Public Class AsynchDelegateForm
    Inherits System.Windows.Forms.Form
 
#Region " Windows Form Designer generated code "
 
    Public Sub New()
        MyBase.New()
 
        'This call is required by the Windows Form Designer.
        InitializeComponent()
 
        'Add any initialization after the InitializeComponent() call
 
    End Sub
 
    'Form overrides dispose to clean up the component list.
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub
 
    'Required by the Windows Form Designer
    Private components As System.ComponentModel.IContainer
 
    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer.  
    'Do not modify it using the code editor.
    Friend WithEvents StatusBar1 As System.Windows.Forms.StatusBar
    Friend WithEvents Label1 As System.Windows.Forms.Label
    Friend WithEvents TextBox1 As System.Windows.Forms.TextBox
    Friend WithEvents StartButton As System.Windows.Forms.Button
    Friend WithEvents CheckCompleteButton As System.Windows.Forms.Button
    Friend WithEvents GetResultButton As System.Windows.Forms.Button
    Friend WithEvents GetResultPollButton As System.Windows.Forms.Button
    Friend WithEvents UseCallbackCheckBox As System.Windows.Forms.CheckBox
    Friend WithEvents StartAndWaitButton As System.Windows.Forms.Button
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.StartButton = New System.Windows.Forms.Button
        Me.CheckCompleteButton = New System.Windows.Forms.Button
        Me.StatusBar1 = New System.Windows.Forms.StatusBar
        Me.Label1 = New System.Windows.Forms.Label
        Me.TextBox1 = New System.Windows.Forms.TextBox
        Me.GetResultButton = New System.Windows.Forms.Button
        Me.GetResultPollButton = New System.Windows.Forms.Button
        Me.UseCallbackCheckBox = New System.Windows.Forms.CheckBox
        Me.StartAndWaitButton = New System.Windows.Forms.Button
        Me.SuspendLayout()
        '
        'StartButton
        '
        Me.StartButton.Location = New System.Drawing.Point(24, 88)
        Me.StartButton.Name = "StartButton"
        Me.StartButton.Size = New System.Drawing.Size(80, 40)
        Me.StartButton.TabIndex = 0
        Me.StartButton.Text = "Start"
        '
        'CheckCompleteButton
        '
        Me.CheckCompleteButton.Location = New System.Drawing.Point(24, 184)
        Me.CheckCompleteButton.Name = "CheckCompleteButton"
        Me.CheckCompleteButton.Size = New System.Drawing.Size(80, 40)
        Me.CheckCompleteButton.TabIndex = 1
        Me.CheckCompleteButton.Text = "Check"
        '
        'StatusBar1
        '
        Me.StatusBar1.Location = New System.Drawing.Point(0, 245)
        Me.StatusBar1.Name = "StatusBar1"
        Me.StatusBar1.Size = New System.Drawing.Size(536, 16)
        Me.StatusBar1.TabIndex = 2
        '
        'Label1
        '
        Me.Label1.Location = New System.Drawing.Point(24, 8)
        Me.Label1.Name = "Label1"
        Me.Label1.Size = New System.Drawing.Size(104, 16)
        Me.Label1.TabIndex = 3
        Me.Label1.Text = "Time in seconds:"
        '
        'TextBox1
        '
        Me.TextBox1.Location = New System.Drawing.Point(24, 24)
        Me.TextBox1.Name = "TextBox1"
        Me.TextBox1.Size = New System.Drawing.Size(104, 20)
        Me.TextBox1.TabIndex = 4
        Me.TextBox1.Text = "TextBox1"
        '
        'GetResultButton
        '
        Me.GetResultButton.Location = New System.Drawing.Point(120, 88)
        Me.GetResultButton.Name = "GetResultButton"
        Me.GetResultButton.Size = New System.Drawing.Size(80, 40)
        Me.GetResultButton.TabIndex = 5
        Me.GetResultButton.Text = "Get result"
        '
        'GetResultPollButton
        '
        Me.GetResultPollButton.Location = New System.Drawing.Point(216, 88)
        Me.GetResultPollButton.Name = "GetResultPollButton"
        Me.GetResultPollButton.Size = New System.Drawing.Size(80, 40)
        Me.GetResultPollButton.TabIndex = 6
        Me.GetResultPollButton.Text = "Get result poll"
        '
        'UseCallbackCheckBox
        '
        Me.UseCallbackCheckBox.Checked = True
        Me.UseCallbackCheckBox.CheckState = _
          System.Windows.Forms.CheckState.Checked
        Me.UseCallbackCheckBox.Location = New System.Drawing.Point(24, 56)
        Me.UseCallbackCheckBox.Name = "UseCallbackCheckBox"
        Me.UseCallbackCheckBox.Size = New System.Drawing.Size(112, 16)
        Me.UseCallbackCheckBox.TabIndex = 7
        Me.UseCallbackCheckBox.Text = "Use callback"
        '
        'StartAndWaitButton
        '
        Me.StartAndWaitButton.Location = New System.Drawing.Point(24, 136)
        Me.StartAndWaitButton.Name = "StartAndWaitButton"
        Me.StartAndWaitButton.Size = New System.Drawing.Size(80, 40)
        Me.StartAndWaitButton.TabIndex = 8
        Me.StartAndWaitButton.Text = "Start and Wait"
        '
        'AsynchDelegateForm
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
        Me.ClientSize = New System.Drawing.Size(536, 261)
        Me.Controls.Add(Me.StartAndWaitButton)
        Me.Controls.Add(Me.UseCallbackCheckBox)
        Me.Controls.Add(Me.GetResultPollButton)
        Me.Controls.Add(Me.GetResultButton)
        Me.Controls.Add(Me.TextBox1)
        Me.Controls.Add(Me.Label1)
        Me.Controls.Add(Me.StatusBar1)
        Me.Controls.Add(Me.CheckCompleteButton)
        Me.Controls.Add(Me.StartButton)
        Me.Name = "AsynchDelegateForm"
        Me.Text = "AsynchDelegateForm"
        Me.ResumeLayout(False)
 
    End Sub
 
#End Region
 
    ' Delegate for DoSomethingTakingALongTime() signature
    Private Delegate Function DoSomethingTakingALongTimeDelegate(ByVal ssecs As _
      Integer) As String
 
    ' Delegate for SetStatusText() signature
    Private Delegate Sub SetStatusTextDelegate(ByVal t As String)
 
    ' Delegate object for asynch calls
    Private exec As New DoSomethingTakingALongTimeDelegate(AddressOf _
      DoSomethingTakingALongTime)
 
    ' Asynchronous Call Result
    Private execRes As IAsyncResult
 
    ' Shows callback active (in case user changes checkbox)
    Private cbactive As Boolean
 
    ' Shows waiting in DoEvents loop
    Private waiting As Boolean
 
    ' The routine to be called asynchronously
    Private Function DoSomethingTakingALongTime(ByVal secs As Integer) As String
        System.Threading.Thread.Sleep(secs * 1000)
        Return "Some value from DoSomethingTakingALongTime"
    End Function
 
    ' The Asynchronous result callback routine
    Private Sub DoSomethingTakingALongTimeCallBack(ByVal ar As IAsyncResult)
        Dim resp As String = exec.EndInvoke(ar)
        Me.Invoke(New SetStatusTextDelegate(AddressOf SetStatusText), New _
          Object() {"Call completed: " + resp + " (asynch)"})
        execRes = Nothing
        cbactive = False
    End Sub
 
    ' Start asynch call
    Private Sub StartButton_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles StartButton.Click
        If execRes Is Nothing Then
            StatusBar1.Text = "Call started"
            If UseCallbackCheckBox.Checked Then
                cbactive = True
                execRes = exec.BeginInvoke(CInt(TextBox1.Text), AddressOf _
                  DoSomethingTakingALongTimeCallBack, Nothing)
            Else
                execRes = exec.BeginInvoke(CInt(TextBox1.Text), Nothing, _
                  Nothing)
            End If
        Else
            SetStatusText("Call is already active")
        End If
    End Sub
 
    ' Check completion
    Private Sub CheckCompleteButton_Click(ByVal sender As System.Object, ByVal _
      e As System.EventArgs) Handles CheckCompleteButton.Click
        If execRes Is Nothing Then
            StatusBar1.Text = "Call completed"
        Else
            StatusBar1.Text = "Call not completed"
        End If
    End Sub
 
    ' Wait for and get result 
    Private Sub GetResultButton_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles GetResultButton.Click
        If checkstatus() Then Return
 
        ' Call will wait until asynch completiom
        Dim resp As String = exec.EndInvoke(execRes)
        StatusBar1.Text = "Call completed: " + resp
        execRes = Nothing
    End Sub
 
    ' Get result by polling until finished
    Private Sub GetResultPollButton_Click(ByVal sender As System.Object, ByVal _
      e As System.EventArgs) Handles GetResultPollButton.Click
        If checkstatus() Then Return
 
        ' Stop strange form behaviour due to mouse capture
        GetResultPollButton.Capture = False
 
        ' Wait in DoEvents loop until asynch completion
        waiting = True
        Do While Not execRes.IsCompleted
            Application.DoEvents()
            System.Threading.Thread.Sleep(50)
        Loop
        waiting = False
 
        ' Now result is present
        Dim resp As String = exec.EndInvoke(execRes)
        StatusBar1.Text = "Call completed: " + resp
        execRes = Nothing
    End Sub
 
    ' Start and wait
    Private Sub StartAndWaitButton_Click(ByVal sender As System.Object, ByVal e _
      As System.EventArgs) Handles StartAndWaitButton.Click
        If execRes Is Nothing Then
            If UseCallbackCheckBox.Checked Then
                StatusBar1.Text = "Cannot perform start and wait with callback" & _
                  "option set"
                Return
            End If
            StatusBar1.Text = "Call started"
            execRes = exec.BeginInvoke(CInt(TextBox1.Text), Nothing, Nothing)
 
            ' Stop strange form behaviour due to mouse capture
            StartAndWaitButton.Capture = False
 
            ' Wait in DoEvents loop until asynch completion
            waiting = True
            Do While Not execRes.IsCompleted
                Application.DoEvents()
                System.Threading.Thread.Sleep(50)
            Loop
            waiting = False
 
            ' Now result is present
            Dim resp As String = exec.EndInvoke(execRes)
            StatusBar1.Text = "Call completed: " + resp
            execRes = Nothing
        Else
            SetStatusText("Call is already active")
        End If
    End Sub
 
    ' Check status for get result buttons
    Private Function checkstatus() As Boolean
        If waiting Or cbactive Then
            StatusBar1.Text = "Application waiting for asynch result"
            Return True
        End If
        If execRes Is Nothing Then
            StatusBar1.Text = "No call active"
            Return True
        End If
    End Function
 
    ' Routine to set statusbar text (for delegate)
    Private Sub SetStatusText(ByVal t As String)
        StatusBar1.Text = t
    End Sub
 
    ' Init 
    Private Sub AsynchDelegateForm_Load(ByVal sender As System.Object, ByVal e _
      As System.EventArgs) Handles MyBase.Load
        TextBox1.Text = "15"
    End Sub
 
End Class

________
Alle Angaben ohne Gewähr. Keine Haftung für Vorschläge, Tipps oder sonstige Hilfe, falls es schiefgeht, nur Zeit verschwendet oder man sonst nicht zufrieden ist