How to update and insert multiple rows at once?

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SQL-Server-2005

C#3.0

C#

ASP.NET

, +

Hi,
My requirement is as follows:
In a single web page I have a image slider[JQuery] type control.When I am clicking on any particular image,all the related information are coming in the fields[text boxes]below.
there are two scenarios:
1.I can change the values in the text boxes.Again select another image,change the related infos the text boxes.this way.But I want to update all the information by clicking one button,not every time.[Bulk Update]
2.There may be blank image,for which I have to give new information.[bulk Insert in case the info is not existing].

Both the things I will do on a single button click.
Now my question is:
I want to write a sp which will bulk insert if the row was not present or it will update the row if present.
How to write such SP for <b>bulk Insert/Update</b>?For single row,I can do.
[Assuming table structure:(Mov_id pk,Mov_name,Cost)it should be some thing like this:
if Mov_id not in table_Movie
insert into ....
else update table_Movie set .... where... ]This is for single row.I want to do in bulk.
Please help ASAP as I am in urgent need..