How Value Return in Before Properties, After Properties and ListItem using EventReceiver in SharePoint2010

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 items of contextual data availability.Following Table will give you a clear picture about the contextual data in each events.

• SharePoint List

Event	Before Properties Returns	After Properties Returns	ListItem Returns	Event Type
Item Adding	Null Value	New Value	Null Value	Synchronous
Item Updated	Null Value	New Value	New Value	Asynchronous
Item Updating	Null Value	Changed Value	Current Value	Synchronous
Item Updated	Null Value	Changed Value	New Value	Asynchronous
Item Deleting	Null Value	Null Value	Current Value	Synchronous
Item Deleted	Null Value	Null Value	Null Value	Asynchronous

• SharePoint Document Library

Event	Before Properties Returns	After Properties Returns	ListItem Returns	Event Type
Item Adding	Null Value	Null Value	Null Value	Synchronous
Item Updated	Null Value	Null Value	New Value	Asynchronous
Item Updating	Current Value	Changed Value	Current Value	Synchronous
Item Updated	Current Value	Changed Value	New Value	Asynchronous
Item Deleting	Null Value	Null Value	Current Value	Synchronous
Item Deleted	Null Value	Null Value	Null Value	Asynchronous