Control.OnTextChanged Method
Raises the TextChanged event.
[Visual Basic] Protected Overridable Sub OnTextChanged( _ ByVal e As EventArgs _ ) [C#] protected virtual void OnTextChanged( EventArgs e ); [C++] protected: virtual void OnTextChanged( EventArgs* e ); [JScript] protected function OnTextChanged( 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 OnTextChanged 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 OnTextChanged in a derived class, be sure to call the base class's OnTextChanged method so that registered delegates receive the event.
Example
[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
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 | TextChanged