Cannot detect Sony Xperia in Eclipse

Question

I am totally new at testing apps on devices, especially the Sony Xperia. I am testing apps using the Android emulator, but I have now a Sony Xperia. First I have connected

Answer 1

Even though this question was posted long time ago, I didn't find 100% correct answer from previous replies. Most of replies are useful, but here is one final step for debugging apps on Sony Xperia devices.
My Sony Xperia T has not been visible in Eclipse even though I installed PC Companion and in mobile phone, I set developers options debugging mode!

Xperia has very strange option:
Settings > Xperia > USB Connectivity > USB connection mode
and select Mass storage mode (MSC).
Note that the USB cable must be unplugged to change this option. By default, Media transfer mode (MTP) was selected. If MTP is selected even little bug is shown in notification bar debugging is not possible!