有的時候我們希望在視窗中能夠捕獲整個視窗的按鍵事件。

可是如果視窗中已經添加了可啟用的控制元件的話，

由於事件被控制元件擷取，因此視窗無法獲得鍵盤事件。

該怎麼辦呢？

其實只要把視窗屬性 KeyPreview設定為true,

就可以讓視窗提前處理鍵盤事件了。

這個屬性同樣適用於VB，VC的開發。

以下是MSDN上的例子。

using System.Windows.Forms; using System.Security.Permissions; public class Form1: System.Windows.Forms.Form // Declare the controls contained on the form. { private MyMnemonicButton button1; internal System.Windows.Forms.ListBox ListBox1; public Form1() : base() { // Set KeyPreview object to true to allow the form to process // the key before the control with focus processes it. this.KeyPreview = true; // Add a MyMnemonicButton. button1 = new MyMnemonicButton(); button1.Text = "&Click"; button1.Location = new System.Drawing.Point(100, 120); this.Controls.Add(button1); // Initialize a ListBox control and the form itself. this.ListBox1 = new System.Windows.Forms.ListBox(); this.SuspendLayout(); this.ListBox1.Location = new System.Drawing.Point(8, 8); this.ListBox1.Name = "ListBox1"; this.ListBox1.Size = new System.Drawing.Size(120, 95); this.ListBox1.TabIndex = 0; this.ListBox1.Text = "Press a key"; this.ClientSize = new System.Drawing.Size(292, 266); this.Controls.Add(this.ListBox1); this.Name = "Form1"; this.Text = "Form1"; this.ResumeLayout(false); // Associate the event-handling method with the // KeyDown event. this.KeyDown += new KeyEventHandler(Form1_KeyDown); } // The form will handle all key events before the control with // focus handles them. Show the keys pressed by adding the // KeyCode object to ListBox1. Ensure the processing is passed // to the control with focus by setting the KeyEventArg.Handled // property to false. private void Form1_KeyDown(object sender, KeyEventArgs e) { ListBox1.Items.Add(e.KeyCode); e.Handled = false; } [System.STAThreadAttribute] public static void Main() { Application.Run(new Form1()); } } // This button is a simple extension of the button class that overrides // the ProcessMnemonic method. If the mnemonic is correctly entered, // the message box will appear and the click event will be raised. public class MyMnemonicButton:Button // This method makes sure the control is selectable and the // mneumonic is correct before displaying the message box // and triggering the click event. { [UIPermission( SecurityAction.Demand, Window = UIPermissionWindow.AllWindows)] protected override bool ProcessMnemonic(char inputChar) { if (CanSelect&&IsMnemonic(inputChar, this.Text)) { MessageBox.Show("You've raised the click event " + "using the mnemonic."); this.PerformClick(); return true; } return false; } }