TextPointer.GetOffsetToPosition(TextPointer) Method

Reference

Definition

Namespace:: System.Windows.Documents

Assembly:: PresentationFramework.dll

Important

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Returns the count of symbols between the current TextPointer and a second specified TextPointer.

public:
 int GetOffsetToPosition(System::Windows::Documents::TextPointer ^ position);

public int GetOffsetToPosition(System.Windows.Documents.TextPointer position);

member this.GetOffsetToPosition : System.Windows.Documents.TextPointer -> int

Public Function GetOffsetToPosition (position As TextPointer) As Integer

Parameters

position: TextPointer

A TextPointer that specifies a position to find the distance (in symbols) to.

Returns

Int32

The relative number of symbols between the current TextPointer and position. A negative value indicates that the current TextPointer follows the position specified by position, 0 indicates that the positions are equal, and a positive value indicates that the current TextPointer precedes the position specified by position.

Exceptions

ArgumentException

position specifies a position outside of the text container associated with the current position.

Examples

The following example demonstrates a use for this method. The example uses the GetOffsetToPosition method to find the offsets for two TextPointer instances, and then uses this information to save and restore the selection in a RichTextBox. The example assumes that the contents of the RichTextBox have not changed between a selection save and a selection restore.

struct SelectionOffsets { internal int Start; internal int End; }
 
SelectionOffsets GetSelectionOffsetsRTB(RichTextBox richTextBox)
{
    SelectionOffsets selectionOffsets;
 
    TextPointer contentStart = richTextBox.Document.ContentStart;

    // Find the offset for the starting and ending TextPointers.
    selectionOffsets.Start = contentStart.GetOffsetToPosition(richTextBox.Selection.Start);
    selectionOffsets.End = contentStart.GetOffsetToPosition(richTextBox.Selection.End);

    return selectionOffsets;
}

void RestoreSelectionOffsetsRTB(RichTextBox richTextBox, SelectionOffsets selectionOffsets)
{
    TextPointer contentStart = richTextBox.Document.ContentStart;
 
    // Use previously determined offsets to create corresponding TextPointers,
    // and use these to restore the selection.
    richTextBox.Selection.Select(
       contentStart.GetPositionAtOffset(selectionOffsets.Start),
       contentStart.GetPositionAtOffset(selectionOffsets.End)
    );
}

Private Structure SelectionOffsets
    Friend Start As Integer
    Friend [End] As Integer
End Structure

Private Function GetSelectionOffsetsRTB(ByVal richTextBox As RichTextBox) As SelectionOffsets
    Dim selectionOffsets As SelectionOffsets

    Dim contentStart As TextPointer = richTextBox.Document.ContentStart

    ' Find the offset for the starting and ending TextPointers.
    selectionOffsets.Start = contentStart.GetOffsetToPosition(richTextBox.Selection.Start)
    selectionOffsets.End = contentStart.GetOffsetToPosition(richTextBox.Selection.End)

    Return selectionOffsets
End Function

Private Sub RestoreSelectionOffsetsRTB(ByVal richTextBox As RichTextBox, ByVal selectionOffsets As SelectionOffsets)
    Dim contentStart As TextPointer = richTextBox.Document.ContentStart

    ' Use previously determined offsets to create corresponding TextPointers,
    ' and use these to restore the selection.
    richTextBox.Selection.Select(contentStart.GetPositionAtOffset(selectionOffsets.Start), contentStart.GetPositionAtOffset(selectionOffsets.End))
End Sub

Remarks

Any of the following is considered to be a symbol:

An opening or closing tag for a TextElement element.
A UIElement element contained in an InlineUIContainer or BlockUIContainer. Note that such a UIElement is always counted as exactly one symbol; any additional content or elements contained by the UIElement are not counted as symbols.
A 16-bit Unicode character inside of a text Run element.

Applies to

Product	Versions
.NET Framework	3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
Windows Desktop	3.0, 3.1, 5, 6, 7, 8, 9, 10

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