Hi There,
These two are the triggers to the postBack the Page to the server when using update Panel.
1. AsyncPostBackTrigger
it is the one which enforces Asynchonous post back of the Page.., i.e. the AJAX way. The data will be transacted without full post back. When you are using functionalities like login, you may use this.
Ex. You are having two dropDowns Viz., Countries and States. the states should be loaded when a country is selected and it should be changed on Countries change.
You may use AsyncPostBackTrigger in this scinario., which will populate the states ddl without full post back.
2. PostBackTrigger
It is the one which does not follow the AJAX functioalities., but the full post back as usually(as Without using UpdatePanel). Situtions are there where you would not like to enforce Partial Post back (as explained in Point 1. above). Like you are having FileUpload Control withing the UpdatePanel and when you do it by AsyncPostBack, you will not get any values to the server. It requires Full PostBack. in such a case you should use this trigger.
Thanks and Regards,
Rk_Hirpara.
