The versionString parameter contains four integer values that are separated by dots, following the format: major.minor.build.revision (for example, "1.0.50232.0"). The sequence of integers represent the following Silverlight version values:
This method primarily supports the JavaScript helper method IsInstalled, which is defined in Silverlight.js. The main reason you typically need to know the installed Silverlight version is to change the information that is displayed to the user before you instantiate a Silverlight plug-in instance with content on your HTML page, and to anticipate whether your users will see the Silverlight update or installation dialog box. When you have an instantiated Silverlight plug-in that is already displaying content, checking the installed version is of lesser importance.