When is image within the updateprogress control sent to client in asp.net ???

Question

When is image withing update-progress control sent to client ??? Say a asp.net page has AJAX implemented. We use update panel and update progress. Further we set a .gif image in the update progress control. Now when will the image be sent to the client ? At the first time when the page was requested or when the update panel was updated ? I read about the topic at http://jai-on-asp.blogspot.com/2010/01/ajax-for-aspnet.html

Answer 1

The browser will request the image from the server as soon as one of the HTML elements specifies the url for the image.

With most update progress controls this will not happen until the javascript running on the client fires off and makes the control visible.