Control.Invoke 方法

定義

命名空間:

System.Windows.Forms

組件:

System.Windows.Forms.dll

在擁有控制項基礎視窗控制代碼的執行緒上執行委派。

多載

Invoke(Action)	在擁有控制項基礎視窗控制代碼的執行緒上執行指定的委派。
Invoke(Delegate)	在擁有控制項基礎視窗控制代碼的執行緒上執行指定的委派。
Invoke(Delegate, Object[])	在擁有控制項基礎視窗控制代碼的執行緒上，以指定的引數清單執行指定的委派。
Invoke<T>(Func<T>)	在擁有控制項基礎視窗控制代碼的執行緒上執行指定的委派。

Invoke(Action)

在擁有控制項基礎視窗控制代碼的執行緒上執行指定的委派。

public:
 void Invoke(Action ^ method);

public void Invoke (Action method);

member this.Invoke : Action -> unit

Public Sub Invoke (method As Action)

參數

method

Action

委派，包含要在控制項執行緒內容中呼叫的方法。

Invoke(Delegate)

在擁有控制項基礎視窗控制代碼的執行緒上執行指定的委派。

public:
 System::Object ^ Invoke(Delegate ^ method);

public object Invoke (Delegate method);

member this.Invoke : Delegate -> obj

Public Function Invoke (method As Delegate) As Object

參數

method

Delegate

委派，包含要在控制項執行緒內容中呼叫的方法。

傳回

Object

來自所叫用的委派的傳回值，或者如果委派沒有任何傳回值，則為 null。

範例

下列程式碼範例顯示包含委派的控制項。 委派會封裝將專案新增至清單方塊的方法，而且這個方法會在擁有表單基礎控制碼的執行緒上執行。 當使用者按一下按鈕時， Invoke 執行委派。

/*
The following example demonstrates the 'Invoke(Delegate*)' method of 'Control class.
A 'ListBox' and a 'Button' control are added to a form, containing a delegate
which encapsulates a method that adds items to the listbox. This function is executed
on the thread that owns the underlying handle of the form. When user clicks on button
the above delegate is executed using 'Invoke' method.
*/

#using <System.dll>
#using <System.Drawing.dll>
#using <System.Windows.Forms.dll>

using namespace System;
using namespace System::Drawing;
using namespace System::Windows::Forms;
using namespace System::Threading;

public ref class MyFormControl: public Form
{
public:
   delegate void AddListItem();
   AddListItem^ myDelegate;

private:
   Button^ myButton;
   Thread^ myThread;
   ListBox^ myListBox;

public:
   MyFormControl();
   void AddListItemMethod()
   {
      String^ myItem;
      for ( int i = 1; i < 6; i++ )
      {
         myItem = "MyListItem {0}",i;
         myListBox->Items->Add( myItem );
         myListBox->Update();
         Thread::Sleep( 300 );
      }
   }

private:
   void Button_Click( Object^ /*sender*/, EventArgs^ /*e*/ )
   {
      myThread = gcnew Thread( gcnew ThreadStart( this, &MyFormControl::ThreadFunction ) );
      myThread->Start();
   }

   void ThreadFunction();
};


// The following code assumes a 'ListBox' and a 'Button' control are added to a form,
// containing a delegate which encapsulates a method that adds items to the listbox.
public ref class MyThreadClass
{
private:
   MyFormControl^ myFormControl1;

public:
   MyThreadClass( MyFormControl^ myForm )
   {
      myFormControl1 = myForm;
   }

   void Run()
   {
      // Execute the specified delegate on the thread that owns
      // 'myFormControl1' control's underlying window handle.
      myFormControl1->Invoke( myFormControl1->myDelegate );
   }
};


MyFormControl::MyFormControl()
{
   myButton = gcnew Button;
   myListBox = gcnew ListBox;
   myButton->Location = Point( 72, 160 );
   myButton->Size = System::Drawing::Size( 152, 32 );
   myButton->TabIndex = 1;
   myButton->Text = "Add items in list box";
   myButton->Click += gcnew EventHandler( this, &MyFormControl::Button_Click );
   myListBox->Location = Point( 48, 32 );
   myListBox->Name = "myListBox";
   myListBox->Size = System::Drawing::Size( 200, 95 );
   myListBox->TabIndex = 2;
   ClientSize = System::Drawing::Size( 292, 273 );
   array<Control^>^ temp0 = {myListBox,myButton};
   Controls->AddRange( temp0 );
   Text = " 'Control_Invoke' example";
   myDelegate = gcnew AddListItem( this, &MyFormControl::AddListItemMethod );
}

void MyFormControl::ThreadFunction()
{
   MyThreadClass^ myThreadClassObject = gcnew MyThreadClass( this );
   myThreadClassObject->Run();
}

int main()
{
   MyFormControl^ myForm = gcnew MyFormControl;
   myForm->ShowDialog();
}

/*
The following example demonstrates the 'Invoke(Delegate)' method of 'Control class.
A 'ListBox' and a 'Button' control are added to a form, containing a delegate
which encapsulates a method that adds items to the listbox. This function is executed
on the thread that owns the underlying handle of the form. When user clicks on button
the above delegate is executed using 'Invoke' method.


*/

using System;
using System.Drawing;
using System.Windows.Forms;
using System.Threading;

   public class MyFormControl : Form
   {
      public delegate void AddListItem();
      public AddListItem myDelegate;
      private Button myButton;
      private Thread myThread;
      private ListBox myListBox;
      public MyFormControl()
      {
         myButton = new Button();
         myListBox = new ListBox();
         myButton.Location = new Point(72, 160);
         myButton.Size = new Size(152, 32);
         myButton.TabIndex = 1;
         myButton.Text = "Add items in list box";
         myButton.Click += new EventHandler(Button_Click);
         myListBox.Location = new Point(48, 32);
         myListBox.Name = "myListBox";
         myListBox.Size = new Size(200, 95);
         myListBox.TabIndex = 2;
         ClientSize = new Size(292, 273);
         Controls.AddRange(new Control[] {myListBox,myButton});
         Text = " 'Control_Invoke' example";
         myDelegate = new AddListItem(AddListItemMethod);
      }
      static void Main()
      {
         MyFormControl myForm = new MyFormControl();
         myForm.ShowDialog();
      }
      public void AddListItemMethod()
      {
         String myItem;
         for(int i=1;i<6;i++)
         {
            myItem = "MyListItem" + i.ToString();
            myListBox.Items.Add(myItem);
            myListBox.Update();
            Thread.Sleep(300);
         }
      }
      private void Button_Click(object sender, EventArgs e)
      {
         myThread = new Thread(new ThreadStart(ThreadFunction));
         myThread.Start();
      }
      private void ThreadFunction()
      {
         MyThreadClass myThreadClassObject  = new MyThreadClass(this);
         myThreadClassObject.Run();
      }
   }

// The following code assumes a 'ListBox' and a 'Button' control are added to a form, 
// containing a delegate which encapsulates a method that adds items to the listbox.

   public class MyThreadClass
   {
      MyFormControl myFormControl1;
      public MyThreadClass(MyFormControl myForm)
      {
         myFormControl1 = myForm;
      }

      public void Run()
      {
         // Execute the specified delegate on the thread that owns
         // 'myFormControl1' control's underlying window handle.
         myFormControl1.Invoke(myFormControl1.myDelegate);
      }
   }

' The following example demonstrates the 'Invoke(Delegate)' method of 'Control class.
' A 'ListBox' and a 'Button' control are added to a form, containing a delegate
' which encapsulates a method that adds items to the listbox. This function is executed
' on the thread that owns the underlying handle of the form. When user clicks on button
' the above delegate is executed using 'Invoke' method.

Imports System.Drawing
Imports System.Windows.Forms
Imports System.Threading

Public Class MyFormControl
   Inherits Form

   Delegate Sub AddListItem()
   Public myDelegate As AddListItem
   Private myButton As Button
   Private myThread As Thread
   Private myListBox As ListBox

   Public Sub New()
      myButton = New Button()
      myListBox = New ListBox()
      myButton.Location = New Point(72, 160)
      myButton.Size = New Size(152, 32)
      myButton.TabIndex = 1
      myButton.Text = "Add items in list box"
      AddHandler myButton.Click, AddressOf Button_Click
      myListBox.Location = New Point(48, 32)
      myListBox.Name = "myListBox"
      myListBox.Size = New Size(200, 95)
      myListBox.TabIndex = 2
      ClientSize = New Size(292, 273)
      Controls.AddRange(New Control() {myListBox, myButton})
      Text = " 'Control_Invoke' example"
      myDelegate = New AddListItem(AddressOf AddListItemMethod)
   End Sub

   Shared Sub Main()
      Dim myForm As New MyFormControl()
      myForm.ShowDialog()
   End Sub

   Public Sub AddListItemMethod()
      Dim myItem As String
      Dim i As Integer
      For i = 1 To 5
         myItem = "MyListItem" + i.ToString()
         myListBox.Items.Add(myItem)
         myListBox.Update()
         Thread.Sleep(300)
      Next i
   End Sub

   Private Sub Button_Click(sender As Object, e As EventArgs)
      myThread = New Thread(New ThreadStart(AddressOf ThreadFunction))
      myThread.Start()
   End Sub

   Private Sub ThreadFunction()
      Dim myThreadClassObject As New MyThreadClass(Me)
      myThreadClassObject.Run()
   End Sub
End Class


' The following code assumes a 'ListBox' and a 'Button' control are added to a form, 
' containing a delegate which encapsulates a method that adds items to the listbox.
Public Class MyThreadClass
   Private myFormControl1 As MyFormControl

   Public Sub New(myForm As MyFormControl)
      myFormControl1 = myForm
   End Sub

   Public Sub Run()
      ' Execute the specified delegate on the thread that owns
      ' 'myFormControl1' control's underlying window handle.
      myFormControl1.Invoke(myFormControl1.myDelegate)
   End Sub

End Class

備註

委派類似于 C 或 C++ 語言中的函式指標。 委派會封裝委派物件內方法的參考。 委派物件接著可以傳遞至呼叫參考方法的程式碼，而且在編譯時期叫用的方法可能未知。 不同于 C 或 C++ 中的函式指標，委派是物件導向、型別安全且更安全。

如果目前控制項的基礎視窗控制碼不存在，方法 Invoke 會搜尋控制項的父鏈結，直到它找到具有視窗控制碼的控制項或表單為止。 如果找不到適當的控制碼，方法 Invoke 會擲回例外狀況。 呼叫期間引發的例外狀況會傳播回呼叫端。

注意

除了 屬性之外 InvokeRequired ，控制項上還有四個安全線程的方法： Invoke 、、 BeginInvokeEndInvoke 和 CreateGraphics 如果已經建立控制項的控制碼。 在背景執行緒上建立控制項控制碼之前呼叫 CreateGraphics ，可能會導致不合法的跨執行緒呼叫。 對於所有其他方法呼叫，您應該使用其中一個叫用方法來封送處理控制項執行緒的呼叫。

委派可以是 的 EventHandler 實例，在此情況下，sender 參數將包含此控制項，而事件參數將包含 EventArgs.Empty 。 委派也可以是 的實例，或任何其他接受 void 參數清單的 MethodInvoker 委派。 對 或 MethodInvoker 委派的呼叫 EventHandler 會比呼叫其他類型的委派更快。

注意

如果應該處理訊息的執行緒不再使用中，可能會擲回例外狀況。

另請參閱

• MethodInvoker
• InvokeRequired

Invoke(Delegate, Object[])

在擁有控制項基礎視窗控制代碼的執行緒上，以指定的引數清單執行指定的委派。

public:
 virtual System::Object ^ Invoke(Delegate ^ method, ... cli::array <System::Object ^> ^ args);

public object Invoke (Delegate method, params object?[]? args);

abstract member Invoke : Delegate * obj[] -> obj
override this.Invoke : Delegate * obj[] -> obj

Public Function Invoke (method As Delegate, ParamArray args As Object()) As Object

參數

method

Delegate

方法的委派，採用和 args 參數中包含者相同的數字和類型的參數。

args

Object[]

做為引數傳遞至指定方法的物件陣列。 如果方法沒有引數，這個參數可能是 null。

傳回

Object

Object，包含所叫用的委派的傳回值，如果委派沒有傳回值，則為 null。

實作

Invoke(Delegate, Object[])

範例

下列程式碼範例顯示包含委派的控制項。 委派會封裝方法，以將專案新增至清單方塊，而且這個方法會在擁有表單基礎控制碼的執行緒上執行，並使用指定的引數。 當使用者按一下按鈕時， Invoke 執行委派。

using namespace System;
using namespace System::Drawing;
using namespace System::ComponentModel;
using namespace System::Windows::Forms;
using namespace System::Threading;
ref class MyFormControl: public Form
{
public:
   delegate void AddListItem( String^ myString );
   AddListItem^ myDelegate;

private:
   Button^ myButton;
   Thread^ myThread;
   ListBox^ myListBox;

public:
   MyFormControl();
   void AddListItemMethod( String^ myString );

private:
   void Button_Click( Object^ sender, EventArgs^ e );
   void ThreadFunction();
};

ref class MyThreadClass
{
private:
   MyFormControl^ myFormControl1;

public:
   MyThreadClass( MyFormControl^ myForm )
   {
      myFormControl1 = myForm;
   }

   String^ myString;
   void Run()
   {
      for ( int i = 1; i <= 5; i++ )
      {
         myString = String::Concat( "Step number ", i, " executed" );
         Thread::Sleep( 400 );
         
         // Execute the specified delegate on the thread that owns
         // 'myFormControl1' control's underlying window handle with
         // the specified list of arguments.
         array<Object^>^myStringArray = {myString};
         myFormControl1->Invoke( myFormControl1->myDelegate, myStringArray );

      }
   }

};

MyFormControl::MyFormControl()
{
   myButton = gcnew Button;
   myListBox = gcnew ListBox;
   myButton->Location = Point(72,160);
   myButton->Size = System::Drawing::Size( 152, 32 );
   myButton->TabIndex = 1;
   myButton->Text = "Add items in list box";
   myButton->Click += gcnew EventHandler( this, &MyFormControl::Button_Click );
   myListBox->Location = Point(48,32);
   myListBox->Name = "myListBox";
   myListBox->Size = System::Drawing::Size( 200, 95 );
   myListBox->TabIndex = 2;
   ClientSize = System::Drawing::Size( 292, 273 );
   array<Control^>^formControls = {myListBox,myButton};
   Controls->AddRange( formControls );
   Text = " 'Control_Invoke' example ";
   myDelegate = gcnew AddListItem( this, &MyFormControl::AddListItemMethod );
}

void MyFormControl::AddListItemMethod( String^ myString )
{
   myListBox->Items->Add( myString );
}

void MyFormControl::Button_Click( Object^ /*sender*/, EventArgs^ /*e*/ )
{
   myThread = gcnew Thread( gcnew ThreadStart( this, &MyFormControl::ThreadFunction ) );
   myThread->Start();
}

void MyFormControl::ThreadFunction()
{
   MyThreadClass^ myThreadClassObject = gcnew MyThreadClass( this );
   myThreadClassObject->Run();
}

int main()
{
   MyFormControl^ myForm = gcnew MyFormControl;
   myForm->ShowDialog();
}

using System;
using System.Drawing;
using System.Windows.Forms;
using System.Threading;

   public class MyFormControl : Form
   {
      public delegate void AddListItem(String myString);
      public AddListItem myDelegate;
      private Button myButton;
      private Thread myThread;
      private ListBox myListBox;
      public MyFormControl()
      {
         myButton = new Button();
         myListBox = new ListBox();
         myButton.Location = new Point(72, 160);
         myButton.Size = new Size(152, 32);
         myButton.TabIndex = 1;
         myButton.Text = "Add items in list box";
         myButton.Click += new EventHandler(Button_Click);
         myListBox.Location = new Point(48, 32);
         myListBox.Name = "myListBox";
         myListBox.Size = new Size(200, 95);
         myListBox.TabIndex = 2;
         ClientSize = new Size(292, 273);
         Controls.AddRange(new Control[] {myListBox,myButton});
         Text = " 'Control_Invoke' example ";
         myDelegate = new AddListItem(AddListItemMethod);
      }
      static void Main()
      {
         MyFormControl myForm = new MyFormControl();
         myForm.ShowDialog();
      }
      public void AddListItemMethod(String myString)
      {
            myListBox.Items.Add(myString);
      }
      private void Button_Click(object sender, EventArgs e)
      {
         myThread = new Thread(new ThreadStart(ThreadFunction));
         myThread.Start();
      }
      private void ThreadFunction()
      {
         MyThreadClass myThreadClassObject  = new MyThreadClass(this);
         myThreadClassObject.Run();
      }
   }
   public class MyThreadClass
   {
      MyFormControl myFormControl1;
      public MyThreadClass(MyFormControl myForm)
      {
         myFormControl1 = myForm;
      }
      String myString;

      public void Run()
      {

         for (int i = 1; i <= 5; i++)
         {
            myString = "Step number " + i.ToString() + " executed";
            Thread.Sleep(400);
            // Execute the specified delegate on the thread that owns
            // 'myFormControl1' control's underlying window handle with
            // the specified list of arguments.
            myFormControl1.Invoke(myFormControl1.myDelegate,
                                   new Object[] {myString});
         }
      }
   }

Imports System.Drawing
Imports System.Windows.Forms
Imports System.Threading

Public Class MyFormControl
   Inherits Form

   Delegate Sub AddListItem(myString As String)
   Public myDelegate As AddListItem
   Private myButton As Button
   Private myThread As Thread
   Private myListBox As ListBox

   Public Sub New()
      myButton = New Button()
      myListBox = New ListBox()
      myButton.Location = New Point(72, 160)
      myButton.Size = New Size(152, 32)
      myButton.TabIndex = 1
      myButton.Text = "Add items in list box"
      AddHandler myButton.Click, AddressOf Button_Click
      myListBox.Location = New Point(48, 32)
      myListBox.Name = "myListBox"
      myListBox.Size = New Size(200, 95)
      myListBox.TabIndex = 2
      ClientSize = New Size(292, 273)
      Controls.AddRange(New Control() {myListBox, myButton})
      Text = " 'Control_Invoke' example "
      myDelegate = New AddListItem(AddressOf AddListItemMethod)
   End Sub

   Shared Sub Main()
      Dim myForm As New MyFormControl()
      myForm.ShowDialog()
   End Sub

   Public Sub AddListItemMethod(myString As String)
      myListBox.Items.Add(myString)
   End Sub

   Private Sub Button_Click(sender As Object, e As EventArgs)
      myThread = New Thread(New ThreadStart(AddressOf ThreadFunction))
      myThread.Start()
   End Sub

   Private Sub ThreadFunction()
      Dim myThreadClassObject As New MyThreadClass(Me)
      myThreadClassObject.Run()
   End Sub
End Class

Public Class MyThreadClass
   Private myFormControl1 As MyFormControl

   Public Sub New(myForm As MyFormControl)
      myFormControl1 = myForm
   End Sub
   Private myString As String

   Public Sub Run()

      Dim i As Integer
      For i = 1 To 5
         myString = "Step number " + i.ToString() + " executed"
         Thread.Sleep(400)
         ' Execute the specified delegate on the thread that owns
         ' 'myFormControl1' control's underlying window handle with
         ' the specified list of arguments.
         myFormControl1.Invoke(myFormControl1.myDelegate, New Object() {myString})
      Next i

   End Sub
End Class

備註

委派類似于 C 或 C++ 語言中的函式指標。 委派會封裝委派物件內方法的參考。 委派物件接著可以傳遞至呼叫參考方法的程式碼，而且在編譯時期叫用的方法可能未知。 不同于 C 或 C++ 中的函式指標，委派是物件導向、型別安全且更安全。

如果控制項的控制碼尚不存在，這個方法會搜尋控制項的父鏈結，直到找到具有視窗控制碼的控制項或表單為止。 如果找不到適當的控制碼，這個方法會擲回例外狀況。 呼叫期間引發的例外狀況會傳播回呼叫端。

注意

除了 屬性之外 InvokeRequired ，控制項上還有四個安全線程的方法： Invoke 、、 BeginInvokeEndInvoke 和 CreateGraphics 如果已經建立控制項的控制碼。 在背景執行緒上建立控制項控制碼之前呼叫 CreateGraphics ，可能會導致不合法的跨執行緒呼叫。 對於所有其他方法呼叫，您應該使用其中一個叫用方法來封送處理控制項執行緒的呼叫。

委派可以是 的 EventHandler 實例，在此情況下，sender 參數將包含此控制項，而事件參數將包含 EventArgs.Empty 。 委派也可以是 的實例，或任何其他接受 void 參數清單的 MethodInvoker 委派。 對 或 MethodInvoker 委派的呼叫 EventHandler 會比呼叫其他類型的委派更快。

注意

如果應該處理訊息的執行緒不再使用中，可能會擲回例外狀況。

另請參閱

• MethodInvoker
• InvokeRequired

Invoke<T>(Func<T>)

在擁有控制項基礎視窗控制代碼的執行緒上執行指定的委派。

public:
generic <typename T>
 T Invoke(Func<T> ^ method);

public T Invoke<T> (Func<T> method);

member this.Invoke : Func<'T> -> 'T

Public Function Invoke(Of T) (method As Func(Of T)) As T

類型參數

T

的 method 傳回型別。

參數

method

Func<T>

在控制項的執行緒內容中呼叫的函式。

傳回

T

正在叫用之函式的傳回值。