I have a very odd situation in my SharePoint staging environment. We recently stood up a new SharePoint 2010 server (single WFE + a DB server), and attached a backed-up content database from our existing environment. We created a new web application, and pointed it at the attached content database. All of our site collections, sites, lists, etc. appeared, and things appeared good.
We had deployed some custom content types to our existing environment prior to moving the database, and we wanted to upgrade those content types. Specifically, we attach event receivers to the content types (using code, not XML) and we needed to update the assembly version that those event receivers point to. So we ran our usual code (part of a feature receiver) to remove the event receivers, but to our surprise, the receivers remained.
In an attempt to remedy the situation, we wrote a console application that iterates over all content types (SPWeb.ContentTypes) in the root site of each site collection and deletes them, and then calls SPContentType.Update(true) on each content type. There are no errors returned from the call to Update, but again to our even greater surprise, SharePoint still reports the event receivers are attached.
In a desparate last ditch effort, we even went into the content database (after taking a snapshot -- and remember, this is staging, not production!) and manually DELETED the offending receivers from the EventReceivers table. We figured that should have at least some kind of effect. Alas, SharePoint still reports the receivers as being present.
We perform these types of upgrades on content type event receivers all the time, but have never run into this issue on any other SharePoint farm. Does it sound like an environmental problem? Is it something that could have been caused by moving the content database? Any help would be appreciated, because we are completely stumped at this point.
1st of all, I will never recommend changing anything in DB. It will surely give you trouble in long run.
You did mention that you tried to remove the event reciever from Web level but not sure if you have tried removing it from List/Library level
Use ContentTypeUsage class and try deleting from List/Library level
http://msdn.microsoft.com/en-us/library/microsoft.sharepoint.spcontenttypeusage.aspx