does this happen to u sometimes:

After u change the ID of a server control in the aspx view from let's say: "ControlId" to "NewControlId", then and u change the ID in all the code behind to take into consideration the new ID value, when we builde, those changes sometimes don t reflect during the build, and we get the error for example:

Name 'NewControlId' is not declared.

or something like that

any idea pls?

It happens a lot for example with AjaxToolKitControls may be with regular controls as well