I want to add a custom button in master page just on right side of a page.My question is what is the approach to do this.I will deploy it as a part of feature so admin can deactivate the same to hide the button.
do I need to use delegate control for this purpose.Can anyone please give some insight on this. Thanks.
Yes, you should create a delegate control to accomplish this. (Assuming you are on-premises, not SPO.)
The out of the box search control (the existing box and button) are deployed via a delegate control, and that is the recommended approach to change it.
Be aware of the scope of the feature that you create. You can override the OOB behavior at any scope, which may or may not be what you want.
