VB.net creating new AD user account using UserPrincipalEx?

If you're on .NET 3.5 and up, you should check out the System.DirectoryServices.AccountManagement (S.DS.AM) namespace. Read all about it here:

• Managing Directory Security Principals in the .NET Framework 3.5
• MSDN docs on System.DirectoryServices.AccountManagement

To extend the UserPrincipal class, you don't need much - something like this will suffice (I wrote this in C# originally and just converted it to VB.NET on the 'net - I hope there's no issues with the VB.NET code!)

Imports System.DirectoryServices.AccountManagement

Namespace ADExtended
    <DirectoryRdnPrefix("CN")> _
    <DirectoryObjectClass("Person")> _
    Public Class UserPrincipalEx
        Inherits UserPrincipal
        ' Inplement the constructor using the base class constructor. 
        Public Sub New(context As PrincipalContext)
            MyBase.New(context)
        End Sub

        ' Implement the constructor with initialization parameters.    
        Public Sub New(context As PrincipalContext, samAccountName As String, password As String, enabled As Boolean)
            MyBase.New(context, samAccountName, password, enabled)
        End Sub

        ' Create the "Department" property.    
        <DirectoryProperty("department")> _
        Public Property Department() As String
            Get
                If ExtensionGet("department").Length <> 1 Then
                    Return String.Empty
                End If

                Return DirectCast(ExtensionGet("department")(0), String)
            End Get
            Set
                ExtensionSet("department", value)
            End Set
        End Property

        ' Create the "Title" property.    
        <DirectoryProperty("title")> _
        Public Property Title() As String
            Get
                If ExtensionGet("title").Length <> 1 Then
                    Return String.Empty
                End If

                Return DirectCast(ExtensionGet("title")(0), String)
            End Get
            Set
                ExtensionSet("title", value)
            End Set
        End Property

        ' Implement the overloaded search method FindByIdentity.
        Public Shared Shadows Function FindByIdentity(context As PrincipalContext, identityValue As String) As UserPrincipalEx
            Return DirectCast(FindByIdentityWithType(context, GetType(UserPrincipalEx), identityValue), UserPrincipalEx)
        End Function

        ' Implement the overloaded search method FindByIdentity. 
        Public Shared Shadows Function FindByIdentity(context As PrincipalContext, identityType As IdentityType, identityValue As String) As UserPrincipalEx
            Return DirectCast(FindByIdentityWithType(context, GetType(UserPrincipalEx), identityType, identityValue), UserPrincipalEx)
        End Function
    End Class
End Namespace

Now, you just use the UserPrincipalEx class:

Dim ctx As New PrincipalContext(ContextType.Domain, "domain.name.pvt",  "OU=Users,DC=global,DC=pvt")

Dim usr As UserPrincipalEx = New UserPrincipalEx(ctx) 
usr.Title = "......."
usr.Department = "......."

The new S.DS.AM makes it really easy to play around with users and groups in AD!