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Posted 11 Apr 2005
Licenced CPOL

A small C# Class for impersonating a User

, 11 Apr 2005
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Introduced a class that simplifies Windows Impersonation in C#.


The term "Impersonation" in a programming context refers to a technique that executes the code under another user context than the user who originally started an application, i.e. the user context is temporarily changed once or multiple times during the execution of an application.

The reason for doing this is to perform tasks that the current user context of an application is not allowed to do. Of course you could grant the user executing an application more privileges, but usually this is a bad idea (due to security constraints) or impossible (e.g. if you don't have full administrative access to a machine to do so).

This article presents an easy-to-use class to impersonate a user. While writing this, I found out that Marc Merrit had written an article ("Windows Impersonation using C#") that uses the same Microsoft knowledge base code (from Q306158) that I have used. The code presented in my article differs in the fact that you could use it inside a using-block to safely release resources and that I use slightly more exceptions to report errors. But from a first look, both his and my article do the same job, so it's up to you to decide what to do.

(For the latest changes, please see the History section below).


I wrote the Impersonator class because of a need to write a web page with ASP.NET to make a server reboot. In order to do this, I needed to impersonate the part of my code that does the actual reboot.

The constructor of the class internally calls the Windows function LogonUser through P/Invoke. Please see the MSDN documentation of the function for a full description of all three parameters (username, domain, password) to the constructor.

Please note: The user context that initiates the impersonation (i.e. not the user context to which it is switched to) needs to have the "Act as part of operating system" privilege set.

Using the code

To use the code, you simply construct the Impersonator class and pass the username, the domain and the password to the constructor. If you place an instance of the class inside a using-block, you need no further steps.

The following is a schematic example of how to use the class:

using ( new Impersonator( "myUsername", "myDomainname", "myPassword" ) )
   <code that executes under the new context>

An example project demonstrating the technique is included in the download of this article (please look at the "Program.cs" for the main demonstration source file). Also the complete source code of the class is included inside the source file "Impersonator.cs".

To include the Impersonator class into your project, simply copy and add the source file "Impersonator.cs" to your project, so that it gets compiled with your project.


In this article, I've shown you a small class to quickly and easily impersonate a part of your code to run under another user context. Hopefully you'll find this class useful.

For questions, comments and remarks, please use the commenting section at the bottom of this article.


In addition to the links in the article, the following references might be of interest:

  1. Google search for "Windows Impersonation"


  • 2005-04-11: Created first version of article.


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


About the Author

Uwe Keim
Chief Technology Officer Zeta Producer Desktop CMS
Germany Germany
Uwe does programming since 1989 with experiences in Assembler, C++, MFC and lots of web- and database stuff and now uses ASP.NET and C# extensively, too. He has also teached programming to students at the local university.

In his free time, he does climbing, running and mountain biking. Recently he became a father of a cute boy.

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Comments and Discussions

GeneralRe: Does not work for remote local accounts Pin
Uwe Keim13-Mar-08 19:01
sitebuilderUwe Keim13-Mar-08 19:01 
GeneralRe: Does not work for remote local accounts Pin
D Waterworth29-May-08 13:36
memberD Waterworth29-May-08 13:36 
QuestionRe: Does not work for remote local accounts Pin
A_Mano28-Jul-08 9:39
memberA_Mano28-Jul-08 9:39 
GeneralGetting invalid logon [modified] Pin
deerinb23-Jan-08 10:26
memberdeerinb23-Jan-08 10:26 
GeneralUnfortunately doesn't work in Pin
vytas z.12-Dec-07 1:35
membervytas z.12-Dec-07 1:35 
GeneralRe: Unfortunately doesn't work in Pin
Chris Maunder8-Jan-08 1:00
adminChris Maunder8-Jan-08 1:00 
GeneralSimple, Easy and working properly.... Pin
Ricardo Casquete10-Dec-07 10:53
memberRicardo Casquete10-Dec-07 10:53 
GeneralConverted to VB.NET Pin
Zyxil9-Nov-07 7:45
memberZyxil9-Nov-07 7:45 
QuestionImpersonator and DSOFile Pin
Daniele Perilli7-Nov-07 23:46
memberDaniele Perilli7-Nov-07 23:46 
GeneralThanks! Pin
boo13-Oct-07 14:12
memberboo13-Oct-07 14:12 
GeneralRe: Thanks! Pin
Uwe Keim13-Oct-07 20:23
sitebuilderUwe Keim13-Oct-07 20:23 
QuestionCreateProcessWithTokenW Pin
Harkamal Singh16-Jul-07 5:47
memberHarkamal Singh16-Jul-07 5:47 
GeneralImpersonation in ASPNET not working Pin
Talal Sultan4-Jun-07 3:46
memberTalal Sultan4-Jun-07 3:46 
QuestionTested on Vista? Pin
Neil Baliga2-Jun-07 17:19
memberNeil Baliga2-Jun-07 17:19 
AnswerRe: Tested on Vista? Pin
Uwe Keim2-Jun-07 19:37
sitebuilderUwe Keim2-Jun-07 19:37 
AnswerRe: Tested on Vista? Pin
rob.iles21-Feb-08 20:05
memberrob.iles21-Feb-08 20:05 
GeneralRe: Tested on Vista? Pin
Uwe Keim22-Feb-08 2:39
sitebuilderUwe Keim22-Feb-08 2:39 
GeneralRe: Tested on Vista? Pin
rob.iles22-Feb-08 2:48
memberrob.iles22-Feb-08 2:48 
AnswerRe: Tested on Vista? Pin
Uwe Eichkorn5-Mar-08 0:01
memberUwe Eichkorn5-Mar-08 0:01 
GeneralRe: Tested on Vista? Pin
ru551an9-Apr-08 12:47
memberru551an9-Apr-08 12:47 
GeneralError when compiling code [modified] Pin
cpltek14-Mar-07 9:07
membercpltek14-Mar-07 9:07 
GeneralRe: Error when compiling code Pin
Eradikator26-Mar-07 0:11
memberEradikator26-Mar-07 0:11 
GeneralRe: Error when compiling code Pin
cpltek26-Mar-07 8:54
membercpltek26-Mar-07 8:54 
Questionhow to create file in denyaccess folder using c# Pin
Member 38880247-Mar-07 1:49
memberMember 38880247-Mar-07 1:49 
QuestionI still have the same problem Pin
Vince Zhou21-Feb-07 14:27
memberVince Zhou21-Feb-07 14:27 

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