WPF with Automation & AddAutomationEventHandler & TextPattern.TextChangedEvent

If I add an AutomationEventHandler on a textBox and if I use the function GetCurrentPattern(TextPattern.Pattern) as TextPattern, when I enter a character into this textbox, I receive a number of event equal at the number of time I called the function GetCurrentPattern.

Have people has the same problem And how I can have just one event by character

Thanks

This is my code

private void RegisterForEvents()

{

if ((bool)element.GetCurrentPropertyValue(AutomationElement.IsTextPatternAvailableProperty))

{

textHandler = new AutomationEventHandler(OnTextChanged); Automation.AddAutomationEventHandler(TextPattern.TextChangedEvent, element, TreeScope.Element, textHandler);

}

}

private void OnTextChanged(object src, AutomationEventArgs e)

{

AutomationElement eElement = src as AutomationElement;

String text = "";

// Get required control patterns

//

// Once you have an instance of an AutomationElement,

// check if it supports the TextPattern pattern.

TextPattern targetTextPattern = selectionitemElement.GetCurrentPattern(TextPattern.Pattern) as TextPattern;

if (targetTextPattern != null)

{

text = targetTextPattern.DocumentRange.GetText(-1);

}

System.Console.Out.WriteLine("OnTextChanged = "+ text);

}