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Posted 19 May 2002


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Get The User Name In C# For NT Authentication

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4.80/5 (33 votes)
20 May 20022 min read
Through the .NET Framework you can easily get the current user name to authenticate.


Our department has recently begun moving all of our Client/Server Applications over to Windows NT authentication via Active Directory. Our previous applications used a SQL Server login for each user. This can become very tedious when it come to setting up users across the company for wide spread applications. There are also inherent security risks involved without the user being authenticated. I thought I would share the following code dealing with security in .NET in hopes that it will help someone else.

Our applications are done in Visual Basic, so we of course have to make a Windows API call where we have defined the following function:

Old VB6 Windows API Method Call

Declare Function GetUserName Lib "advapi32.dll" Alias _
                "GetUserNameA" (ByVal lpBuffer As String, nSize As Long) As Long

This is not difficult at all, however I have been playing around with C# lately and I thought it would be interesting to find out how we will do this in managed code.

My first idea was to do an import of the above mentioned advapi32.dll along with the method we will use to get the user name. There have been many other examples on Code Project where users have imported methods through existing .dll's, so hopefully some of this looks familiar. I have tried to document what is going on here, even though it is rather simple. The following code will require you to add using statement as well.

Possible New C# Managed Method

//Include at the top, above the namespace declaration.

using System.Runtime.InteropServices;

//Defines the .dll file to import as well as the method 
//to use.

[DllImport("Advapi32.dll", EntryPoint="GetUserName", 
		ExactSpelling=false, SetLastError=true)]

//This specifies the exact method we are going to call 
//from within our imported .dll

static extern bool GetUserName(
	[MarshalAs(UnmanagedType.LPArray)] byte[] lpBuffer,
	[MarshalAs(UnmanagedType.LPArray)] Int32[] nSize );

//The following is the implementation of our imported 

	byte[] str=new byte[256];
	Int32[] len=new Int32[1];

What I thought was an instant solution actually made me think a little harder about my initial problem. There must be a better way to get the username than by making an old Windows API call. Upon doing a little research I have come to the conclusion that the boys over at Microsoft did manage to include this into the .NET Framework rather seamlessly. I was rather shocked when I found out how very simple it was. You will only need the following:

Most Sensible C# Method

//Place this at the top, above your namespace declaration

using System.Security.Principal;

//In a specific event, place the following.

string a;
a = System.Security.Principal.WindowsIdentity.GetCurrent().Name.ToString();

The System.Security.Principal.WindowsIdentity.GetCurrent() section opens us up to more than just the current user. When looking you will find the following additional methods/properties within this section of the .NET Framework:
  • AuthenticationType - Get's the type of authentication used to authenticate the user.
  • Impersonates - Impersonates the user represented by the object.
  • IsAnonymous - Indicates whether the user account is identified as an anonymous account by the system.
  • IsAuthenticated - Determines if the user has been authenticated by Windows.
  • IsGuest - Indicates whether the account is defined as a guest account by the system.
  • IsSystem - Indicates whether the account is defined as a system account by the system.
That’s it! There isn’t a whole lot to it and we don’t even have to do any of the ugly importation of old .dll’s. Hope this helps someone, I found it to be rather interesting.


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About the Author

Nick Parker
Software Developer (Senior)
United States United States
Nick graduated from Iowa State University with a B.S. in Management Information System and a minor in Computer Science. Nick works for Zetetic.

Nick has also been involved with the Iowa .NET User Group since it's inception, in particular giving presentations over various .NET topics. Nick was awarded the Visual C# MVP award from Microsoft for four years in a row.

In his mystical spare time he is working on a development project called "DeveloperNotes" which integrates into Visual Studio .NET allowing developers easy access to common code pieces. He is also a fan of using dynamically typed languages to perform unit testing, not to mention how he loves to talk about himself in the third person.

Comments and Discussions

GeneralMy vote of 1 Pin
aankss221-Feb-12 23:27
Memberaankss221-Feb-12 23:27 
GeneralThanx! Pin
WarmBlanke11-Nov-09 2:44
MemberWarmBlanke11-Nov-09 2:44 
QuestionHow to create database that contains users Pin
sanshine198723-Jul-09 4:16
Membersanshine198723-Jul-09 4:16 
GeneralThanks Pin
irshadmohideen17-Jun-09 1:01
Memberirshadmohideen17-Jun-09 1:01 
GeneralGet the user name against a published application Pin
btalaman22-Mar-09 9:48
Memberbtalaman22-Mar-09 9:48 
QuestionCan not get username in window server 2003 Pin
hkim_zoro6-Feb-09 15:04
Memberhkim_zoro6-Feb-09 15:04 
AnswerRe: Can not get username in window server 2003 Pin
Nick Parker6-Feb-09 15:41
protectorNick Parker6-Feb-09 15:41 
GeneralRe: Can not get username in window server 2003 Pin
hkim_zoro6-Feb-09 15:54
Memberhkim_zoro6-Feb-09 15:54 
GeneralRe: Can not get username in window server 2003 Pin
Craig C.6-Mar-09 8:39
MemberCraig C.6-Mar-09 8:39 
GeneralRe: Can not get username in window server 2003 [modified] Pin
antonu21-Dec-09 23:04
Memberantonu21-Dec-09 23:04 
QuestionAPI Method Call Declare Function VBA to C# Question! Pin
andredani25-Aug-08 3:30
Memberandredani25-Aug-08 3:30 
GeneralVery useful Pin
Cliff Stanford5-Jun-08 3:38
MemberCliff Stanford5-Jun-08 3:38 
GeneralQurey Active directory with the login id to get the user Name Pin
rozhanin30-Mar-08 23:55
Memberrozhanin30-Mar-08 23:55 
Generallogged on user vs. currently executing user Pin
nitstheone27-Mar-08 6:43
Membernitstheone27-Mar-08 6:43 
GeneralRemote Username Pin
crouchie0412-May-07 12:52
Membercrouchie0412-May-07 12:52 
QuestionRetrieve login user's password Pin
Biswajit Ghosh3-Apr-07 20:04
MemberBiswajit Ghosh3-Apr-07 20:04 
AnswerRe: Retrieve login user's password Pin
Nick Parker4-Apr-07 3:31
protectorNick Parker4-Apr-07 3:31 
GeneralRe: Retrieve login user's password Pin
Biswajit Ghosh4-Apr-07 18:50
MemberBiswajit Ghosh4-Apr-07 18:50 
GeneralRe: Retrieve login user's password Pin
keych22-Aug-07 3:41
Memberkeych22-Aug-07 3:41 
GeneralHi there! Pin
krishna nimmalapudi25-Apr-06 9:49
Memberkrishna nimmalapudi25-Apr-06 9:49 
GeneralRe: Hi there! Pin
Nick Parker25-Apr-06 12:03
protectorNick Parker25-Apr-06 12:03 
GeneralReturns Machine Name Pin
Clank22-Jun-05 4:05
MemberClank22-Jun-05 4:05 
GeneralRe: Returns Machine Name Pin
jklucker22-Jun-05 7:27
Memberjklucker22-Jun-05 7:27 
GeneralRe: Returns Machine Name Pin
Clank22-Jun-05 7:57
MemberClank22-Jun-05 7:57 
GeneralRe: Returns Machine Name Pin
smaxwell12-Aug-05 11:49
Membersmaxwell12-Aug-05 11:49 

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