How do I change the installation path of a web setup project?

Using the 开发者_运维技巧default web setup project, the installation will be in inetpub/wwwroot. I have tried to use custom action, and inside onInstall method, i did this.

Context.Parameters["targetdir"] = @"C:\testing";
base.Install(stateSaver);

I have already added /targetdir="[TARGETDIR]\" to custom action data for install and commit, but the installation path stays at wwwroot.

I understand that you can create a virtual directory 1st, and deploy using a normal web project using the same virtual directory name. But I'm wishing that steps could be reduced. Anyway advised to this?