C# と VB.NET の質問掲示板

OpenPrinterを使ってもプリンタのハンドルが取得できません。
なぜでしょうか？
下記のように書いてあります。

    Public Const SERVER_ACCESS_ADMINISTER As Integer = 1

    Public Structure PRINTER_DEFAULTS
        Public pDatatype As IntPtr
        Public pDevMode As IntPtr
        Public DesiredAccess As Integer
    End Structure

    <DllImport("winspool.drv", EntryPoint:="OpenPrinterA", ExactSpelling:=True, _
           SetLastError:=True, CallingConvention:=CallingConvention.StdCall, _
           CharSet:=CharSet.Ansi)> _
    Public Function OpenPrinter( _
    <InAttribute()> ByVal pPrinterName As String, _
    <OutAttribute()> ByRef hPrinter As IntPtr, _
    <InAttribute()> ByRef pDefault As PRINTER_DEFAULTS) As Boolean
    End Function

        Dim Status As Boolean

        Dim PrinterName As String = "RICOH imagio MP C4500 RPCS"
        Dim hPrinter As IntPtr
        Dim pDefault As PRINTER_DEFAULTS


        pDefault.pDatatype = IntPtr.Zero
        pDefault.pDevMode = IntPtr.Zero
        pDefault.DesiredAccess = SERVER_ACCESS_ADMINISTER

        Status = OpenPrinter(PrinterName, hPrinter, pDefault)