This question has been asked from my friend that The Name 'Spsecurity' does not exist in the current context. Therefore, I want to share this knowledge with you. SpSecurity Class is not avaible in sandboxed solutions. SpSecurity is static class to provide security management properties and methods.
When you deploy as a sandboxed solution in SharePoint solution you will get the SpSecurity error as shown below.

When you deploy as a farm solution in SharePoint solution you will see that SpSecurity class is available in the current context as shown below.
