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在 Windows 窗体中使用控件的概述

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本主题介绍 Windows 窗体应用程序的基本元素，并提供一个简单的示例，该示例使用 Windows 窗体应用程序中的控件和处理事件。

简单的 Windows 窗体应用程序

Windows 窗体应用程序至少包含以下元素：

  • 派生自 System.Windows.Forms.Form 的一个或多个类。

  • Main 方法调用 Visual Basic 中的 static（shared）Run 方法，并将 Form 实例传递给该方法。 Run 方法将来自操作系统的消息处理到应用程序。

下面的代码示例演示 Windows 窗体应用程序的基本元素。

Option Explicit  
Option Strict  
  
Imports System  
Imports System.Windows.Forms  
  
Public Class MyForm  
   Inherits Form  
  
   Public Sub New()  
      Me.Text = "Hello World"  
   End Sub 'New  
  
   <STAThread()> _  
   Public Shared Sub Main()  
      Dim aform As New MyForm()  
      ' The Application.Run method processes messages from the operating system
      ' to your application. If you comment out the next line of code,
      ' your application will compile and execute, but because it is not in the  
      ' message loop, it will exit after an instance of the form is created.  
      Application.Run(aform)  
   End Sub  
End Class  

using System;  
using System.Windows.Forms;  
  
public class MyForm : Form {  
  
   public MyForm() {  
      this.Text = "Hello World";  
   }  
   [STAThread]  
   public static void Main(string[] args) {  
     MyForm aform = new MyForm();  
// The Application.Run method processes messages from the operating system
// to your application. If you comment out the next line of code,
// your application will compile and execute, but because it is not in the // message loop, it will exit after an instance of the form is created.  
      Application.Run(aform);  
   }  
}

在 Windows 窗体应用程序中使用控件

下面的代码示例演示了一个简单的应用程序，该应用程序说明了 Windows 窗体应用程序如何使用控件和处理事件。 该示例由窗体上的三个按钮组成;单击时，每个按钮都会更改背景色。

Option Explicit  
Option Strict  
  
Imports System  
Imports System.ComponentModel  
Imports System.Windows.Forms  
Imports System.Resources  
Imports System.Drawing  
  
Public Class MyForm  
   Inherits Form  
   Private red As Button  
   Private blue As Button  
   Private green As Button  
  
   Public Sub New()  
      InitializeComponent()  
   End Sub  
  
   Protected Overloads Overrides Sub Dispose(disposing as Boolean)  
      MyBase.Dispose(disposing)  
   End Sub  
  
   ' InitializeComponent is a helper method for the constructor.
   ' It is included for consistency with code that is
   ' auto-generated by the Windows Forms designer in Visual Studio.
   Private Sub InitializeComponent()  
  
      ' Creates three buttons, sets their properties, and attaches  
      ' an event handler to each button.  
      red = New Button()  
      red.Text = "Red"  
      red.Location = New Point(100, 50)  
      red.Size = New Size(50, 50)  
      AddHandler red.Click, AddressOf button_Click  
      Controls.Add(red)  
  
      blue = New Button()  
      blue.Text = "Blue"  
      blue.Location = New Point(100, 100)  
      blue.Size = New Size(50, 50)  
      AddHandler blue.Click, AddressOf button_Click  
      Controls.Add(blue)  
  
      green = New Button()  
      green.Text = "Green"  
      green.Location = New Point(100, 150)  
      green.Size = New Size(50, 50)  
      AddHandler green.Click, AddressOf button_Click  
      Controls.Add(green)  
   End Sub  
  
   ' Event handler.  
   Private Sub button_Click(sender As Object, e As EventArgs)  
      If sender Is red Then  
         Me.BackColor = Color.Red  
      Else  
         If sender Is blue Then  
            Me.BackColor = Color.Blue  
         Else  
            Me.BackColor = Color.Green  
         End If  
      End If
   End Sub  
  
   ' The STAThreadAttribute informs the common language runtime that  
   ' Windows Forms uses the single-threaded apartment model.  
   <STAThread()> _  
   Public Shared Sub Main()  
      Application.Run(New MyForm())  
   End Sub  
End Class  

using System;  
using System.ComponentModel;  
using System.Windows.Forms;  
using System.Resources;  
using System.Drawing;  
  
public class MyForm : Form {  
   private Button red;  
   private Button blue;  
   private Button green;  
  
   public MyForm() : base() {
      InitializeComponent();
   }  
  
   protected override void Dispose(bool disposing) {  
      base.Dispose(disposing);  
   }  
  
// InitializeComponent is a helper method for the constructor.
// It is included for consistency with code that is
// auto-generated by the Windows Forms designer in Visual Studio.
   private void InitializeComponent() {  
  
// A delegate for the click event of a button. The argument to
// the constructor contains a reference to the method that performs the
// event handling logic.  
      EventHandler handler = new EventHandler(button_Click);  
  
// Creates three buttons, sets their properties, and attaches  
// an event handler to each button.  
  
      red = new Button();  
      red.Text = "Red";  
      red.Location = new Point(100, 50);  
      red.Size = new Size(50, 50);  
      red.Click +=handler;  
      Controls.Add(red);  
  
      blue = new Button();  
      blue.Text = "Blue";  
      blue.Location = new Point(100, 100);  
      blue.Size = new Size(50, 50);  
      blue.Click += handler;  
      Controls.Add(blue);  
  
      green = new Button();  
      green.Text = "Green";  
      green.Location = new Point(100, 150);  
      green.Size = new Size(50, 50);  
      green.Click += handler;  
      Controls.Add(green);
      }  
  
   // Event handler.  
   private void button_Click(object sender, EventArgs e) {  
            if (sender == red) this.BackColor = Color.Red ;  
                  else if (sender == blue) this.BackColor = Color.Blue;  
                  else this.BackColor = Color.Green;  
        }  
   // The STAThreadAttribute informs the common language runtime that  
   // Windows Forms uses the single-threaded apartment model.  
  [STAThread]  
   public static void Main(string[] args) {  
   Application.Run(new MyForm());  
   }  
  
}

另请参阅