I just lost 5 hours looking for a answer which i haven't been able to find :p
First, I'd like to force a trusted application (i need to access the file system) to display into the browser. Based on what i found on google a trusted application must be installed and launched as a desktop application (also called out-of-browser application).
So, i want to have an installed application on the client side but meanwhile, the user must also be able to start this same application into a browser window when he goes on my web site. Is this possible ?
Second, I'd like to give to the user the possibility to start the application from the browser. To be clear, the application is installed on the client computer but i want a button on my web site which starts the desktop application. How can i do that ?
Thanks
The answers are sort of and no.
Yes you can run an application that has been installed on the client also in the browser. However, not all of the installed application features will be available. Anything that requires elevated trust will not work inside the browser.
No you can't launch the installed application programmatically from within code running in the browser. The best you can do is display a polite message to the user to the effect that they have this app already installed and in order to access all of its feature they will need to launch it.
Yes, it is possbile since Silverlight 5, see my answer on silverlight-4-elevated-permission-inside-the-browser
来源：https://stackoverflow.com/questions/2530261/silverlight-4-launch-a-trusted-application-into-the-browser