Before,After Properties and ListItem in Sharepoint 2010 Event Recievers

As we all know, event receivers are a great way to hook into various SharePoint events.  These can apply to Feature events such as FeatureActivated, List events such as FieldAdded, and many others.When working with events, you’ll quickly find that before (synchronous) and after (asynchronous) events exist, and the method suffix such as “ing” (e.g. ItemAdding) and “ed” (e.g. ItemAdded) will tell you whether it gets invoked before or after the actual change is made. 

Event receivers are common in SharePoint development so its better to understand the data available in each events. Sometimes as a developer we jump into coding before thinking about contextual data availability.One more important thing to notice list event receiver  and document library event receiver are different interns of contextual data availability.Following Table will give you a clear picture about the contextual data in each events.

  SharePointList

Event	BeforeProperties	AfterProperties	ListItem
ItemAdding	Null	New  Value	Null
ItemAdded	Null	New Value	New Value
ItemUpdating	Null	Changed Value	Original Value
ItemUpdated	Null	Changed Value	Changed Value
ItemDeleting	Null	Null	Original Value
ItemDeleted	Null	Null	Null

  SharePointDocument Library

Event	BeforeProperties	AfterProperties	ListItem
ItemAdding	Null	Null	Null
ItemAdded	Null	Null	New Value
ItemUpdating	Original Value	Changed Value	Original Value
ItemUpdated	Original Value	Changed Value	Changed Value
ItemDeleting	Null	Null	Original Value
ItemDeleted	Null	Null	Null

I hope this post gives you a better idea of how before and after events work for both lists and libraries.