I have encountered three similar situations where ASP.NET fires the page_load event twice, or more.
- In one scenario (on a postback) your page load gets called once for the postback (IsPostback = true) and then gets called again, with IsPostback = false, which can cause a world of mistery until you realize what is happening!
This is normally caused when using a GridView with an asp:ButtonField using ButtonType=Image. This is bug in the .NET framework which can be solved by using an asp:TemplateField with an asp:ImageButton defined within it.
- Another scenario is you get two or more page loads everytime you load the page, whether it is a postback or not. This is usually caused by one of your HTML elements referencing "" (blank) or "#" as a source for its data (e.g. image src="", or background="#ff0000"). This is because this source string is interpreted by the browser as a relative url (which will be the current page) and therefore the browser makes a request for the page for each HTML element that 'references' it.
To workaround this issue, make sure your images etc. reference at least something, even if it is '%20'. Also use CSS for any colouring, not HTML attributes.
- Another example I have found more recently, is when using as asp:ImageButton within a template field of a databound control, where the imageUrl (src) does not exist on the server (404) will cause firstly two postbacks both with IsPostback=true, but will not raise the click event. This problem does not exist in IE, but does in Firefox and potentially other browsers. To fix this, make sure that the image source of an image button exists on the server.