from Google
An .axd file is a HTTP Handler file. There are two types of .axd files.
- ScriptResource.axd
- WebResource.axd
These are files which are generated at runtime whenever you use ScriptManager in your Web app. This is being generated only once when you deploy it on the server.
Simply put the ScriptResource.AXD contains all of the clientside javascript routines for Ajax. Just because you include a scriptmanager that loads a script file it will never appear as a ScriptResource.AXD - instead it will be merely passed as the .js file you send if you reference a external script file. If you embed it in code then it may merely appear as part of the html as a tag and code but depending if you code according to how the ToolKit handles it - may or may not appear as as a ScriptResource.axd. ScriptResource.axd is only introduced with AJAX and you will never see it elsewhere
And ofcourse it is necessary
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…