CS0102 Definition for Rowchange eventhandler

I have built a web application that is deployed and in use. Updated a dataset in it with new Table Adapters in Development environment to meet some new needs of users. Tested it and ready to deploy. Instead of overwriting the old Dataset in Production I pasted it to keep as backup and then when I copied the one from Development environment to overwrite the one in production. as soon as I RUN THE APPLICATION it says CS0102 Definition of TableAdapterRowchangeEvent Handler already exists. When I look at it in development environment it is not duplicated then why the error. After some thinking and loking at details of error, realised it was coming because of the old Dataset which I had kept as a backup. since both the datasets had the same table adapter. Once i moved it out No Issues. Soo as i always say, Issues are usually simple, but we always think of complex things...