Selection

RadRichTextBox supports not only selection via the UI, but also programmatic selection. This topic shows how you can use both approaches.

UI Selection

The user is able to select the content inside RadRichTextBox in the same way as in MS Word. This is done by clicking on the desired position and dragging to the desired end of the selection. A multiple ranges selection is also allowed. This one is done by holding the Ctrl key while selecting the different ranges.

You can modify the appearance of the selection in the control through the SelectionFill and SelectionStroke properties of RadRichTextBox.

Customize the appearance of the selection

<telerik:RadRichTextBox Name="radRichTextBox" SelectionStroke="DarkRed"> 
    <telerik:RadRichTextBox.SelectionFill> 
        <SolidColorBrush Color="Red" Opacity="0.5" /> 
    </telerik:RadRichTextBox.SelectionFill> 
</telerik:RadRichTextBox> 

Customize the appearance of the selection

this.radRichTextBox.SelectionFill = new System.Windows.Media.SolidColorBrush(Colors.Red);  
this.radRichTextBox.SelectionFill.Opacity = 0.2; 
this.radRichTextBox.SelectionStroke = System.Windows.Media.Brushes.DarkRed; 

Me.radRichTextBox.SelectionFill = New SolidColorBrush(Colors.Red) 
Ме.radRichTextBox.SelectionFill.Opacity = 0.2 
Ме.radRichTextBox.SelectionStroke = Brushes.DarkRed 

Custom selection colors

Advanced Selection Mode

By default when the user select text the words are selected letter by letter. We have introduced an advanced selection mode that allow you to select whole word automatically. The automatic words selection begins after the selection leaves the first word. This mode can be enabled by the IsAdvancedSelectionEnabled property.

Programmatic Selection

The developer is allowed to manipulate the selection programmatically. This can be used in a lot of scenarios involving editing of the document, or for example, when implementing Search functionality in your RadRichTextBox and you want to select the found string.

The programmatic selection is represented via the DocumentSelection class. The instance of the class gets associated with the RadDocument of RadRichTextBox and allows you to specify selection start and end positions, selection ranges and other. You can manage the selection by either using the Selection property of RadDocument or by creating an instance of the DocumentSelection class.

To learn more about the DocumentPosition read the Positioning topic.

Members of DocumentSelection

Properties:

• Ranges—Holds a collection of all SelectionRange instances in the selection.
• IsEmpty—Holds a value determining whether the selection is empty or not.

Methods for manipulating the selection:

• SelectAll—Selects all the content of the document.
• SetSelectionStart—Empties the selection and begins a new SelectionRange starting at the specified position. This method starts the creation of a range, which should be finished with the AddSelectionEnd method.
• AddSelectionStart—Begins a new SelectionRange starting at the specified position. This method starts the creation of a range, which should be finished with the AddSelectionEnd method.
• AddSelectionEnd—Finishes the started SelectionRange by setting its end.
• SelectAnnotationRange—Selects annotation range including the AnnotationRangeStart and AnnotationRangeEnd elements.
• SelectTableRow—Creates a new selection containing the specific table row.
• SelectTableColumn—Creates a new selection containing all the cells in a table column. There are two overloads that allow you to pass a cell from the column or the table and the grid column index, which should be selected.
• AddDocumentElementToSelection—Adds a specified document element to the existing selection.
• AddTableCellToSelection—Adds a table cell to the existing selection.
• AddParagraphToSelection—Adds a paragraph to the existing selection.

Obtaining information and elements from the selection:

• CopySelectedDocumentElements—Copies all selected document elements to a DocumentFragment instance.
• GetSelectedText—Gets the text from the selection. Offers an overload allowing you to specify whether the result should include the bullet or numbering characters in case a paragraph is in a list.
• GetSelectedParagraphs—Gets the paragraphs included in the selection.
• GetSelectedBoxes<T>—Enumerates through all inline layout boxes of type T included in the selected ranges.
• GetFullSelectionGeometry—Gets a System.Windows.Media.Geometry instance describing the form of the selection.
• GetVisibleSelectionGeometry—Gets a System.Windows.Media.Geometry instance describing the form of the selection visible in the rectangle passed as a parameter.
• CreateDocumentFromSelection—Creates a new RadDocument instance containing the selected elements.
• ContainsAnnotationMarkersOfType<T>—Determines whether the selection contains annotation markers of type T.
• GetAnnotationMarkersOfType<T>—Gets all annotation markers of type T in the selection.
• GetSelectedSingleInline—Gets the selected Inline if it is the only inline selected, otherwise returns null. This method is suitable to check if only an ImageInline is selected, for example.
• ToString—Gets the text from the selected document elements.

Clearing the selection method:

• Clear—Empties the selection.

Events:

• SelectionChanging—Occurs before the selection is changed.
• SelectionChanged—Occurs after the selection is changed. Such an event is exposed by the RadRichTextBox class as well.

Select current word

DocumentPosition startPosition = new DocumentPosition(this.radRichTextBox.Document.CaretPosition); 
DocumentPosition endPosition = new DocumentPosition(startPosition); 
startPosition.MoveToCurrentWordStart(); 
endPosition.MoveToCurrentWordEnd(); 
this.radRichTextBox.Document.Selection.SetSelectionStart(startPosition); 
this.radRichTextBox.Document.Selection.AddSelectionEnd(endPosition); 

Dim startPosition As New DocumentPosition(Me.radRichTextBox.Document.CaretPosition) 
Dim endPosition As New DocumentPosition(startPosition) 
startPosition.MoveToCurrentWordStart() 
endPosition.MoveToCurrentWordEnd() 
Me.radRichTextBox.Document.Selection.SetSelectionStart(startPosition) 
Me.radRichTextBox.Document.Selection.AddSelectionEnd(endPosition) 

The next snippet demonstrates how you can check the content that is selected and select and delete the current paragraph if the text in the selection contains the word "Test".

Select current paragraph and delete it

string selectedText = this.radRichTextBox.Document.Selection.GetSelectedText(); 
 
if (selectedText.Contains("Test")) 
{ 
    this.radRichTextBox.Document.Selection.Clear(); 
    Paragraph currentParagraph = this.radRichTextBox.Document.CaretPosition.GetCurrentParagraph(); 
 
    this.radRichTextBox.Document.Selection.AddDocumentElementToSelection(currentParagraph); 
    this.radRichTextBox.Delete(true); 
} 

Dim selectedText As String = Me.radRichTextBox.Document.Selection.GetSelectedText() 
 
If (selectedText.Contains("Test")) Then 
 
    Me.radRichTextBox.Document.Selection.Clear() 
    Dim currentParagraph As Paragraph = Me.radRichTextBox.Document.CaretPosition.GetCurrentParagraph() 
 
    Me.radRichTextBox.Document.Selection.AddDocumentElementToSelection(currentParagraph) 
    Me.radRichTextBox.Delete(True) 
End If 

What is Selection Range?

The selection in RadRichTextBox consists of selection ranges. These ranges are represented by the SelectionRange class which exposes the following members:

• StartPosition—The position determining the start of the selection range.
• EndPosition—The position determining the end of the selection range.
• ContainsPosition—Method that determines whether the range contains a specified DocumentPosition.
• IsEmpty—Determines whether the range contains any document elements.
• IsReversed—Returns true when the start position is after the end position. This might be achieved as in code as well as when the user starts dragging the mouse from right to left.
• IsValid—A range is considered valid when it has valid start and end positions and is not empty.

• RangeType—When working with ranges, you might need to check what elements are included in a selection range. This could be achieved with the RangeType property of SelectionRange. This property is of type SelectionRangeType and could have one of the following values:

• Composite—Represents selection range with mixed elements.

• Table—SelectionRange, which contains a Table.
• TableRow—The range consists of a TableRow.
• TableCell—TableCell selection range.

Check the type of the elements inside the selection

SelectionRange selectionRange = this.radRichTextBox.Document.Selection.Ranges.First(); 
if (selectionRange.RangeType == SelectionRangeType.Table) 
{ 
    SetTableProperties(); 
} 

Dim selectionRange As SelectionRange = Me.radRichTextBox.Document.Selection.Ranges.First() 
If selectionRange.RangeType = SelectionRangeType.Table Then 
    SetTableProperties() 
End If 

Multi-Range Selection

You can implement multi-range Selection by either calling multiple times the AddSelectionStart and AddSelectionEnd methods of the DocumentSelection class or by working with the Ranges collection.

Here is an example of how you can use the first approach.

Select all occurrences of the "RadRichTextBox" word

DocumentPosition position = new DocumentPosition(this.radRichTextBox.Document); 
do 
{ 
    //GetCurrentSpan().Text returns the word at the position 
    string word = position.GetCurrentSpanBox().Text; 
    if (word.Contains("RadRichTextBox")) 
    { 
        DocumentPosition wordEndPosition = new DocumentPosition(position); 
        wordEndPosition.MoveToCurrentWordEnd(); 
        this.radRichTextBox.Document.Selection.AddSelectionStart(position); 
        this.radRichTextBox.Document.Selection.AddSelectionEnd(wordEndPosition); 
 
    } 
}  
while (position.MoveToNextWordStart()); 

Dim position As New DocumentPosition(Me.radRichTextBox.Document) 
Do 
 'GetCurrentSpan().Text returns the word at the position 
 Dim word As String = position.GetCurrentSpanBox().Text 
 If word.Contains("RadRichTextBox") Then 
  Dim wordEndPosition As New DocumentPosition(position) 
  wordEndPosition.MoveToCurrentWordEnd() 
  Me.radRichTextBox.Document.Selection.AddSelectionStart(position) 
 
  Me.radRichTextBox.Document.Selection.AddSelectionEnd(wordEndPosition) 
 End If 
Loop While position.MoveToNextWordStart() 

Multiple selection in RadRichTextBox

Mouse Selection Settings

• MouseSelectionHandler.DoubleClickTime—This static property controls the double click speed of the RichTextBox. The default value is 400ms. It is different from the default value in .NET which is 500ms. This property allows you to set the value that best suits your case. You can set it in your code usually when initializing the RichTextBox control.

• MouseSelectionHandler.MouseDragThreshold—This static property controls the number of pixels that the mouse needs to travel so that the action is considered a drag operation. The default value is 3.

• MouseSelectionHandler.MouseDoubleClickThreshold—This static property controls the number of pixels that are allowed for the mouse to move when double-clicking. The default value of this property is 1.

Customizing Keyboard Shift Selection

The keyboard selection that happens on Shift + arrow keys press can be customized by creating a custom KeyboardSelectionHandler. The handler is assigned to the KeyboardSelectionHandler property of the ActiveEditorPresenter of RadRichTextBox.

The selection handler allows you to override several methods invoked on selection when using the Shift key.

• UpdateSelection—Allows you to implement custom logic to update the selection of the document manually.
• ExpandDownLeft—The method is invoked on Shift + arrow keys selection when the cursor is inside a table and the right end of the cell content is reached.
• ExpandTopRight—The method is invoked on Shift + arrow keys selection when the cursor is inside a table and the left end of the cell content is reached.

Creating custom KeyboardSelectionHandler

public class CustomSelectionHandler : KeyboardSelectionHandler 
{ 
    public CustomSelectionHandler(RadDocument document) : base(document) 
    { 
    } 
 
    public override DocumentPosition ExpandDownLeft(DocumentPosition currentPosition) 
    { 
        currentPosition.MoveToNext(); 
        return currentPosition; 
    } 
 
    public override DocumentPosition ExpandTopRight(DocumentPosition currentPosition) 
    { 
        currentPosition.MoveToPrevious(); 
        return currentPosition; 
    } 
 
    public override void UpdateSelection(MoveCaretDirections direction = MoveCaretDirections.Unknown) 
    { 
        base.UpdateSelection(direction); 
    } 
} 

Assigning the custom KeyboardSelectionHandler

private void RadRichTextBox_Loaded(object sender, RoutedEventArgs e) 
{ 
    var documentPresenter = (DocumentPresenterBase)this.radRichTextBox.ActiveEditorPresenter; 
    documentPresenter.KeyboardSelectionHandler = new CustomSelectionHandler(this.radRichTextBox.Document); 
} 

See Also

• Positioning
• History
• Clipboard Support