VB.NETでPDFファイルをAcrobatを使用して非同期印刷する

printerName = 印刷するプリンター名
acrobatPath = Acrobatのexeファイルへのパス
filePathList = 印刷するPDFファイルへのパスのList
processList As List(Of ProcessInfo)

'ProcessInfoクラス 複数の process を管理するため作成
Private Class ProcessInfo
        Public Property Process As Process
        Public ReadOnly Property Filename As String
        Public Property HasExited As Boolean
        Public Property ErrorMsg As String
    Public Sub New(process As Process, filename As String)
        Me.Process = process
        Me.Filename = filename
        
        HasExited = False
    End Sub
End Class

'Module1.main
Dim printerSettings As New PrinterSettings()
For Each printer As String In PrinterSettings.InstalledPrinters
    If printer = printerName Then
        Return True
    End If
Next
Return False

'Module1.main
For Each filePath As String In filePathList
    'すこしsleepする
    Thread.Sleep(1000)
    PrintPdfAsync(filePath)
Next

'Module1.main
'Imports System.Windows.Forms
Application.Run()

'Module1
Private Sub PrintPdfAsync(filePath As String)
    Task.Run(Sub()
        Dim result = PrintPdfClass.PrintPdf(filePath)
        If Not result Then
            ' PrintPdfがFalseを返した場合、アプリケーションを終了する
            PrintPdfClass.Dispose()
            Environment.Exit(0)
        End If
    End Sub)
End Sub

'PrintPdfClass
Public Function PrintPdf(filePath As String) As Boolean
    Dim printArgs As String = String.Format("/h /t ""{0}"" ""{1}""", filePath,    printerName)
    ' Acrobat Readerを起動してPDFファイルを印刷する
    Dim processInfo As New ProcessStartInfo(acrobatPath, printArgs)
    processInfo.CreateNoWindow = True
    processInfo.WindowStyle = ProcessWindowStyle.Hidden
    Dim process = New Process With {
        .EnableRaisingEvents = True,
        .StartInfo = processInfo
    }
    AddHandler process.Exited, AddressOf ProcessExited
    Dim processInfoClass As New ProcessInfo(process, filePath)
    processList.Add(processInfoClass)
    process.Start()
    Return True
End Function

'PrintPdfClass
'Acrobatのウィンドウを閉じるときに使用する
Private Declare Function FindWindow Lib "user32.dll" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As IntPtr
Private Declare Function SendMessage Lib "user32.dll" Alias "SendMessageA" (ByVal hWnd As IntPtr, ByVal wMsg As Integer, ByVal wParam As Integer, ByVal lParam As Integer) As Integer
Private Const WM_SYSCOMMAND As Integer = &H112
Private Const SC_CLOSE As Integer = &HF060
Private Sub ProcessExited(sender As Object, e As EventArgs)
    Dim exitedProcess As Process = CType(sender, Process)
    exitedProcess.Dispose()
    'すべてのプロセスが終了した場合のIf内で
    ' Acrobat Readerのウィンドウを閉じる処理を非同期に実行する
    Task.Run(
        Sub()
            ' Acrobat Readerのウィンドウを探す
            Dim adobeWindowHandle As IntPtr = IntPtr.Zero
            Do Until adobeWindowHandle <> IntPtr.Zero
                adobeWindowHandle = FindWindow("AcrobatSDIWindow", vbNullString)
            Loop
        　　' Acrobat Readerのウィンドウを閉じる
            SendMessage(adobeWindowHandle, WM_SYSCOMMAND, SC_CLOSE, 0)
        End Sub
    )
End Sub

Public Sub Dispose()
    For Each processInfo In processList
        processInfo.Process.Dispose()
    Next
End Sub