Control.OnKeyDown メソッド

KeyDown イベントを発生させます。

Protected Overridable Sub OnKeyDown( _
   ByVal e As KeyEventArgs _)
[C#]
protected virtual void OnKeyDown(KeyEventArgse);
[C++]
protected: virtual void OnKeyDown(KeyEventArgs* e);
[JScript]
protected function OnKeyDown(
   e : KeyEventArgs);

パラメータ

• e
  イベント データを格納している KeyEventArgs 。

解説

イベントが発生すると、デリゲートを使用してイベント ハンドラが呼び出されます。詳細については、「 イベントの発生 」を参照してください。

OnKeyDown メソッドを使用すると、デリゲートを結び付けずに、派生クラスでイベントを処理することもできます。派生クラスでイベントを処理する場合は、この手法をお勧めします。

継承時の注意: 派生クラスで OnKeyDown をオーバーライドする場合は、登録されているデリゲートがイベントを受け取ることができるように、基本クラスの OnKeyDown メソッドを呼び出してください。

使用例

 
' Boolean flag used to determine when a character other than a number is entered.
Private nonNumberEntered As Boolean = False
   
   
' Handle the KeyDown event to determine the type of character entered into the control.
Private Sub textBox1_KeyDown(sender As Object, e As System.Windows.Forms.KeyEventArgs) _
     Handles textBox1.KeyDown
    ' Initialize the flag to false.
    nonNumberEntered = False
  
    ' Determine whether the keystroke is a number from the top of the keyboard.
    If e.KeyCode < Keys.D0 OrElse e.KeyCode > Keys.D9 Then
        ' Determine whether the keystroke is a number from the keypad.
        If e.KeyCode < Keys.NumPad0 OrElse e.KeyCode > Keys.NumPad9 Then
            ' Determine whether the keystroke is a backspace.
            If e.KeyCode <> Keys.Back Then
                ' A non-numerical keystroke was pressed. 
                ' Set the flag to true and evaluate in KeyPress event.
                nonNumberEntered = True
            End If
        End If
    End If
End Sub 'textBox1_KeyDown
   
   
' This event occurs after the KeyDown event and can be used 
' to prevent characters from entering the control.
Private Sub textBox1_KeyPress(sender As Object, e As System.Windows.Forms.KeyPressEventArgs) _
    Handles textBox1.KeyPress
    ' Check for the flag being set in the KeyDown event.
    If nonNumberEntered = True Then
        ' Stop the character from being entered into the control since it is non-numerical.
        e.Handled = True
    End If
End Sub 'textBox1_KeyPress
End Class 'Form1 

[C#] 
// Boolean flag used to determine when a character other than a number is entered.
private bool nonNumberEntered = false;

// Handle the KeyDown event to determine the type of character entered into the control.
private void textBox1_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e)
{
    // Initialize the flag to false.
    nonNumberEntered = false;

    // Determine whether the keystroke is a number from the top of the keyboard.
    if (e.KeyCode < Keys.D0 || e.KeyCode > Keys.D9)
    {
        // Determine whether the keystroke is a number from the keypad.
        if (e.KeyCode < Keys.NumPad0 || e.KeyCode > Keys.NumPad9)
        {
            // Determine whether the keystroke is a backspace.
            if(e.KeyCode != Keys.Back)
            {
                // A non-numerical keystroke was pressed.
                // Set the flag to true and evaluate in KeyPress event.
                nonNumberEntered = true;
            }
        }
    }
}

// This event occurs after the KeyDown event and can be used to prevent
// characters from entering the control.
private void textBox1_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
{
    // Check for the flag being set in the KeyDown event.
    if (nonNumberEntered == true)
    {
        // Stop the character from being entered into the control since it is non-numerical.
        e.Handled = true;
    }
}


[C++] 
// Boolean flag used to determine when a character other than a number is entered.
private:
bool nonNumberEntered;

// Handle the KeyDown event to determine the type of character entered into the control.
void textBox1_KeyDown(Object* /*sender*/, System::Windows::Forms::KeyEventArgs* e)
{
   // Initialize the flag to false.
   nonNumberEntered = false;

   // Determine whether the keystroke is a number from the top of the keyboard.
   if (e->KeyCode < Keys::D0 || e->KeyCode > Keys::D9)
   {
      // Determine whether the keystroke is a number from the keypad.
      if (e->KeyCode < Keys::NumPad0 || e->KeyCode > Keys::NumPad9)
      {
         // Determine whether the keystroke is a backspace.
         if(e->KeyCode != Keys::Back)
         {
            // A non-numerical keystroke was pressed.
            // Set the flag to true and evaluate in KeyPress event.
            nonNumberEntered = true;
         }
      }
   }
}

// This event occurs after the KeyDown event and can be used to prevent
// characters from entering the control.
void textBox1_KeyPress(Object* /*sender*/, System::Windows::Forms::KeyPressEventArgs* e)
{
   // Check for the flag being set in the KeyDown event.
   if (nonNumberEntered == true)
   {
      // Stop the character from being entered into the control since it is non-numerical.
      e->Handled = true;
   }
}

[JScript] JScript のサンプルはありません。Visual Basic、C#、および C++ のサンプルを表示するには、このページの左上隅にある言語のフィルタ ボタン をクリックします。

必要条件

プラットフォーム: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 ファミリ, .NET Compact Framework - Windows CE .NET

参照

Control クラス | Control メンバ | System.Windows.Forms 名前空間 | KeyDown