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Andy (Steve) De George
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51 lines
3.0 KiB
Markdown
51 lines
3.0 KiB
Markdown
---
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title: "How to: Detect When Text in a TextBox Has Changed"
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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.
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ms.date: "03/30/2017"
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ms.custom: devdivchpfy22
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dev_langs:
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- "csharp"
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- "vb"
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helpviewer_keywords:
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- "TextBox control [WPF], detecting text change"
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- "text change [WPF], detecting"
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- "detecting text change [WPF]"
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ms.assetid: 1c39ee14-e37f-49fb-a0d1-a9824ca13584
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---
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# How to: Detect When Text in a TextBox Has Changed
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This example shows one way to use the <xref:System.Windows.Controls.Primitives.TextBoxBase.TextChanged> event to execute a method whenever the text in a <xref:System.Windows.Controls.TextBox> control has changed.
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In the code-behind class for the XAML that contains the <xref:System.Windows.Controls.TextBox> control that you want to monitor for changes, insert a method to call whenever the <xref:System.Windows.Controls.Primitives.TextBoxBase.TextChanged> event fires. This method must have a signature that matches what is expected by the <xref:System.Windows.Controls.TextChangedEventHandler> delegate.
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The event handler is called whenever the contents of the <xref:System.Windows.Controls.TextBox> control are changed, either by a user or programmatically.
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> [!NOTE]
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> This event fires when the <xref:System.Windows.Controls.TextBox> control is created and initially populated with text.
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## Define TextBox control
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In the Extensible Application Markup Language (XAML) that defines your <xref:System.Windows.Controls.TextBox> control, specify the <xref:System.Windows.Controls.Primitives.TextBoxBase.TextChanged> attribute with a value that matches the event handler method name.
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[!code-xaml[TextBox_MiscCode#_TextChangedXAML](~/samples/snippets/csharp/VS_Snippets_Wpf/TextBox_MiscCode/CSharp/Window1.xaml#_textchangedxaml)]
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## Monitor the TextBox control changes
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In the code-behind class for the XAML that contains the <xref:System.Windows.Controls.TextBox> control that you want to monitor for changes, insert a method to call whenever the <xref:System.Windows.Controls.Primitives.TextBoxBase.TextChanged> event fires. This method must have a signature that matches what is expected by the <xref:System.Windows.Controls.TextChangedEventHandler> delegate.
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[!code-csharp[TextBox_MiscCode#_TextChangedEventHandler](~/samples/snippets/csharp/VS_Snippets_Wpf/TextBox_MiscCode/CSharp/Window1.xaml.cs#_textchangedeventhandler)]
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[!code-vb[TextBox_MiscCode#_TextChangedEventHandler](~/samples/snippets/visualbasic/VS_Snippets_Wpf/TextBox_MiscCode/VisualBasic/Window1.xaml.vb#_textchangedeventhandler)]
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The event handler is called whenever the contents of the <xref:System.Windows.Controls.TextBox> control are changed, either by a user or programmatically.
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> [!NOTE]
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> This event fires when the <xref:System.Windows.Controls.TextBox> control is created and initially populated with text.
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Comments
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## See also
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- <xref:System.Windows.Controls.TextChangedEventArgs>
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- [TextBox Overview](textbox-overview.md)
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- [RichTextBox Overview](richtextbox-overview.md)
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