Articolo
11/18/2011

TextPointer.LogicalDirection Property

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Gets the logical direction associated with the current position, which is used to disambiguate content associated with the current position.

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

Syntax

'Declaration
Public ReadOnly Property LogicalDirection As LogicalDirection

public LogicalDirection LogicalDirection { get; }

Property Value

Type: System.Windows.Documents.LogicalDirection
The LogicalDirection value that is associated with the current position.

Remarks

As an example of how this property is used, the LogicalDirection of the TextPointer returned by a hit test method gives a hit that is between two characters of text. The logical direction specifies which of the two characters was actually hit—the left or the right.

Examples

The following code uses the LogicalDirection property to underline the last word in the RichTextBox. In this example, a space character is used as the word boundary. This code example is part of a larger example used in the TextPointer class.

Run this sample

    'This method underlines the last word in a RichTextBox
    Public Sub UnderlineLastWord()
        Dim EndofContent As TextPointer = MyRTB1.ContentEnd.GetNextInsertionPosition(LogicalDirection.Backward)
        Dim currentPointer As TextPointer = EndofContent.GetNextInsertionPosition(LogicalDirection.Backward)
        If (currentPointer Is Nothing) Then
            Return
        End If
        Dim currentChar As String = GetCurrentChar(MyRTB1, currentPointer, LogicalDirection.Backward)

        While ((currentChar <> " ") _
                    AndAlso (currentChar <> ""))
            currentPointer = currentPointer.GetNextInsertionPosition(LogicalDirection.Backward)
            currentChar = GetCurrentChar(MyRTB1, currentPointer, LogicalDirection.Backward)

        End While
        If (currentChar = " ") Then
            MyRTB1.Selection.Select(currentPointer.GetNextInsertionPosition(LogicalDirection.Forward), EndofContent)
        Else
            MyRTB1.Selection.Select(currentPointer, EndofContent)
        End If
        MyRTB1.Selection.ApplyPropertyValue(Run.TextDecorationsProperty, TextDecorations.Underline)
    End Sub

    Private Function GetCurrentChar(ByVal RTB As RichTextBox, ByVal pointer As TextPointer, ByVal direction As LogicalDirection) As String
        Dim nextPointer As TextPointer = pointer.GetNextInsertionPosition(direction)
        If (Not (nextPointer) Is Nothing) Then
            RTB.Selection.Select(pointer, nextPointer)
            If (RTB.Selection.Text.Length <> 0) Then
                Return RTB.Selection.Text(0).ToString
            End If
        End If
        Return ""
    End Function

//This method underlines the last word in a RichTextBox
public void UnderlineLastWord()
{
    TextPointer EndofContent = MyRTB1.ContentEnd.GetNextInsertionPosition(LogicalDirection.Backward);
    TextPointer currentPointer = EndofContent.GetNextInsertionPosition(LogicalDirection.Backward);

    if (currentPointer == null)
        return;

    string currentChar = GetCurrentChar(MyRTB1, currentPointer, LogicalDirection.Backward);

    while (currentChar != " " && currentChar != "")
    {
        currentPointer = currentPointer.GetNextInsertionPosition(LogicalDirection.Backward);
        currentChar = GetCurrentChar(MyRTB1, currentPointer, LogicalDirection.Backward);
    }

    if (currentChar == " ")
        MyRTB1.Selection.Select(currentPointer.GetNextInsertionPosition(LogicalDirection.Forward), EndofContent);
    else
        MyRTB1.Selection.Select(currentPointer, EndofContent);

    MyRTB1.Selection.ApplyPropertyValue(Run.TextDecorationsProperty, TextDecorations.Underline);
}

private string GetCurrentChar(RichTextBox RTB, TextPointer pointer, LogicalDirection direction)
{
    TextPointer nextPointer = pointer.GetNextInsertionPosition(direction);
    if (nextPointer != null)
    {
        RTB.Selection.Select(pointer, nextPointer);
        if (RTB.Selection.Text.Length != 0)
            return RTB.Selection.Text[0].ToString();
    }
    return "";
}

Version Information

Silverlight

Supported in: 5, 4

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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