Control.OnTextChanged(EventArgs) Control.OnTextChanged(EventArgs) Control.OnTextChanged(EventArgs) Control.OnTextChanged(EventArgs) Method

定義

引發 TextChanged 事件。Raises the TextChanged event.

protected:
 virtual void OnTextChanged(EventArgs ^ e);
protected virtual void OnTextChanged (EventArgs e);
abstract member OnTextChanged : EventArgs -> unit
override this.OnTextChanged : EventArgs -> unit
Protected Overridable Sub OnTextChanged (e As EventArgs)

參數

e
EventArgs EventArgs EventArgs EventArgs

包含事件資料的 EventArgsAn EventArgs that contains the event data.

範例

下列程式碼範例會變更ForeColorTextBox衍生的類別顯示貨幣資料。The following code example changes the ForeColor of a TextBox derived class displaying currency data. 此範例會將文字轉換成十進位數字和變更ForeColorColor.Red如果數字為負數,Color.Black如果數字為正數。The example converts the text to a decimal number and changes the ForeColor to Color.Red if the number is negative and to Color.Black if the number is positive. 此範例中,您需要的類別,衍生自TextBox類別。This example requires that you have a class that derives from the TextBox class.

protected:
   virtual void OnTextChanged( System::EventArgs^ e ) override
   {
      try
      {
         // Convert the text to a Double and determine
         // if it is a negative number.
         if ( Double::Parse( this->Text ) < 0 )
         {
            // If the number is negative, display it in Red.
            this->ForeColor = Color::Red;
         }
         else
         {
            // If the number is not negative, display it in Black.
            this->ForeColor = Color::Black;
         }
      }
      catch ( Exception^ ) 
      {
         // If there is an error, display the
         // text using the system colors.
         this->ForeColor = SystemColors::ControlText;
      }

      TextBox::OnTextChanged( e );
   }
protected override void OnTextChanged(System.EventArgs e)
{
   try
   {
      // Convert the text to a Double and determine
      // if it is a negative number.
      if(double.Parse(this.Text) < 0)
      {
         // If the number is negative, display it in Red.
         this.ForeColor = Color.Red;
      }
      else
      {
         // If the number is not negative, display it in Black.
         this.ForeColor = Color.Black;
      }
   }
   catch
   {
      // If there is an error, display the 
      // text using the system colors.
      this.ForeColor = SystemColors.ControlText;
   }
   
   base.OnTextChanged(e);
}
Protected Overrides Sub OnTextChanged(e As System.EventArgs)
   Try
      ' Convert the text to a Double and determine
      ' if it is a negative number.
      If Double.Parse(Me.Text) < 0 Then
         ' If the number is negative, display it in Red.
         Me.ForeColor = Color.Red
      Else
         ' If the number is not negative, display it in Black.
         Me.ForeColor = Color.Black
      End If
   Catch
      ' If there is an error, display the
      ' text using the system colors.
      Me.ForeColor = SystemColors.ControlText
   End Try

   MyBase.OnTextChanged(e)
End Sub

備註

引發事件會透過委派叫用此事件處理常式。Raising an event invokes the event handler through a delegate. 如需詳細資訊,請參閱 < 處理和引發事件For more information, see Handling and Raising Events.

OnTextChanged方法也可讓衍生的類別,而不需要附加委派處理事件。The OnTextChanged method also enables derived classes to handle the event without attaching a delegate. 這是在衍生類別中處理事件的慣用技巧。This is the preferred technique for handling the event in a derived class.

給繼承者的注意事項

當在衍生類別中覆寫 OnTextChanged(EventArgs) 時,請確定呼叫基底類別的 OnTextChanged(EventArgs) 方法,使已註冊的委派能接收到事件。When overriding OnTextChanged(EventArgs) in a derived class, be sure to call the base class's OnTextChanged(EventArgs) method so that registered delegates receive the event.

適用於

另請參閱