It's normal that all code that you execute in your code behind, won't do the
job, because it executes on the server and you only get server's printers. But I
am very sceptic about getting printer names with JavaScript... Maybe I'm wrong.

I need the printer list  from the server.

So,how can I get the list  of all printers from the server?
I use System.Drawing.Printing.PrinterSettings.InstalledPrinters
but this property  only return  the local  printers and I want as well the
network printers added  on the server computer.

If I call this property
from a windows applications it returns the entire printer list (network
printers as well).
So, how can I get the list of all the printers?

I think InstalledPrinters property  should also return  all network printers, but
you must enshure there are any for your Web app user (default ASPNET user).
Probably this is the problem.

You're going to need to switch ASP.Net over to a domain account which
has printer access in order to do this, as the ASPNet user will not have
any rights on a machine other than the webserver.

You can change the worker process' account in the processModel section
of the machine.config file.