One of the cool new feature in SharePoint 2010 is Document Sets. They can easily replace Folders in SharePoint 2010. Document Sets help you organize related documents into a ‘set’ and also provide a user interface (home page) to manage them. You can also use metadata against the document set which makes it even more useful!
But one of the most asked feature is missing from the SharePoint UI – Downloading the whole document set, along with its files as a zip file!
But if you look into the SharePoint 2010 SDK, there is code that extends the Document Set Ribbon tab to download the document set!
It turns out downloading the document set can be done using only Server Object Model (SharePoint API) . Microsoft uses the same for some of the document set functions like sending the document set to content organizers.
Unfortunately, this option is not available in the Client Object Model and in Sandboxed environment. The reasons are quite obvious:
1) Client Object model includes only SharePoint Foundation 2010 features. Document Set is a SharePoint Server 2010 feature.
2) Microsoft.Office.DocumentManagement.dll should be referenced to work with Document Sets which is not sandboxed.
You can download the full solution along with the source code from here: http://bit.ly/docsetdownload (The SDK does not have the full working project/solution)
Once deployed, you will get Download Copy option inside your document set: