Slow performance on asp.net website, where to start looking for the problem?

Question

I have developed a site using Asp.net C# 3.5 and now I feel that some of the pages are loading reeeaaally slooooow. I now need to start going through the website and try to find out whats making it so slow. But I don't know where to start, whats most likely causing the problem? Where do you usually start when trying to find out what is wrong?

One page that is very slow uses the following:

• Asp.net C# 3.5
• AjaxControlToolkit (http://www.asp.net/ajax/AjaxControlToolkit/Samples/)
  • RoundedCornersExtender
  • CollapsiblePanelExtender
• Two different UpdatePanels
• 11 connections to a MySql database (one quite heavy, using some unions and inner joins)
• Most of the connections to the database results in populating FormViews or GridViews, so totally I have 2 formviews and 6 gridviews on the page (every gridview show max 10 items)
• Can a CSS-file slow down the site? The CSS file I use is about 60kb.

Can using the AjaxControlToolkit make the site slow? Is there a better way to use javascripts on the site?

I understand that it's impossible for you to help me locate the problem with slow load but where you would start to look for the problem? The DataControllers? The AjaxControlToolkit? The sql? Is it an easy way to find out if a query in mysql is slow? And what is slow? Is 0.3s slow for a large query?

As you see I have many questions, maybe you could just help me start working in the right direction, thanks really much for your help!

Answer 1

You could start adding Trace="True" into your <%@ Page %> directive and see where your pages spent most time; also check your web.config and config debug is disabled.

You can also use Performance Monitor to help you to identify your application main bottlenecks