Control.KeyDown イベント

.NET Framework クラス ライブラリ リファレンス

Control.KeyDown イベント

コントロールにフォーカスがあるときにキーが押されると発生します。

名前空間: System.Windows.Forms
アセンブリ: System.Windows.Forms (system.windows.forms.dll 内)
構文

Visual Basic (宣言)

Public Event KeyDown As
 KeyEventHandler

Visual Basic (使用法)

Dim instance As Control
Dim handler As KeyEventHandler

AddHandler instance.KeyDown, handler

C#

public event KeyEventHandler KeyDown

C++

public:
event KeyEventHandler^ KeyDown {
    void add (KeyEventHandler^ value);
    void remove (KeyEventHandler^ value);
}

J#

/** @event */
public void add_KeyDown (KeyEventHandler value)

/** @event */
public void remove_KeyDown (KeyEventHandler
 value)

JScript

JScript では、イベントは使用できますが、新規に宣言することはできません。

解説

キー イベントは次の順序で発生します。

1. KeyDown

2. KeyPress

3. KeyUp

キーボード イベントをフォームでだけ処理し、そのイベントを他のコントロールでは受け取らないようにする場合は、フォームの KeyPress イベント処理メソッドの KeyPressEventArgs.Handled プロパティを true に設定します。Tab キー、Enter キー、Esc キー、方向キーなどは、コントロールによって自動処理されます。これらのキーで KeyDown イベントを発生させるには、フォーム上の各コントロールで IsInputKey メソッドをオーバーライドする必要があります。IsInputKey のオーバーライドのコードは、特殊なキーのいずれかが押され、そのキーが true の値を返したかどうかを判断する必要があります。

イベント処理の詳細については、「イベントの利用」を参照してください。

使用例

KeyDown イベントを使用して、コントロールに入力された文字の種類を判断するコード例を次に示します。

Visual Basic

    ' 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;
      }
   }

J#

// Boolean flag used to determine when a character other than a number
 
// is entered.
private boolean 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.get_KeyCode().CompareTo(Keys.D0)) < 0 
        || (e.get_KeyCode().CompareTo(Keys.D9) > 0)) {

        // Determine whether the keystroke is a number from the keypad.
        if ((e.get_KeyCode().CompareTo(Keys.NumPad0) < 0 
            || (e.get_KeyCode().CompareTo(Keys.NumPad9)) > 0)) {

            // Determine whether the keystroke is a backspace.
            if (!(e.get_KeyCode().Equals(Keys.Back))) {
                    // A non-numerical keystroke was pressed.
                    // Set the flag to true and evaluate in KeyPress
 event.
                    nonNumberEntered = true;
            }
        }
    }
} //textBox1_KeyDown

// 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.set_Handled(true);
    }
} //textBox1_KeyPress

プラットフォーム

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

開発プラットフォームの中には、.NET Framework によってサポートされていないバージョンがあります。サポートされているバージョンについては、「システム要件」を参照してください。

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0
.NET Compact Framework
サポート対象 : 2.0、1.0

参照

関連項目
Control クラス
Control メンバ
System.Windows.Forms 名前空間
KeyEventArgs
OnKeyDown
KeyUp
KeyPress