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Control.OnBindingContextChanged Method

Raises the BindingContextChanged event.

[Visual Basic]
Protected Overridable Sub OnBindingContextChanged( _
   ByVal e As EventArgs _
)
[C#]
protected virtual void OnBindingContextChanged(
 EventArgs e
);
[C++]
protected: virtual void OnBindingContextChanged(
 EventArgs* e
);
[JScript]
protected function OnBindingContextChanged(
   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 OnBindingContextChanged 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 OnBindingContextChanged in a derived class, be sure to call the base class's OnBindingContextChanged 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 event when the property value changes. You can create an event-raising method similar to the following example to raise the appropriate event when the the corresponding property value changes.

[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, .NET Compact Framework

See Also

Control Class | Control Members | System.Windows.Forms Namespace | BindingContextChanged | BindingContext

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