Information
The topic you requested is included in another documentation set. For convenience, it's displayed below. Choose Switch to see the topic in its original location.

TextPointer Class

Represents a position within a FlowDocument or TextBlock.

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

public class TextPointer : ContentPosition

The TextPointer type exposes the following members.

  NameDescription
Public propertyDocumentEndGets a TextPointer at the end of content in the text container associated with the current position.
Public propertyDocumentStartGets a TextPointer at the beginning of content in the text container associated with the current position.
Public propertyHasValidLayoutGets a value that indicates whether the text container associated with the current position has a valid (up-to-date) layout.
Public propertyIsAtInsertionPositionGets a value that indicates whether the current position is an insertion position.
Public propertyIsAtLineStartPositionGets a value that indicates whether the current position is at the beginning of a line.
Public propertyLogicalDirectionGets the logical direction associated with the current position which is used to disambiguate content associated with the current position.
Public propertyParagraphGets the paragraph that scopes the current position, if any.
Public propertyParentGets the logical parent that scopes the current position.
Top

  NameDescription
Public methodCompareToPerforms an ordinal comparison between the positions specified by the current TextPointer and a second specified TextPointer.
Public methodDeleteTextInRunDeletes the specified number of characters from the position indicated by the current TextPointer.
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetAdjacentElementReturns the element, if any, that borders the current TextPointer in the specified logical direction.
Public methodGetCharacterRectReturns a bounding box (Rect) for content that borders the current TextPointer in the specified logical direction.
Public methodGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodGetInsertionPositionReturns a TextPointer to the closest insertion position in the specified logical direction.
Public methodGetLineStartPosition(Int32)Returns a TextPointer to the beginning of a line that is specified relative to the current TextPointer.
Public methodGetLineStartPosition(Int32, Int32)Returns a TextPointer to the beginning of a line that is specified relative to the current TextPointer, and reports how many lines were skipped.
Public methodGetNextContextPositionReturns a pointer to the next symbol in the specified logical direction.
Public methodGetNextInsertionPositionReturns a TextPointer to the next insertion position in the specified logical direction.
Public methodGetOffsetToPositionReturns the count of symbols between the current TextPointer and a second specified TextPointer.
Public methodGetPointerContextReturns a category indicator for the content adjacent to the current TextPointer in the specified logical direction.
Public methodGetPositionAtOffset(Int32)Returns a TextPointer to the position indicated by the specified offset, in symbols, from the beginning of the current TextPointer.
Public methodGetPositionAtOffset(Int32, LogicalDirection)Returns a TextPointer to the position indicated by the specified offset, in symbols, from the beginning of the current TextPointer and in the specified direction.
Public methodGetTextInRun(LogicalDirection)Returns a string containing any text adjacent to the current TextPointer in the specified logical direction.
Public methodGetTextInRun(LogicalDirection, Char[], Int32, Int32)Copies the specified maximum number of characters from any adjacent text in the specified direction into a caller-supplied character array.
Public methodGetTextRunLengthReturns the number of Unicode characters between the current TextPointer and the next non-text symbol, in the specified logical direction.
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodInsertLineBreakInserts a line break at the current position.
Public methodInsertParagraphBreakInserts a paragraph break at the current position.
Public methodInsertTextInRunInserts the specified text into the text Run at the current position.
Public methodIsInSameDocumentIndicates whether the specified position is in the same text container as the current position.
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodToStringThis type or member supports the Windows Presentation Foundation (WPF) infrastructure and is not intended to be used directly from your code. (Overrides Object.ToString().)
Top

The TextPointer class introduces the following terminology:

  • Position - Inherently, a TextPointer always points to a position in content. Such positions either fall between characters in the content, or between flow content element tags that define structure for the content.

  • Current Position - Because a TextPointer always indicates a position, and because many of the operations that can be performed through a TextPointer are relative to the position currently pointed to by the TextPointer, it makes sense to simply refer to the position indicated by a TextPointer as the current position.

  • Insertion Position - An insertion position is a position where new content may be added without breaking any semantic rules for the associated content. In practice, an insertion position is anywhere in content where a caret may be positioned. An example of a valid TextPointer position that is not an insertion position is the position between two adjacent Paragraph tags (that is, between the closing tag of the preceding paragraph and the opening tag of the next paragraph).

  • Symbol - For the purposes of TextPointer operations that involve symbols, any of the following is considered to be a symbol:

  • Text Container - A text container is the element that forms the ultimate border for the flow content at hand; the position indicated by a TextPointer always falls within a text container. Currently, a text container must be either a FlowDocument or a TextBlock. Generally speaking, operations between TextPointer instances in different text containers are not supported.

  • Document - The content in a text container is referred to as a document, as in the IsInSameDocument method and the DocumentStart and DocumentEnd properties.

The TextPointer class is intended to facilitate traversal and manipulation of content that is represented by Windows Presentation Foundation (WPF) flow content elements; in general, such elements derive from TextElement. Some of the operations that TextPointer facilitates include the following:

The position and LogicalDirection indicated by a TextPointer object are immutable. When content is edited or modified, the position indicated by a TextPointer does not change relative to the surrounding text; rather the offset of that position from the beginning of content is adjusted correspondingly to reflect the new relative position in content. For example, a TextPointer that indicates a position at the beginning of a given paragraph continues to point to the beginning of that paragraph even when content is inserted or deleted before or after the paragraph.

The TextPointer class does not provide any public constructors. An instance of TextPointer is created by using properties or methods of other objects (including other TextPointer objects). The following list provides a few examples of methods and properties that create and return a TextPointer. This list is not exhaustive:

The following example demonstrates how to use a TextPointer to find a position just inside of the first Run element in a specified text container.

// This method returns the position just inside of the first text Run (if any) in a  
// specified text container.
TextPointer FindFirstRunInTextContainer(DependencyObject container)
{
    TextPointer position = null;

    if (container != null){
        if (container is FlowDocument)
            position = ((FlowDocument)container).ContentStart;
        else if (container is TextBlock)
            position = ((TextBlock)container).ContentStart;
        else 
            return position;
    }
    // Traverse content in forward direction until the position is immediately after the opening  
    // tag of a Run element, or the end of content is encountered. 
    while (position != null)
    {
        // Is the current position just after an opening element tag? 
        if (position.GetPointerContext(LogicalDirection.Backward) == TextPointerContext.ElementStart)
        {
            // If so, is the tag a Run? 
            if (position.Parent is Run)
                break;
        }

        // Not what we're looking for; on to the next position.
        position = position.GetNextContextPosition(LogicalDirection.Forward);
    }

    // This will be either null if no Run is found, or a position just inside of the first Run element in the 
    // specifed text container.  Because position is formed from ContentStart, it will have a logical direction 
    // of Backward. 
    return position;
} 

The following example implements a simplistic find algorithm using TextPointer facilities.

// This method will search for a specified word (string) starting at a specified position.
TextPointer FindWordFromPosition(TextPointer position, string word)
{
    while (position != null)
    {
         if (position.GetPointerContext(LogicalDirection.Forward) == TextPointerContext.Text)
         {
             string textRun = position.GetTextInRun(LogicalDirection.Forward);

             // Find the starting index of any substring that matches "word".
             int indexInRun = textRun.IndexOf(word);
             if (indexInRun >= 0)
             {
                 position = position.GetPositionAtOffset(indexInRun);
                 break;
             }
         }
         else
            position = position.GetNextContextPosition(LogicalDirection.Forward);
     }

     // position will be null if "word" is not found.
     return position; 
}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
Show:
© 2014 Microsoft