For a while ago I needed to provide an alternative solution when Silverlight isn’t installed. I searched  for javascript code for this and found this:

• A blog post about that: Piotr Puszkiewicz’s Silverlight Blog. Determining if Silverlight is installed using Javascript.
• A more advanced javascript function which can even determine the version of the Silerlight can be pulled from Silverlight.js library.

I didn’t need to determine the version of Silverlight, so I wrote a simplified js function (but it works in all browsers): [sourcecode language=“javascript”] var isSilverlightInstalled = function() { var installed = false; try { installed = !!navigator.plugins[“Silverlight Plug-In”] || !!(window.ActiveXObject && new ActiveXObject(‘AgControl.AgControl’)); } catch (e) {} return installed; };[/sourcecode] This function first checks if a Silverlight plugin is installed in almost all web browsers except IE, then if it is not it tries to create an ActiveXObject (IE) for Silverlight. If an error occurs, the function returns false and indicates that Silverlight is not available.