C# Signature:

  [DllImport( "advapi32.dll", CharSet=CharSet.Auto, SetLastError=true, PreserveSig=true)]
  private static extern bool LookupAccountName(
    string lpSystemName,
    string lpAccountName,
    IntPtr psid,
    ref int cbsid,
    StringBuilder domainName,    //StringBuilder or string?
    ref int cbdomainLength,
    ref int use );

VB .NET Signature:

Declare Function LookupAccountName Lib "advapi32.dll" (TODO) As TODO

User-Defined Types:

None.

Notes:

From the SDK:

The LookupAccountName function attempts to find a SID for the specified name by first checking a list of well-known SIDs. If the name does not correspond to a well-known SID, the function checks built-in and administratively defined local accounts. Next, the function checks the primary domain. If the name is not found there, trusted domains are checked.

Use fully qualified account names (for example, domain_name\user_name) instead of isolated names (for example, user_name). Fully qualified names are unambiguous and provide better performance when the lookup is performed. This function also supports fully qualified DNS names (for example, example.example.com\user_name) and user principal names (UPN) (for example, someone@example.com).

Windows NT: DNS and UPN names are not supported by this function.

In addition to looking up local accounts, local domain accounts, and explicitly trusted domain accounts, LookupAccountName can look up the name for any account in any domain in the forest.

Windows NT: Forest lookup is not supported.

Tips & Tricks:

Please add some!

Sample Code:

using System;

using System.Runtime.InteropServices;

using System.Text;

class Test

{

  static void Main()  {
    string strSid = GetSIDForAccount("Administrator");
    Console.WriteLine( strSid  );
  }

  public static string GetSIDForAccount(string Account) {
    long winErrorCode = 0; //contains the last error

    //pointer and size for the SID
    IntPtr pSid = IntPtr.Zero;
    int iSidSize = 0;
    //StringBuilder for Domain
    StringBuilder sbDomain = new StringBuilder();
    int iDomainSize = 0;

    //account-type variable for lookup
    int iAccountType = 0;

    //get required buffer size  (iSidSize=0 causes this...)
    LookupAccountName(String.Empty, Account, pSid, ref iSidSize,
      sbDomain, ref iDomainSize, ref iAccountType);

    //allocate buffers
    sbDomain = new StringBuilder(iDomainSize);
    pSid = Marshal.AllocHGlobal(iSidSize);

    //lookup the SID for the account
    bool bResult = LookupAccountName(String.Empty,
                     Account,
                     pSid,
                     ref iSidSize,
                     sbDomain,
                     ref iDomainSize,
                     ref iAccountType);
    if (!bResult) {
      winErrorCode = GetLastError();
      Console.WriteLine("LookupAccountName failed: "+ winErrorCode);
      FreeSid(pSid);
      throw new ApplicationException("Could not read SID");
    }

    string strSID = "";
    if ( ConvertSidToStringSid( pSid, ref strSID)) {
      FreeSid(pSid);
      return strSID;
    } else {
      throw new ApplicationException("Could not convert SID");
    }
  }

  [DllImport("kernel32.dll")]
  private static extern int GetLastError();

  [DllImport( "advapi32.dll", CharSet=CharSet.Auto, SetLastError=true, PreserveSig=true)]
  private static extern bool LookupAccountName(
    string lpSystemName,
    string lpAccountName,
    IntPtr psid,
    ref int cbsid,
    StringBuilder domainName,    //StringBuilder or string?
    ref int cbdomainLength,
    ref int use );

  [DllImport("advapi32.dll", CharSet=CharSet.Auto)]
  private static extern bool ConvertSidToStringSid(
    IntPtr pSID,
    [In,Out,MarshalAs(UnmanagedType.LPTStr)] ref string strSID);

  [DllImport("advapi32")]
  private static extern void FreeSid(IntPtr pSid);  

}

Alternative Managed API:

TODO

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