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Text Selection

Updated on Mar 26, 2026

The PdfViewer supports text selection both from the UI and programmatically.

WinUI RadPdfViewer

Selecting Text with the UI

To enable text selection from the UI, set the Mode property of RadPdfViewer to TextSelection. For more information refer to the article on the PdfViewer interaction modes.

TextSelection is part of the RadPdfProcessing library which is used for the document model of the PdfViewer.

Set the mode of the PdfViewer

this.pdfViewer.Mode = FixedDocumentViewerMode.TextSelection;

The programmatic selection is part of the RadFixedDocument API (the Document property value of RadPdfViewer). To access it, use its Selection property, which gives access to a TextSelection object that provides a set of properties and methods for selecting text.

The TextSelection class introduces the StartPosition and EndPosition properties that can be used to access the selection range. For more information, refer to the article on text positioning.

Access the current selection positions

TextPosition selectionStart = this.pdfViewer.Document.Selection.StartPosition;
TextPosition selectionEnd = this.pdfViewer.Document.Selection.EndPosition;

To set the selection, use one of the TextSelection methods:

When setting the selection programmatically, the UI will display the selection visual even if the mode of PdfViewer is not set to TextSelection.

SetSelectionStart
SetSelectionEnd

Set the selection by using the SetSelectionStart and Set SelectionEnd methods

	RadFixedPage page = this.pdfViewer.Document.Pages[0];
	TextPosition start = new TextPosition(page, 100);            
	TextPosition end = new TextPosition(page, 200);
	this.pdfViewer.Document.Selection.SetSelectionStart(start);
	this.pdfViewer.Document.Selection.SetSelectionEnd(end);

SetSelection

Set the selection by using the SetSelection method

RadFixedPage page = this.pdfViewer.Document.Pages[0];
TextPosition start = new TextPosition(page, 100);            
TextPosition end = new TextPosition(page, 200);
this.pdfViewer.Document.Selection.SetSelection(start, end);

SelectAll

Select all the text

this.pdfViewer.Document.Selection.SelectAll();

Clear

Clear the text selection

this.pdfViewer.Document.Selection.Clear();

To get the selected text, use the GetSelectedText method of TextSelection.

Getg the selected text

string text = this.pdfViewer.Document.Selection.GetSelectedText();

Events

TextSelection provides the SelectionChanging and SelectionChanged events that can be used to listen for changes in the position.

void SubscribeToEvents()
{
	this.pdfViewer.Document.Selection.SelectionChanging += Selection_SelectionChanging;
	this.pdfViewer.Document.Selection.SelectionChanged += Selection_SelectionChanged;
}

private void Selection_SelectionChanging(object sender, EventArgs e)
{		
}

private void Selection_SelectionChanged(object sender, EventArgs e)
{
}