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32 lines
3.2 KiB
Markdown
32 lines
3.2 KiB
Markdown
---
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title: "How to: Open a File That is Dropped on a RichTextBox Control"
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ms.date: "03/30/2017"
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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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- "drag-and-drop [WPF], RichTextBox"
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- "RichTextBox [WPF], drag-and-drop"
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- "drag-and-drop [WPF], open a dropped file"
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ms.assetid: 6bb8bb54-f576-41db-a9a7-24102ddeb490
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---
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# How to: Open a File That is Dropped on a RichTextBox Control
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In [!INCLUDE[TLA#tla_winclient](../../../includes/tlasharptla-winclient-md.md)], the <xref:System.Windows.Controls.TextBox>, <xref:System.Windows.Controls.RichTextBox>, and <xref:System.Windows.Documents.FlowDocument> controls all have built-in drag-and-drop functionality. The built-in functionality enables drag-and-drop of text within and between the controls. However, it does not enable opening a file by dropping the file on the control. These controls also mark the drag-and-drop events as handled. As a result, by default, you cannot add your own event handlers to provide functionality to open dropped files.
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To add additional handling for drag-and-drop events in these controls, use the <xref:System.Windows.UIElement.AddHandler%28System.Windows.RoutedEvent%2CSystem.Delegate%2CSystem.Boolean%29> method to add your event handlers for the drag-and-drop events. Set the `handledEventsToo` parameter to `true` to have the specified handler be invoked for a routed event that has already been marked as handled by another element along the event route.
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> [!TIP]
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> You can replace the built-in drag-and-drop functionality of <xref:System.Windows.Controls.TextBox>, <xref:System.Windows.Controls.RichTextBox>, and <xref:System.Windows.Documents.FlowDocument> by handling the preview versions of the drag-and-drop events and marking the preview events as handled. However, this will disable the built-in drag-and-drop functionality, and is not recommended.
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## Example
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The following example demonstrates how to add handlers for the <xref:System.Windows.DragDrop.DragOver> and <xref:System.Windows.DragDrop.Drop> events on a <xref:System.Windows.Controls.RichTextBox>. This example uses the <xref:System.Windows.UIElement.AddHandler%28System.Windows.RoutedEvent%2CSystem.Delegate%2CSystem.Boolean%29> method and sets the `handledEventsToo` parameter to `true` so that the events handlers will be invoked even though the <xref:System.Windows.Controls.RichTextBox> marks these events as handled. The code in the event handlers adds functionality to open a text file that is dropped on the <xref:System.Windows.Controls.RichTextBox>.
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To test this example, drag a text file or a rich text format (RTF) file from Windows Explorer to the <xref:System.Windows.Controls.RichTextBox>. The file will be opened in the <xref:System.Windows.Controls.RichTextBox>. If you press the SHIFT key before the dropping the file, the file will be opened as plain text.
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[!code-xaml[DragDropSnippets#RtbXAML](~/samples/snippets/csharp/VS_Snippets_Wpf/dragdropsnippets/cs/mainwindow.xaml#rtbxaml)]
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[!code-csharp[DragDropSnippets#RtbHandlers](~/samples/snippets/csharp/VS_Snippets_Wpf/dragdropsnippets/cs/mainwindow.xaml.cs#rtbhandlers)]
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[!code-vb[DragDropSnippets#RtbHandlers](~/samples/snippets/visualbasic/VS_Snippets_Wpf/dragdropsnippets/vb/mainwindow.xaml.vb#rtbhandlers)]
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