Sharepoint 2010 WSP file cannot activate and solution

Upload WSP file之後，Activate按鈕是disabled的、無法啟用。

Solution:
登入管理網頁Central Administration -> Manage services on server -> 啟用 Microsoft SharePoint Foundation Sandboxed Code Service

Reference: http://blogs.msdn.com/b/tmathis/archive/2010/02/28/activate-disabled-for-sharepoint-2010-sandbox-solution.aspx