HOW TO：在共用執行緒上顯示 Windows Form 以支援 COM Interop

發行項
05/17/2010

您可以在使用 Application.Run 方法所建立的 .NET Framework 訊息迴圈上顯示表單，藉此解決元件物件模型 (Component Object Model，COM) 的互通性問題。

若要使 Windows Form 能從 COM 用戶端應用程式正確運作，您就必須在 Windows Form 訊息迴圈中執行 Windows Form。若要這麼做，請使用下列其中一種方法：

您可以使用 Form.ShowDialog 方法來顯示 Windows Form。如需詳細資訊，請參閱 HOW TO：顯示 Windows Form 和 ShowDialog 方法以支援 COM Interop。
在新的執行緒上顯示每一個 Windows Form。如需詳細資訊，請參閱 HOW TO：在自己的執行緒上顯示每個 Windows Form 以支援 COM Interop。
在 .NET Framework 元件中的新執行緒上建立共用的訊息迴圈。

下列程式碼範例示範如何使用共用訊息迴圈在新執行緒上顯示 Windows Form。

在 Visual Studio 中對此功能有相當廣泛的支援。

範例

在共用執行緒上顯示 Windows Form 類似於在 HOW TO：在自己的執行緒上顯示每個 Windows Form 以支援 COM Interop 中所示範的方法。但是，您建立的共用訊息迴圈只會在 .NET Framework 元件中的一個新執行緒上執行，而不是讓每個表單使用自己的訊息迴圈在自己的執行緒上顯示。

這個方法會更正確地顯示標準 Windows Form 應用程式的行為。它也可以讓您更輕鬆地在多個表單間共用資源，因為所有表單都是在相同的執行緒上執行。 HOW TO：在自己的執行緒上顯示每個 Windows Form 以支援 COM Interop 中的方案會為每個表單建立新的執行緒。這個方案需要其他執行緒同步處理程式碼，以便在不同的表單之間共用資源。

因為在共用執行緒上顯示表單比較類似 Windows Form 應用程式的行為，因此您會發現使用 .NET Framework Windows Form 時，如果 .NET Framework 訊息迴圈停止，用戶端應用程式將會關閉。當使用者關閉指定為 ApplicationContext 的主要表單的表單時，便會發生這個行為。 ApplicationContext 是用來開始訊息迴圈的。

在下列程式碼範例中，ApplicationContext 的主要表單會設定為用戶端應用程式所開啟的第一個表單。但是，當使用者關閉此表單執行個體時，便會結束 .NET Framework 訊息迴圈，並且所有其他的 Windows Form 都會關閉。

Imports System.Windows.Forms
Imports System.Runtime.InteropServices

<ComClass(COMForm.ClassId, COMForm.InterfaceId, COMForm.EventsId)> _
Public Class COMForm

#Region "COM GUIDs"
    ' These  GUIDs provide the COM identity for this class 
    ' and its COM interfaces. If you change them, existing 
    ' clients will no longer be able to access the class.
    Public Const ClassId As String = "9322c6dd-2738-428b-ba89-414ce2ea1941"
    Public Const InterfaceId As String = "210f5b8e-296a-4e26-bd7b-cd2cffa43389"
    Public Const EventsId As String = "f25c0ebb-2a2e-42b5-bf20-4bb84989a7da"
#End Region

    ' A creatable COM class must have a Public Sub New() 
    ' with no parameters, otherwise, the class will not be 
    ' registered in the COM registry and cannot be created 
    ' via CreateObject.
    Public Sub New()
        MyBase.New()
    End Sub

    Private WithEvents frmManager As FormManager

    Public Sub ShowForm1()
        ' Call the StartForm method by using a new instance
        ' of the Form1 class.
        StartForm(New Form1)
    End Sub

    Private Sub StartForm(ByVal frm As Form)

        ' This procedure is used to show all forms
        ' that the client application requests. When the first form
        ' is displayed, this code will create a new message
        ' loop that runs on a new thread. The new form will
        ' be treated as the main form.

        ' Later forms will be shown on the same message loop.
        If IsNothing(frmManager) Then
            frmManager = New FormManager(frm)
        Else
            frmManager.ShowForm(frm)
        End If
    End Sub

    Private Sub frmManager_MessageLoopExit() Handles frmManager.MessageLoopExit
        'Release the reference to the frmManager object.
        frmManager = Nothing
    End Sub

End Class

Imports System.Runtime.InteropServices
Imports System.Threading
Imports System.Windows.Forms

<ComVisible(False)> _
Friend Class FormManager
    ' This class is used so that you can generically pass any
    ' form that you want to the delegate.

    Private WithEvents appContext As ApplicationContext
    Private Delegate Sub FormShowDelegate(ByVal form As Form)
    Event MessageLoopExit()

    Public Sub New(ByVal MainForm As Form)
        Dim t As Thread
        If IsNothing(appContext) Then
            appContext = New ApplicationContext(MainForm)
            t = New Thread(AddressOf StartMessageLoop)
            t.IsBackground = True
            t.SetApartmentState(ApartmentState.STA)
            t.Start()
        End If
    End Sub

    Private Sub StartMessageLoop()
        ' Call the Application.Run method to run the form on its own message loop.
        Application.Run(appContext)
    End Sub

    Public Sub ShowForm(ByVal form As Form)

        Dim formShow As FormShowDelegate

        ' Start the main form first. Otherwise, focus will stay on the 
        ' calling form.
        appContext.MainForm.Activate()

        ' Create a new instance of the FormShowDelegate method, and
        ' then invoke the delegate off the MainForm object.
        formShow = New FormShowDelegate(AddressOf ShowFormOnMainForm_MessageLoop)
        appContext.MainForm.Invoke(formShow, New Object() {form})
    End Sub

    Private Sub ShowFormOnMainForm_MessageLoop(ByVal form As Form)
        form.Show()
    End Sub

    Private Sub ac_ThreadExit(ByVal sender As Object, ByVal e As System.EventArgs) Handles appContext.ThreadExit
        appContext.MainForm.Dispose()
        appContext.MainForm = Nothing
        appContext.Dispose()
        appContext = Nothing
        RaiseEvent MessageLoopExit()
    End Sub
End Class

Imports System.Windows.Forms

Public Class Form1
    Inherits System.Windows.Forms.Form

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        MessageBox.Show("Clicked button")
    End Sub

    'Form overrides dispose to clean up the component list.
    <System.Diagnostics.DebuggerNonUserCode()> _
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing AndAlso components IsNot Nothing Then
            components.Dispose()
        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.
    <System.Diagnostics.DebuggerStepThrough()> _
    Private Sub InitializeComponent()
        Me.TextBox1 = New System.Windows.Forms.TextBox
        Me.TextBox2 = New System.Windows.Forms.TextBox
        Me.TextBox3 = New System.Windows.Forms.TextBox
        Me.Button1 = New System.Windows.Forms.Button
        Me.SuspendLayout()
        '
        'TextBox1
        '
        Me.TextBox1.Location = New System.Drawing.Point(12, 12)
        Me.TextBox1.Name = "TextBox1"
        Me.TextBox1.Size = New System.Drawing.Size(100, 20)
        Me.TextBox1.TabIndex = 0
        '
        'TextBox2
        '
        Me.TextBox2.Location = New System.Drawing.Point(12, 38)
        Me.TextBox2.Name = "TextBox2"
        Me.TextBox2.Size = New System.Drawing.Size(100, 20)
        Me.TextBox2.TabIndex = 1
        '
        'TextBox3
        '
        Me.TextBox3.Location = New System.Drawing.Point(12, 64)
        Me.TextBox3.Name = "TextBox3"
        Me.TextBox3.Size = New System.Drawing.Size(100, 20)
        Me.TextBox3.TabIndex = 2
        '
        'Button1
        '
        Me.Button1.Location = New System.Drawing.Point(12, 90)
        Me.Button1.Name = "Button1"
        Me.Button1.Size = New System.Drawing.Size(75, 23)
        Me.Button1.TabIndex = 3
        Me.Button1.Text = "Button1"
        Me.Button1.UseVisualStyleBackColor = True
        '
        'Form1
        '
        Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
        Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
        Me.ClientSize = New System.Drawing.Size(130, 138)
        Me.Controls.Add(Me.Button1)
        Me.Controls.Add(Me.TextBox3)
        Me.Controls.Add(Me.TextBox2)
        Me.Controls.Add(Me.TextBox1)
        Me.Name = "Form1"
        Me.Text = "Form1"
        Me.ResumeLayout(False)
        Me.PerformLayout()

    End Sub
    Friend WithEvents TextBox1 As System.Windows.Forms.TextBox
    Friend WithEvents TextBox2 As System.Windows.Forms.TextBox
    Friend WithEvents TextBox3 As System.Windows.Forms.TextBox
    Friend WithEvents Button1 As System.Windows.Forms.Button
End Class

編譯程式碼

將 COMForm、Form1 和 FormManager 型別編譯到稱為 COMWinform.dll 的組件中。使用封裝 COM 的組件中所描述的其中一種方法，註冊 COM Interop 的組件。現在，您可以在 Unmanaged 應用程式中使用組件和其對應的型別程式庫 (.tlb) 檔案。例如，您可以在 Visual Basic 6.0 可執行檔專案中，將型別程式庫當做參考使用。