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Control.OnContextMenuChanged Method

Raises the ContextMenuChanged event.

Namespace: System.Windows.Forms
Assembly: System.Windows.Forms (in system.windows.forms.dll)

'Declaration
Protected Overridable Sub OnContextMenuChanged ( _
	e As EventArgs _
)
'Usage
Dim e As EventArgs

Me.OnContextMenuChanged(e)
protected void OnContextMenuChanged (
	EventArgs e
)
protected function OnContextMenuChanged (
	e : EventArgs
)

Parameters

e

An EventArgs that contains the event data.

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

The OnContextMenuChanged 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 OnContextMenuChanged in a derived class, be sure to call the base class's OnContextMenuChanged method so that registered delegates receive the event.

The following code example is an event-raising method that is executed when the Text property value changes. 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).

The following code 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 requires that you have a class that derives from the TextBox class.

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

protected void OnTextChanged(System.EventArgs e)
{
    try {
        // Convert the text to a Double and determine
        // if it is a negative number.
        if (System.Double.Parse(this.get_Text()) < 0) {
            // If the number is negative, display it in Red.
            this.set_ForeColor(Color.get_Red());
        }
        else {
            // If the number is not negative, display it in Black.
            this.set_ForeColor(Color.get_Black());
        }
    }
    catch (System.Exception exp) {
        // If there is an error, display the 
        // text using the system colors.
        this.set_ForeColor(SystemColors.get_ControlText());
    }
    super.OnTextChanged(e);
} //OnTextChanged

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0

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