Sandboxed Solutions

Developing for SharePoint Online means developing sandboxed solutions. SharePoint Online is based on SharePoint 2010, and as such, provides the sandboxed solution architecture. As I explained in Chapter 3, developers can safely build custom applications and deploy them to the shared environment of SharePoint Online.

Sandboxed solutions are limited in scope. The API is a subset of the Microsoft.SharePoint API. However, many powerful options remain, including:

• Site columns
• Content types
• List definitions
• List instances
• Web Parts
• Workflows
• Custom actions
• SharePoint Designer workflow activities
• Event receivers
• Modules/files

Sandboxed solutions run in partial trust. They are only given access to features at the site collection level. This means they can't access web application–scoped features or farm-scoped features. They also can't access the file system. This means you can't create solutions that deploy files up to the server. Sandboxed solutions are not allowed to make external web service calls. The SharePoint solution can't reach outside of the sandbox. However, only code running on the server is sandboxed. Silverlight and JavaScript applications can provide a workaround for some of these limitations.