ASP.NET创建的线程的用户由<identity impersonate="true"/> 改为NT AUTHORITY\NETWORK SERVICE， 引起"System.UnauthorizedAccessException"，"拒绝访问"

Dim thr As Threading.Thread
Dim l As System.Security.Principal.WindowsIdentity

Function print()
thr = New Threading.Thread(AddressOf printAutoCAD)
thr.Start()
l = System.Security.Principal.WindowsIdentity.GetCurrent
End Function

Private Sub printAutoCAD()
System.Security.Principal.WindowsIdentity.Impersonate(l.Token)
...
End Function