Within the SharePoint UI, there are a number of drop-down menu’s that can be customised. These are known as CustomActions – and it’s as easy as editing some XML file to include new options – and then develop the specific functionality that the menu option will initiate.
SharePoint gives a lot of opportunities to customize the user interface and add your own customizations.
There are a lot of examples of modifying the ‘EditControlBlock’, the drop down actions list shown on list items in a list view, and adding custom functionality to the ‘Actions’ menu of the list view.
The sample project adds two items to a list view
…one to the ‘EditControlBlock’, which allows you to make a copy of the selected list item
…another which adds an items to the Actions menu, which allows you to delete all the items in the current list.
Click here to read the full article : Sample CustomActions for SharePoint