Silverlight started its life as an in-browser technology offering rich UX, media playing capabilities, and animation. Starting with Version 3, Silverlight gained the ability to run applications outside the browser, as sandboxed desktop applications. In Silverlight 4, the out-of-browser feature gained a serious boost with the introduction of "elevated trust". Not only can you now access local files and folders on the user's computer (pending his/her approval for your application to run in elevated trust mode) but you can also use COM automation to connect to other applications, for example Microsoft Office. Other important features of out-of-browser applications are toast notifications (a notification API), full screen mode support (for kiosk-based applications), and complete control over the application window. A great example for an out-of-browser Silverlight application is Seesmic Desktop 2, which you can see in the following screenshot:
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While we won't go into detail here on how to create and work with out-of-browser applications, as we have a chapter dedicated to this subject later on, we will address some of the differences between in and out-of-browser applications as follows:
In-browser applications have 1 MB of isolation storage quota, as opposed to 25 MB quota for out-of-browser applications. Both quotas can be extended upon a request from the user.
Out-of-browser applications cannot interact with JavaScript and the HTML DOM (they don't have any HTML DOM to interact with as they aren't running inside a browser).
Out-of-browser applications can interact with the Windows 7 taskbar using COM automation in elevated trust mode and they can be pinned to the taskbar in Windows 7 while in-browser applications cannot.
Out-of-browser applications have no initial parameters like in-browser applications.
In order to update an out-of-browser application, the developer is required to implement a check for a newer version in his code, whereas in browser applications, it is done automatically.
The installation process of an out-of-browser application is quick and painless; the user either right-clicks on the application surface or chooses install, as shown in the following screenshot:
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To make things easier for the user, we can create an installation button that will initiate the installation process. We will discuss this method in Chapter 6, Interacting with the Host Platform of the book.
There is a lot more in the subject of out-of-browser applications and while this chapter only provided a glimpse of the possibilities of the features,Chapter 6, Interacting with the Host Platform, will dive much deeper into it.