Get The User Name In C# For NT Authentication

• Download source files/demo project - 16 Kb

Introduction

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 
//method.

	byte[] str=new byte[256];
	Int32[] len=new Int32[1];
	len[0]=256;
	GetUserName(str,len);      
	MessageBox.Show(System.Text.Encoding.ASCII.GetString(str));

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();

MessageBox.Show(a.ToString());

• 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.

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