Control.OnTextChanged Method (EventArgs)

 

Raises the TextChanged event.

Namespace:   System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

protected virtual void OnTextChanged(
	EventArgs e
)

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 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);
}

.NET Framework
Available since 1.1
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