Control.OnTextChanged Method (EventArgs)
Raises the TextChanged event.
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
Raising an event invokes the event handler through a delegate. For more information, see Handling and Raising Events.
The OnTextChanged 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 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.
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 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); }
Available since 1.1