what is trigger?

hi Ram,

Are talking About "Trigger in SQL Server" Or Trigger in Ajax?

A trigger is a special kind of a store procedure that executes in response to certain action on the table like insertion, deletion or updation of data. It is a database object which is bound to a table and is executed automatically. You can't explicitly invoke triggers. The only way to do this is by performing the required action no the table that they are assigned to.

Please refer

SQL Server:

http://technet.microsoft.com/en-us/library/ms189799.aspx
http://www.databasejournal.com/features/mssql/article.php/3837541/DML-Triggers-in-SQL-Server-2008.htm

Ajax:

In AJAX, we can specify areas of a page to be refreshed without refreshing the whole page. For this, we use UpdatePanels, which also have the ability to make use of triggers. These triggers allow us to specify which control initiates a certain postback. We can choose to initiate a partial postback, or a full one.

http://www.ajaxtutorials.com/ajax-tutorials/using-updatepanel-triggers-in-asp-net-3-5/
http://www.asp.net/web-forms/tutorials/aspnet-ajax/understanding-asp-net-ajax-updatepanel-triggers

hope this will hekp you.