Faster way to find out if a user exists on a system?

Question

I have an application that checks to see if a user exists (if not create it) every time it starts. This is done as follows:

bool bUserExists = false;
Directo         


        

Answer 1

.NET 3.5 supports new AD querying classes under the System.DirectoryServices.AccountManagement namespace.

To make use of it, you'll need to add "System.DirectoryServices.AccountManagement" as a reference AND add the using statement.

using System.DirectoryServices.AccountManagement;


using (PrincipalContext pc = new PrincipalContext(ContextType.Machine))
{
    UserPrincipal up = UserPrincipal.FindByIdentity(
        pc,
        IdentityType.SamAccountName,
        "UserName");

    bool UserExists = (up != null);
}

< .NET 3.5

For versions of .NET prior to 3.5, here is a clean example I found on dotnet-snippets

DirectoryEntry dirEntryLocalMachine =
    new DirectoryEntry("WinNT://" + Environment.MachineName + ",computer");

bool UserExists =
    dirEntryLocalMachine.Children.Find(userIdentity, "user") != null;

Answer 2

You want to use the DirectorySearcher.

Something like this:

static bool userexists( string strUserName ) {
    string adsPath = string.Format( @"WinNT://{0}", System.Environment.MachineName );
    using( DirectoryEntry de = new DirectoryEntry( adsPath ) ) {
        try {
            return de.Children.Find( strUserName ) != null;
        } catch( Exception e ) {
            return false;
        }
    }
}

That should be quicker. Also, you can reduce the properties if all you are doing is checking for existence.

Answer 3

The following in a command prompt returns 1 if 'username' exists.

net user | find "username" /c

Answer 4

This should do it (when you can't use System.DirectoryServices.AccountManagement):

static bool userExists(string sUser)
{
    using (var oUser = new DirectoryEntry("WinNT://" + Environment.MachineName + "/" + sUser + ",user")) 
    {
         return (oUser != null);
    }
}