/// The system function, LookupAccountName, failed

        LookupAccountName(Nothing, _UserName, Nothing, lenSid, Nothing, lenDomain, peUse)

        If LookupAccountName(Nothing, _UserName, pSID, lenSid, Domain, lenDomain, peUse) = False Then

    class clsLookupAccountName

    static extern bool LookupAccountName(

        if (!LookupAccountName(null,accountName,Sid,ref cbSid,referencedDomainName,ref cchReferencedDomainName,out sidUse))

            if (!LookupAccountName(null,accountName,Sid,ref cbSid,referencedDomainName,ref cchReferencedDomainName,out sidUse))

static extern bool LookupAccountName (

Private Shared Function LookupAccountName(lpSystemName As String, lpAccountName As String, <MarshalAs(UnmanagedType.LPArray)> Sid As Byte(), ByRef cbSid As UInteger, ReferencedDomainName As StringBuilder, ByRef cchReferencedDomainName As UInteger, peUse As SID_NAME_USE) As Boolean

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.

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.

    class clsLookupAccountName

        static extern bool LookupAccountName (

            if (!LookupAccountName(null,accountName,Sid,ref cbSid,referencedDomainName,ref cchReferencedDomainName,out sidUse))

                    if (!LookupAccountName(null,accountName,Sid,ref cbSid,referencedDomainName,ref cchReferencedDomainName,out sidUse))

    ret = LookupAccountName(Nothing, UserName, Nothing, cbSid, Nothing, cbRefDomainName, peUse)

    ret = LookupAccountName(Nothing, UserName, ptrSid, cbSid, refDomainName, cbRefDomainName, peUse)

    LookupAccountName( String.Empty, inAccountName, aSid, ref aSidSize, aDomainName, ref aNameSize, ref aAccountType );

    bool aResult = LookupAccountName( String.Empty, inAccountName, aSid, ref aSidSize, aDomainName, ref aNameSize, ref aAccountType );

        if (!LookupAccountName(this.ResourceName, this.UserName, Sid, ref cbSid, referencedDomainName, ref cchReferencedDomainName, out sidUse))

            if (!LookupAccountName(this.ResourceName, this.UserName, Sid, ref cbSid, referencedDomainName, ref cchReferencedDomainName, out sidUse))

    ///The system function, LookupAccountName, failed

    [Description("The system function, LookupAccountName, failed")]

    '''The system function, LookupAccountName, failed

    <Description("The system function, LookupAccountName, failed")> _