Raises the VisibleChanged event when the Visible property value of the control's container changes.
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
Protected Overridable Sub OnParentVisibleChanged ( _
e As EventArgs _
)protected virtual void OnParentVisibleChanged(
EventArgs e
)protected:
virtual void OnParentVisibleChanged(
EventArgs^ e
)abstract OnParentVisibleChanged :
e:EventArgs -> unit
override OnParentVisibleChanged :
e:EventArgs -> unit Parameters
- e
- Type: System
. . :: . EventArgs
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 OnParentVisibleChanged method also enables 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 InheritorsWhen overriding OnParentVisibleChanged in a derived class, be sure to call the base class's OnParentVisibleChanged 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
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 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:
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 );
}
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.