I keep running into people having this problem, so I’m going to put this out there in the hopes that someone will find this BEFORE they pull out their hair…
If you have an event handler that is not firing in your ASP.NET page and the control that is supposed to be firing it is a textbox, drop down list, checkbox, etc. (events like OnChanged would be what you would most likely have this problem with) then you MUST set the “AutoPostBack” property of the form control(s) to true… If you don’t do this, it will never fire your events because it will not come back to the server for anything until you click a button or something else that causes a postback happens.
Keep in mind that causing a postback on events like these could cause a good bit more traffic than you think and it will also cause the page to jump back to the top if you don’t use the tip from my next blog entry…