Control.OnParentBindingContextChanged(EventArgs) Control.OnParentBindingContextChanged(EventArgs) Control.OnParentBindingContextChanged(EventArgs) Control.OnParentBindingContextChanged(EventArgs) Method

定義

當控制項容器的 BindingContextChanged 屬性值變更時,會引發 BindingContext 事件。Raises the BindingContextChanged event when the BindingContext property value of the control's container changes.

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

下列程式碼範例是事件引發的方法,是執行時Text屬性值變更。The following code example is an event-raising method that is executed when the Text property value changes. Control類別有數個方法名稱模式On PropertyName Changed會引發對應PropertyName Changed事件時PropertyName值變更 (PropertyName代表對應的屬性名稱)。The Control class has several methods with the name pattern OnPropertyNameChanged that raise the corresponding PropertyNameChanged event when the PropertyName value changes (PropertyName represents the name of the corresponding property).

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.

OnParentBindingContextChanged方法也可讓衍生的類別,而不需要附加委派處理事件。The OnParentBindingContextChanged 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 OnParentBindingContextChanged(EventArgs) 時,請確定呼叫基底類別的 OnParentBindingContextChanged(EventArgs) 方法,使已註冊的委派能接收到事件。When overriding OnParentBindingContextChanged(EventArgs) in a derived class, be sure to call the base class's OnParentBindingContextChanged(EventArgs) method so that registered delegates receive the event.

適用於

另請參閱