--- title: "How to: Detect When Text in a TextBox Has Changed" description: Learn how to use the TextChanged event to run a method whenever the text in a TextBox control changes in a Windows Presentation Foundation application. ms.date: "03/30/2017" dev_langs: - "csharp" - "vb" helpviewer_keywords: - "TextBox control [WPF], detecting text change" - "text change [WPF], detecting" - "detecting text change [WPF]" ms.assetid: 1c39ee14-e37f-49fb-a0d1-a9824ca13584 --- # How to: Detect When Text in a TextBox Has Changed This example shows one way to use the event to execute a method whenever the text in a control has changed. In the code-behind class for the [!INCLUDE[TLA2#tla_xaml](../../../includes/tla2sharptla-xaml-md.md)] that contains the control that you want to monitor for changes, insert a method to call whenever the event fires. This method must have a signature that matches what is expected by the delegate. The event handler is called whenever the contents of the control are changed, either by a user or programmatically. > [!NOTE] > This event fires when the control is created and initially populated with text. ## Example In the [!INCLUDE[TLA#tla_xaml](../../../includes/tlasharptla-xaml-md.md)] that defines your control, specify the attribute with a value that matches the event handler method name. [!code-xaml[TextBox_MiscCode#_TextChangedXAML](~/samples/snippets/csharp/VS_Snippets_Wpf/TextBox_MiscCode/CSharp/Window1.xaml#_textchangedxaml)] ## Example In the code-behind class for the [!INCLUDE[TLA2#tla_xaml](../../../includes/tla2sharptla-xaml-md.md)] that contains the control that you want to monitor for changes, insert a method to call whenever the event fires. This method must have a signature that matches what is expected by the delegate. [!code-csharp[TextBox_MiscCode#_TextChangedEventHandler](~/samples/snippets/csharp/VS_Snippets_Wpf/TextBox_MiscCode/CSharp/Window1.xaml.cs#_textchangedeventhandler)] [!code-vb[TextBox_MiscCode#_TextChangedEventHandler](~/samples/snippets/visualbasic/VS_Snippets_Wpf/TextBox_MiscCode/VisualBasic/Window1.xaml.vb#_textchangedeventhandler)] The event handler is called whenever the contents of the control are changed, either by a user or programmatically. > [!NOTE] > This event fires when the control is created and initially populated with text. Comments ## See also - - [TextBox Overview](textbox-overview.md) - [RichTextBox Overview](richtextbox-overview.md)