SharePoint Event Handlers – Asynchronous Vs Synchronous

There is a little puzzlement among Asynchronousand Synchronous events, however I believe after reading this article, there will be no place for confusion in your brain, the reason for that I go behind a childlike practice to memorize what is Asynchronous ? and what is Synchronous ?

The same babyish method, I want to share with you.

A for Apple, A for Asynchronous and A for After events, so all Asynchronous events occur after the event, which does not stop the code to execute. All Asynchronous events end with ‘ed’ letters like SiteDeleted, FieldAdded, ItemAdded etc.

Now, let’s talk on the subject of Synchronous events, all Synchronous events  occur before the event, which stop the code to execute. All Synchronous events end with ‘ing’ letters like SiteDeleting, FieldAdding, ItemAdding etc.

SPWebEventReceiver Asynchronous Events

SiteDeleted	Occurs after an existing site collection deleted.
WebDeleted	Occurs after an existing web site is completely deleted.
WebMoved	Occurs after an existing web site has been moved.

SPWebEventReceiver Synchronous Events

SiteDeleting	Occurs before an existing site collection is being deleted.
WebDeleting	Occurs before an existing web site is deleted.
WebMoving	Occurs before an existing web site has been renamed or moved

SPListEventReceiver Asynchronous Methods

FieldAdded	Occurs after a field link is added.
FieldDeleted	Occurs after a field has been removed from the list.
FieldUpdated	Occurs after a field link has been updated

SPListEventReceiver Synchronous Methods

FieldAdding	Occurs before a field link is added to a content type.
FieldDeleting	Occurs before a field is removed from the list.
FieldUpdating	Occurs before a field link is updated

SPItemEventReceiver Asynchronous Methods

ItemAdded	Occurs after a new item has been added
ItemAttachmentAdded	Occurs after an attachment added to an item.
ItemAttachmentDeleted	Occurs after an attachment removed from an item.
ItemCheckedOut	Occurs after an item is checked out.
ItemDeleted	Occurs after an item is completely deleted.
ItemFileMoved	Occurs after a file is moved.
ItemUpdated	Occurs after an item is modified/edited.

SPListItemEventReceiver Synchronous Methods

ItemAdding	Occurs before a new item is added.
ItemAttachmentAdding	Occurs before an attachment is added to an item.
ItemAttachmentDeleting	Occurs before an attachment when a user removed from an item.
ItemCheckingIn	Occurs before a file is checking-in.
ItemCheckingOut	Occurs before an item is checking-out.
ItemDeleting	Occurs before an item is completely deleted.
ItemFileMoving	Occurs before a file is moved.
ItemUncheckedOut	Occurs before an item is unchecked out.
ItemUncheckingOut	Before event that occurs when an item is being unchecked out.
ItemUpdating	Occurs before an existing item is modified/edited.

SharePoint Foundation 2010 New Events

Microsoft added several new events to SharePoint Foundation 2010 on Site, List and Item level. These fresh events are intended to meet up the requirements and for better elasticity.

SPWebEventReceiver

WebAdding	Occurs before a new web site is created.
WebProvisioned	Occurs after the web is provisioned.

WebAdding: event arises prior to a fresh web site is created, we can control the website to create or not to create by WebAdding event, then no SharePoint site is created and the provisioning process is not started.

WebProvisioned: event arise after the web is totally provisioned and process has stopped up. WebProvisioned can be configured to control in any synchronous or asynchronous methods.

If user wants to add few webparts to the newly provisioned web we can use this event to meet up the necessity

SPListEventReceiver

ListAdding	Occurs before a list is created.
ListAdded	Occurs after a list is created.
ListDeleting	Occurs before a list is deleted.
ListDeleted	Occurs after a list is deleted.

Reference:
http://msdn.microsoft.com/en-us/library/gg749858(v=office.14).aspx