windows 8 mobile c# code help - i need code for launch calendar,alaram,calculator - all installed apps with it's app name

It's the same thing (or you didn't describe the problem correctly and are in the wrong forum).

There is no programmatic way for a Windows Store app to explicitly launch another application, and there is no voice control system in-box for Windows Store apps.

As Sheng Jiang said, the security and privacy system prevents general purpose apps from enumerating the other apps on the system.

You could write a launcher as a desktop app, but that's a topic for another forum.

--Rob