I guess this is quite the easy one but the fact is that while I was searching the web for this answer it was very hard to find.
This is something I knew and forgot so it is good that I will have it here for future quick reference.
Just use:
Environment.TickCount
This will return the time in milliseconds that has passed since the last boot.
Quick Note:
I have read here that this might overflow on systems running for a few days, they also give a solution. as I am using this for a Windows Mobile device I don’t have that option. (CF.Net being deprecated and all…)
Hope you found this faster then I did.
Good luck,
Nadav