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Windows Impersonation using C#

, 29 Apr 2003 CPOL 512.8K 12.2K 141
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An article demonstrating how to use Windows impersonation in your C# code



I've been a member of the CodeProject for over 3 years now, and still haven't contributed any articles - until now.

While designing a Windows Forms-based application, to administrate containers in our Active Directory, I needed a way to allow binding to the AD using alternate credentials. Windows impersonation was the answer. This sample app demonstrates how to use unmanaged code by calling LogonUser() contained within the advapi32.dll, and pass a token handle back to your .NET application using WindowsImpersonationContext.

One of the downfalls to the LogonUser()function is that the password get passed in clear-text.

Partial Source Code

using System.Runtime.InteropServices; // DllImport
using System.Security.Principal; // WindowsImpersonationContext
using System.Security.Permissions; // PermissionSetAttribute

public WindowsImpersonationContext 
    ImpersonateUser(string sUsername, string sDomain, string sPassword)
    // initialize tokens
    IntPtr pExistingTokenHandle = new IntPtr(0);
    IntPtr pDuplicateTokenHandle = new IntPtr(0);
    pExistingTokenHandle = IntPtr.Zero;
    pDuplicateTokenHandle = IntPtr.Zero;
    // if domain name was blank, assume local machine
    if (sDomain == "")
        sDomain = System.Environment.MachineName;

        string sResult = null;

        const int LOGON32_PROVIDER_DEFAULT = 0;

        // create token
        const int LOGON32_LOGON_INTERACTIVE = 2;
        //const int SecurityImpersonation = 2;

        // get handle to token
        bool bImpersonated = LogonUser(sUsername, sDomain, sPassword, 
                ref pExistingTokenHandle);

        // did impersonation fail?
        if (false == bImpersonated)
            int nErrorCode = Marshal.GetLastWin32Error();
            sResult = "LogonUser() failed with error code: " + 
                nErrorCode + "\r\n";

            // show the reason why LogonUser failed
            MessageBox.Show(this, sResult, "Error", 
                MessageBoxButtons.OK, MessageBoxIcon.Error);

        // Get identity before impersonation
        sResult += "Before impersonation: " + 
            WindowsIdentity.GetCurrent().Name + "\r\n";

        bool bRetVal = DuplicateToken(pExistingTokenHandle, 
                ref pDuplicateTokenHandle);

        // did DuplicateToken fail?
        if (false == bRetVal)
            int nErrorCode = Marshal.GetLastWin32Error();
            // close existing handle
            sResult += "DuplicateToken() failed with error code: " 
                + nErrorCode + "\r\n";

            // show the reason why DuplicateToken failed
            MessageBox.Show(this, sResult, "Error", 
                MessageBoxButtons.OK, MessageBoxIcon.Error);
            return null;
            // create new identity using new primary token
            WindowsIdentity newId = new WindowsIdentity
            WindowsImpersonationContext impersonatedUser = 

            // check the identity after impersonation
            sResult += "After impersonation: " + 
                WindowsIdentity.GetCurrent().Name + "\r\n";
            MessageBox.Show(this, sResult, "Success", 
                MessageBoxButtons.OK, MessageBoxIcon.Information);
            return impersonatedUser;
    catch (Exception ex)
        throw ex;
        // close handle(s)
        if (pExistingTokenHandle != IntPtr.Zero)
        if (pDuplicateTokenHandle != IntPtr.Zero) 

Points of Interest

This code won't work on Windows 98 or ME because they do not utilize user tokens. Code was built and run using Visual Studio.NET 2002 on Windows XP Service Pack 1.

One of the other uses for this code I've found is, for instantiating COM components that must run in an alternate security context to that of the logged-on user.

If anyone has a more secure method of achieving the same thing, please let me know.


  • Version 1.0 - 04.25.03 - First release version


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Marc Merritt
United States United States
I live in southeastern Pennsylvania, USA with my lovely wife and two beautiful daughters. Life is good. My hobbies are motorcycles, motorcycles, and motorcycles.

I run a riders group called Twisties Motorcycle Club. If you're are a rider in the tri-state area, look us up!

You may also be interested in...

Comments and Discussions

QuestionSame user name before and after impersonation Pin
phoenicyan10hrs 20mins ago
memberphoenicyan10hrs 20mins ago 
GeneralMy vote of 5 Pin
srilekhamenon1-Sep-14 2:25
membersrilekhamenon1-Sep-14 2:25 
QuestionThanks a lot, you saved 2 hrs. Pin
Member 103845676-Nov-13 8:23
memberMember 103845676-Nov-13 8:23 
AnswerRe: Thanks a lot, you saved 2 hrs. Pin
Marc Merritt12-Nov-13 8:34
memberMarc Merritt12-Nov-13 8:34 
GeneralRe: Thanks a lot, you saved 2 hrs. Pin
Oded Arbel20-Mar-14 3:04
memberOded Arbel20-Mar-14 3:04 
GeneralRe: Thanks a lot, you saved 2 hrs. Pin
Marc Merritt20-Mar-14 3:10
memberMarc Merritt20-Mar-14 3:10 
GeneralRe: Thanks a lot, you saved 2 hrs. Pin
Guss7720-Mar-14 9:47
memberGuss7720-Mar-14 9:47 
Questionsource code help Pin
Pyakaa17-Dec-12 1:43
memberPyakaa17-Dec-12 1:43 
GeneralMy vote of 5 Pin
kerkenez20004-Apr-12 23:35
memberkerkenez20004-Apr-12 23:35 
QuestionCall LogonUser Pin
Member 822764117-Sep-11 13:40
memberMember 822764117-Sep-11 13:40 
QuestionPlease I need a Help Pin
kaiserssosse11-Aug-11 1:41
memberkaiserssosse11-Aug-11 1:41 
AnswerRe: Please I need a Help Pin
diialer21-Aug-11 7:36
memberdiialer21-Aug-11 7:36 
GeneralRe: Please I need a Help Pin
kaiserssosse21-Aug-11 21:03
memberkaiserssosse21-Aug-11 21:03 
GeneralIs Windows Impersionation Thread or Process Level ? Pin
Thomas Haller27-May-11 2:42
memberThomas Haller27-May-11 2:42 
GeneralThanks Pin
olivier gg14-Feb-11 8:43
memberolivier gg14-Feb-11 8:43 
GeneralWIndows 7 Pin
moralam13-Jul-10 7:58
membermoralam13-Jul-10 7:58 
Hello, I Try this method in windows 7 and not work, somebody have an update for run this one on Windows 7?
GeneralRe: WIndows 7 Pin
Marc Merritt28-Jan-13 5:25
memberMarc Merritt28-Jan-13 5:25 
QuestionCross domain impersonation Pin
atulsureka18-Apr-10 2:25
memberatulsureka18-Apr-10 2:25 
AnswerRe: Cross domain impersonation Pin
deadwood8827-Sep-10 2:00
memberdeadwood8827-Sep-10 2:00 
GeneralRe: Cross domain impersonation Pin
Cstruter26-Oct-10 21:38
memberCstruter26-Oct-10 21:38 
GeneralRe: Cross domain impersonation Pin
sabh2125-Jan-13 1:32
membersabh2125-Jan-13 1:32 
GeneralCreate a folder on a remote computer Pin
Shlomo6-Jan-10 1:52
memberShlomo6-Jan-10 1:52 
GeneralWindows 2008 server Pin
smithafebinkal3-Dec-08 18:45
membersmithafebinkal3-Dec-08 18:45 
GeneralThis process not working with a WPF application!!! Pin
Arshad Kunnath31-Jul-08 1:36
memberArshad Kunnath31-Jul-08 1:36 
GeneralRe: This process not working with a WPF application!!! Pin
Marc Merritt31-Jul-08 2:59
memberMarc Merritt31-Jul-08 2:59 
GeneralRe: This process not working with a WPF application!!! Pin
Matei Focseneanu12-May-10 5:15
memberMatei Focseneanu12-May-10 5:15 
GeneralRe: This process not working with a WPF application!!! Pin
Jason Jakob20-Jun-13 5:09
memberJason Jakob20-Jun-13 5:09 
QuestionIt may be.... Pin
Willian.BR15-May-08 8:55
memberWillian.BR15-May-08 8:55 
GeneralWindows CE .net Pin
questions_c1-Oct-07 2:28
memberquestions_c1-Oct-07 2:28 
GeneralRe: Windows CE .net Pin
Marc Merritt1-Oct-07 15:18
memberMarc Merritt1-Oct-07 15:18 
GeneralRe: Windows CE .net Pin
Pram_Singh4120-Jul-09 4:22
memberPram_Singh4120-Jul-09 4:22 
GeneralError Code 1326 [modified] Pin
collapo21-Aug-07 0:56
membercollapo21-Aug-07 0:56 
GeneralRe: Error Code 1326 Pin
mirh10-Oct-07 1:59
membermirh10-Oct-07 1:59 
GeneralRe: Error Code 1326 Pin
mustiy9-Feb-10 23:17
membermustiy9-Feb-10 23:17 
GeneralError 1314 Pin
m.aldegheri3-Aug-06 6:28
memberm.aldegheri3-Aug-06 6:28 
GeneralRe: Error 1314 Pin
m.aldegheri3-Aug-06 22:23
memberm.aldegheri3-Aug-06 22:23 
GeneralRe: Error 1314 Pin
MunkieFish11-Apr-07 7:49
memberMunkieFish11-Apr-07 7:49 
AnswerRe: Error 1314 Pin
uppals12-Apr-07 13:06
memberuppals12-Apr-07 13:06 
GeneralHelp needed Windows 2000 SP4 still getting 1314! -- Re: Error 1314 Pin
devvvy21-Feb-08 20:41
memberdevvvy21-Feb-08 20:41 
GeneralRe: Help needed Windows 2000 SP4 still getting 1314! -- Re: Error 1314 Pin
Marc Merritt26-Feb-08 3:02
memberMarc Merritt26-Feb-08 3:02 
Questionhow to use this in case of a local account? Pin
yossof elnaggar27-Jun-06 20:29
memberyossof elnaggar27-Jun-06 20:29 
AnswerRe: how to use this in case of a local account? Pin
hk1112-Jul-07 19:04
memberhk1112-Jul-07 19:04 
GeneralRe: how to use this in case of a local account? Pin
appalanaidu Aug20118-Feb-12 20:54
memberappalanaidu Aug20118-Feb-12 20:54 
GeneralFirst call takes too long Pin
schweeneh4-Apr-06 6:04
memberschweeneh4-Apr-06 6:04 
GeneralRe: First call takes too long Pin
Marc Merritt12-Jun-06 2:24
memberMarc Merritt12-Jun-06 2:24 
GeneralA similar article Pin
Uwe Keim23-Apr-05 23:59
sitebuilderUwe Keim23-Apr-05 23:59 
GeneralRe: A similar article Pin
craigg753-Nov-06 5:57
membercraigg753-Nov-06 5:57 
GeneralRe: A similar article Pin
Uwe Keim3-Nov-06 6:14
sitebuilderUwe Keim3-Nov-06 6:14 
GeneralImpersonation Pin
chriskoiak16-Mar-04 5:13
memberchriskoiak16-Mar-04 5:13 
QuestionRe: Impersonation Pin
tee_jay10-Apr-06 22:08
membertee_jay10-Apr-06 22:08 

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