Export (0) Print
Expand All
Expand Minimize

Control.OnRightToLeftChanged Method

Raises the RightToLeftChanged event.

[Visual Basic]
Protected Overridable Sub OnRightToLeftChanged( _
   ByVal e As EventArgs _
)
[C#]
protected virtual void OnRightToLeftChanged(
 EventArgs e
);
[C++]
protected: virtual void OnRightToLeftChanged(
 EventArgs* e
);
[JScript]
protected function OnRightToLeftChanged(
   e : EventArgs
);

Parameters

e
An EventArgs that contains the event data.

Remarks

Raising an event invokes the event handler through a delegate. For more information, see Raising an Event.

The OnRightToLeftChanged method also allows derived classes to handle the event without attaching a delegate. This is the preferred technique for handling the event in a derived class.

Notes to Inheritors:  When overriding OnRightToLeftChanged in a derived class, be sure to call the base class's OnRightToLeftChanged method so that registered delegates receive the event.

Example

[Visual Basic, C#, C++] The example below is an event-raising method that is executed when the Text property value changes. The Control class has several methods with the name pattern On PropertyName Changed that raise the corresponding PropertyName Changed event when the PropertyName value changes(PropertyName represents the name of the corresponding property).

[Visual Basic, C#, C++] The following example changes the ForeColor of a TextBox derived class displaying currency data. 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. This example assumes you have a class that derives from the TextBox class.

[Visual Basic] 
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

[C#] 
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);
}

[C++] 
protected:
   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 (Exception*) {
         // If there is an error, display the
         // text using the system colors.
         this->ForeColor = SystemColors::ControlText;
      }

      TextBox::OnTextChanged(e);
   }

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

See Also

Control Class | Control Members | System.Windows.Forms Namespace | RightToLeftChanged

Show:
© 2014 Microsoft