3 Working with Document Libraries—Event Exercise

There are plenty of tools accessible via the Internet and downloadable

for free, that allow you to easily register and unregister event handlers

through a GUI type application. Alternatively, you can create your own cus-

tom application now that you know how to enumerate, register, and unregis-

ter event handlers.

17.3 Working with Document Libraries—Event

Exercise

The WSS 3.0 event architecture has improved greatly since its predecessor

and provides developers with a great platform for extending the base prod-

uct functionality. In this final section, we will walk through an exercise that

demonstrates the creation of an event handler that overrides the

SPItemEventReceiver class.

Those of you familiar with managing the permissions and roles for pub-

lic folders in Microsoft Exchange should be aware that you can assign per-

missions to determine which users are allowed the ability to create folders.

SharePoint Server 2007 and WSS 3.0 gives you the option to turn off the

create folder interface, which basically determines whether the “New Folder”

option appears on the New menu. This menu option is available on the Doc-

ument Library Advanced Settings page (Figure 17.29). It does not remove

the functionality itself, nor does it apply any permissions-based logic for

accessing the Create Folder page. If you know how to navigate to the Create

Folder page, by perhaps remembering the URL, then you can create a folder

as you would if the menu option existed. Furthermore, out of the box you

cannot define which users are allowed the ability to create or delete folders

based on their group membership or permissions; however, this functionality

can be provided through events.

In this exercise we will create an event handler that ensures only mem-

bers of the “Classified Users” SharePoint group have the ability to create or

delete folders in all the document libraries within a site. Users who are not

members of the “Classified” SharePoint group may only delete the docu-

ments that they created. In addition, when a document is added to a docu-

ment library, a link to that document is inserted into the “Classified Links”

list at the root of the site collection. Upon deletion of a document, we also

need to remove any links to that document that have been added to the

“Classified Links” list. Please note that the code used throughout this chapter

is for demonstration purposes only, as it has not been thoroughly tested and

does not contain the appropriate exception handling required of a produc-

tion application. Nevertheless, it illustrates the power of and some potential

uses for leveraging the event architecture when extending and customizing

your SharePoint implementation.

17.3 Working with Document Libraries—Event Exercise 547

Chapter 17

At a very high level, the steps involved include creating an event han-

dler that inherits the

SPItemEventReceiver class and overrides the

ItemDeleting, ItemAdding, and ItemAdded events. The ItemDeleting

method checks the content type, then checks for group membership to

determine whether the user is allowed to proceed. The

ItemAdding

method also checks the content type of the item being added, then checks

for group membership to determine whether the user is allowed to create a

folder in the document library. Finally, the

ItemAdded event checks the

content type of the item that was just added to the document library, and if

it is a document, a link to that document is added to the “Classified Links”

list. Once the event handler is created, we will deploy the event handler and

register it using a Feature. Note that we are using C# for this exercise.

Figure 17.29

Tur n folders on

and off.