Control.OnEnter(EventArgs) 方法

定義

命名空間:

System.Windows.Forms

組件:

System.Windows.Forms.dll

來源:

Control.cs

引發 Enter 事件。

protected public:
 virtual void OnEnter(EventArgs ^ e);

protected internal virtual void OnEnter (EventArgs e);

abstract member OnEnter : EventArgs -> unit
override this.OnEnter : EventArgs -> unit

Protected Friend Overridable Sub OnEnter (e As EventArgs)

參數

e

EventArgs

包含事件資料的 EventArgs。

範例

下列程式碼範例會 Enter 使用 事件，在特定情況下變更 的前景和背景色彩 TextBox 。

private:
   void textBox1_Enter( Object^ /*sender*/, System::EventArgs^ /*e*/ )
   {
      // If the TextBox contains text, change its foreground and background colors.
      if ( textBox1->Text != String::Empty )
      {
         textBox1->ForeColor = Color::Red;
         textBox1->BackColor = Color::Black;

         // Move the selection pointer to the end of the text of the control.
         textBox1->Select(textBox1->Text->Length,0);
      }
   }

   void textBox1_Leave( Object^ /*sender*/, System::EventArgs^ /*e*/ )
   {
      // Reset the colors and selection of the TextBox after focus is lost.
      textBox1->ForeColor = Color::Black;
      textBox1->BackColor = Color::White;
      textBox1->Select(0,0);
   }

private void textBox1_Enter(object sender, System.EventArgs e)
{
    // If the TextBox contains text, change its foreground and background colors.
    if (!string.IsNullOrEmpty(textBox1.Text))
    {
        textBox1.ForeColor = Color.Red;
        textBox1.BackColor = Color.Black;
        // Move the selection pointer to the end of the text of the control.
        textBox1.Select(textBox1.Text.Length, 0);
    }
}

private void textBox1_Leave(object sender, System.EventArgs e)
{
    // Reset the colors and selection of the TextBox after focus is lost.
    textBox1.ForeColor = Color.Black;
    textBox1.BackColor = Color.White;
    textBox1.Select(0,0);
}

    Private Sub textBox1_Enter(sender As Object, e As System.EventArgs) Handles textBox1.Enter
        ' If the TextBox contains text, change its foreground and background colors.
        If textBox1.Text <> [String].Empty Then
            textBox1.ForeColor = Color.Red
            textBox1.BackColor = Color.Black
            ' Move the selection pointer to the end of the text of the control.
            textBox1.Select(textBox1.Text.Length, 0)
        End If
    End Sub
   
   
    Private Sub textBox1_Leave(sender As Object, e As System.EventArgs) Handles textBox1.Leave
        ' Reset the colors and selection of the TextBox after focus is lost.
        textBox1.ForeColor = Color.Black
        textBox1.BackColor = Color.White
        textBox1.Select(0, 0)
    End Sub
End Class

備註

引發事件會透過委派叫用此事件處理常式。 如需詳細資訊，請參閱 處理和引發事件。

OnEnter 方法也允許衍生類別處理事件，而不用附加委派。 這是在衍生類別中處理事件的慣用技巧。

給繼承者的注意事項

當在衍生類別中覆寫 OnEnter(EventArgs) 時，請確定呼叫基底類別的 OnEnter(EventArgs) 方法，使已註冊的委派能接收到事件。

另請參閱

• Enter