VS 2010 Impersonate current windows identity vs logonuser

I have a wcf service with a method that copies files from a network share to a temp folder on the web server. It works perfectly if I use the logonuser function but not if I use the currentwindowsidentity.

I need to be able it impersonate the currently logged in user, not have to specify any credentials. I have found other users report the same problem as well and I have not been able to find a solution.

Any help would be greatly appreciated.

Thanks

Code that does do impersonation but cannot see the files on the share. I can check

Public Function CopyFiletoSite(filename As String, id As Integer) As String

Try

Dim impersonationContext As System.Security.Principal.WindowsImpersonationContext
Dim currentWindowsIdentity As System.Security.Principal.WindowsIdentity

currentWindowsIdentity = CType(WindowsIdentity.GetCurrent, System.Security.Principal.WindowsIdentity)
impersonationContext = currentWindowsIdentity.Impersonate()

For Each File In Directory.GetFiles(HostingEnvironment.ApplicationPhysicalPath & "Clientbin\Images\")

IO.File.Delete(File.ToString)

Next

If IO.File.Exists(filename) Then

Dim tmpfilename As String = id & ".tif"

IO.File.Copy(filename, (HostingEnvironment.ApplicationPhysicalPath & "Clientbin\Images\" & tmpfilename), True)

Return tmpfilename

Else

Return "Cannot find this file:" & filename & " Current user is" & ServiceSecurityContext.Current.WindowsIdentity.Name.ToString

End If

impersonationContext.Undo()

Return "Impersonate"


Catch ex As Exception

Return ex.Message


End Try
End Function

'Code that works but i have to specify domain, user, and password which I cannot do in live environment. I need to be able to detect and use the current users context.

Dim LOGON32_LOGON_INTERACTIVE As Integer = 2
Dim LOGON32_PROVIDER_DEFAULT As Integer = 0


Dim impersonationContext As WindowsImpersonationContext


Declare Function LogonUserA Lib "advapi32.dll" (ByVal lpszUsername As String, _
ByVal lpszDomain As String, _
ByVal lpszPassword As String, _
ByVal dwLogonType As Integer, _
ByVal dwLogonProvider As Integer, _
ByRef phToken As IntPtr) As Integer

Declare Auto Function DuplicateToken Lib "advapi32.dll" ( _
ByVal ExistingTokenHandle As IntPtr, _
ByVal ImpersonationLevel As Integer, _
ByRef DuplicateTokenHandle As IntPtr) As Integer
Declare Auto Function RevertToSelf Lib "advapi32.dll" () As Long
Declare Auto Function CloseHandle Lib "kernel32.dll" (ByVal handle As IntPtr) As Long
Private Function impersonateValidUser(ByVal userName As String, _
ByVal domain As String, ByVal password As String) As Boolean

Dim tempWindowsIdentity As WindowsIdentity
Dim token As IntPtr = IntPtr.Zero
Dim tokenDuplicate As IntPtr = IntPtr.Zero
impersonateValidUser = False

If RevertToSelf() Then
If LogonUserA(userName, domain, password, LOGON32_LOGON_INTERACTIVE,
LOGON32_PROVIDER_DEFAULT, token) <> 0 Then
If DuplicateToken(token, 2, tokenDuplicate) <> 0 Then
tempWindowsIdentity = New WindowsIdentity(tokenDuplicate)
impersonationContext = tempWindowsIdentity.Impersonate()
If Not impersonationContext Is Nothing Then
impersonateValidUser = True
End If
End If
End If
End If
If Not tokenDuplicate.Equals(IntPtr.Zero) Then
CloseHandle(tokenDuplicate)
End If
If Not token.Equals(IntPtr.Zero) Then
CloseHandle(token)
End If
End Function

Private Sub undoImpersonation()
impersonationContext.Undo()
End Sub



Public Function CopyFiletoSite(filename As String, id As Integer) As String
Try


If impersonateValidUser(DeNull(ConfigurationManager.AppSettings("DomainUserName").ToString), DeNull(ConfigurationManager.AppSettings("DomainName").ToString), DeNull(ConfigurationManager.AppSettings("DomainPassword").ToString)) Then

'Insert your code that runs under the security context of a specific user here.
For Each File In Directory.GetFiles(HostingEnvironment.ApplicationPhysicalPath & "Clientbin\Images\")

IO.File.Delete(File.ToString)

Next

If IO.File.Exists(filename) Then

Dim tmpfilename As String = id & ".tif"

IO.File.Copy(filename, (HostingEnvironment.ApplicationPhysicalPath & "Clientbin\Images\" & tmpfilename), True)

Return tmpfilename

Else

Return "Cannot find this file:" & filename & " Current user is" & ServiceSecurityContext.Current.WindowsIdentity.Name.ToString

End If

undoImpersonation()
Else
''impersonation failed"
End If


Return "Impersonate"


Catch ex As Exception

Return ex.Message


End Try
End Function