Quick Notes: Retrieving Values in Event Receivers using BeforeProperties and AfterProperties

In SharePoint Portal development there are many scenarios where we need to develop event receivers.

So for accessing list item/ library item values, we need to use BeforeProperties and AfterProperties of SharePoint Event receivers. But some times they give empty or null values.

Below chart gives great understanding of which values are populated in BeforeProperties , AfterProperties and properties.ListItem objects.

For list:

List	BeforeProperties	properties.ListItem	AfterProperties
ItemAdding	Empty	Null	New Value
ItemAdded	Empty	New Value	New Value
ItemUpdating	Empty	Old Values	Updated Values
ItemUpdated	Empty	Updated Values	Updated Values
ItemDeleting	Empty	Original Values	Empty
ItemDeleted	Empty	Null	Empty

For library:

List	BeforeProperties	properties.ListItem	AfterProperties
ItemAdding	Empty	Null	Empty
ItemAdded	Empty	New Value	Empty
ItemUpdating	Old Values	Old Values	Updated Values
ItemUpdated	Old Values	Updated Values	Updated Values
ItemDeleting	Empty	Original Values	Empty
ItemDeleted	Empty	Null	Empty

The Synergy MOSS blog has explain this more clearly, please check here for more details.

http://www.synergyonline.com/Blog/Lists/Posts/Post.aspx?ID=122

Good Post on "SP 2010: How To – Event Receivers and Custom Error Pages" by Tobias Zimmergren . 
http://zimmergren.net/technical/sp-2010-how-to-event-receivers-and-custom-error-pages