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TextPointer.GetOffsetToPosition Method (TextPointer)

 

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

Namespace:   System.Windows.Documents
Assembly:  PresentationFramework (in PresentationFramework.dll)

public int GetOffsetToPosition(
	TextPointer position
)

Parameters

position
Type: System.Windows.Documents.TextPointer

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

Return Value

Type: System.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.

Exception Condition
ArgumentException

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

Any of the following is considered to be a symbol:

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)
    );
}

.NET Framework
Available since 3.0
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