What's New: Sandboxed Solutions
A sandboxed solution is a new concept in Microsoft SharePoint Foundation that enables site collection users to upload their own custom code solutions.
Applies to: SharePoint Foundation 2010
The Sandbox Solution framework provides a mechanism for executing user-provided code outside of the IIS worker process. The Sandbox Solution framework should not be used as a mechanism for enforcing security boundaries when executing user code. Sandbox Solutions are not supported as a security boundary with user code, especially code of unknown origin. We advise against executing Sandbox Solutions of unknown origins.
A sandboxed solution uses a subset of the Microsoft.SharePoint namespace. These objects are marked in the object model to show their availability in a sandboxed solution. All sandboxed solutions are stored in a solution gallery. In addition, facilities are provided to help server farm administrators monitor and validate solutions that have been uploaded to these galleries. Performance can be monitored by measuring CPU execution time, memory consumption, and database query time. You can also monitor other aspects of operation, including abnormal termination, critical exceptions, unhandled exceptions, and data marshaling size.
Microsoft.SharePoint.dll APIs That Are Available from Sandboxed Solutions
Installing, Uninstalling, and Upgrading Sandboxed Solutions in SharePoint 2010