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

DirectoryEntries dirEntries = dirEntryLocalMachine.Children;

foreach (DirectoryEntry dirEntryUser in dirEntries)
{
    bUserExists = dirEntryUser.Name.Equals("UserName", 
     StringComparison.CurrentCultureIgnoreCase);

    if (bUserExists)
      break;
}

Problem is on the majority of the systems where it is deployed this can take 6 - 10 seconds, which is too long ... I need to find a way to reduce this (as much as possible). So is there a BETTER or FASTER way I can use to verify if a user exists on the system or not?

I know there are other ways to solve this, like have the other applications sleep for 10 seconds, or have this tool send a message when he is ready, etc... but if I can greatly reduce the time it takes to find the user it would make my life much easier.

Any help would be greatly appreciated. Thanks,

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

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

net user | find "username" /c

Answer 3

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 existance.