windows service set up issue

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i have a setup project setup1 which deploys two windows services windows
service1,windows service2.i also added some custom installation actions into
it using projectinstaller.cs.In windowsservice1 oninstall event,i attached a
database ;(create database for attach command) .
in windowsservice2 onuninstall event,i deletes the databse using "drop
database";
the setup exe installs the windows services successfully.but when i
uninstall them, the drop database does not work as sql server places a lock
on mdf files.(cant drop database as mdf file is in use).how can i solve this
problem. Also since uninstall operation is not transactional, only the
windowsservice1 gets uninstalled. when i again try to uninstall ,it shows
"the specified service does not exist as an i nstalled service"(probably the
setup again tries to unstall the already uninstalled windowsservice1).

How can i solve these problems?
i need a way to unlock the mdf files before executing drop database
command
And in unstall event of windows service 1, i need a way to check if it is
already uninstalled
public override void UnInstall()
{
how to check whether the service already uninstalled()?;
base.Uninstall();

}