Hi,

messed around with the IPrincipal and IIdentity a little bit. Threads on this indicate that this is a general issue. Here my contribution:

web.config contains this:
<authentication mode="Windows" />
<identity impersonate="true"
    userName="HansWurschd"
    password="HansWurschd" />
!!!! be sure to use asp_setreg in real life !!!!
<authorization>
  <deny users="?" />
  <allow users="*" />
</authorization>

In Global.asax put the following code:

protected void WindowsAuthentication_OnAuthenticate(object source , WindowsAuthenticationEventArgs e){
// fires on each Request and puts custom user in Context
e.User = new KLBPrincipal(e.Identity, "egon bahr");
}

Then you can Access the user as follows.

private void Button1_Click(object sender, System.EventArgs e) {
 if(Context.User.Identity.IsAuthenticated){
   // impersonated user
   Response.Write(WindowsIdentity.GetCurrent().Name + "<br>");
   // user, sitting in front of the box
   Response.Write("Context.User.Identity.Name " + Context.User.Identity.Name + "<br><br>");
  }
}

If it takes considerable time to rebuild your user, consider whether to put it into session state, get it lazy loading or to use some other "persistence" mechanism. Have a look on the UIP from Microsoft. Cool stuff!!!

HTH,
David