Search a text in WPF RichTextBox & replace its font.

Question

Hi,
I m using WPF RichTextBox(System.Windows.Controls.RichTextBox) but i am not getting a direct way to Search a specific word mentioned in RichTextBox & change its FontStyle.
Please help..!!

Answer 1

Operating on the FlowDocument behind the RichTextBox works for me.

In the piece of code below, chatTextBox is a RichTextBox. DisplayMessage receives a message from a network socket, I'm not sure if the use of Dispatcher.Invoke is required in all situations, but it is in mine.

Each time I receive a message, I create a new Paragraph for it and append it to the text in the RTB. Whilst constructing the paragraph, I do any keyword colour replacements I wish to using regex.

The key is that a Paragraph is composed of a set of Run's. To change the FontStyle (Foreground colour in my case), you need to create a Run within the Run, so the XAML will go from <Run>Some text with blue text</Run> to <Run>Some text with </Run><Run Foreground="Blue">blue</Run><Run> text</Run>, where blue is the keyword, and Blue is the colour name.

There may be an easier way.. but it works for me...

public partial class MainWindow : Window
{
  private FlowDocument chatDoc;

  public MainWindow()
  {
    InitializeComponent();

    chatDoc = new FlowDocument();
    chatDoc.SetValue(Paragraph.LineHeightProperty, 1.0);
  }

  protected void DisplayMessage(string message)
  {
    try
    {
      this.Dispatcher.Invoke(System.Windows.Threading.DispatcherPriority.Normal,
      new UpdatePublicChatDelegate(UpdateChat), message);
    }
    catch (Exception e)
    {
      Console.WriteLine(e.TargetSite.Name);
      Console.WriteLine(e.Message);
    }
  }

  public void UpdateChat(string text)
  {
    chatDoc.Blocks.Add(ChatDocument.CreateChatDocument(text));

    this.Dispatcher.Invoke(System.Windows.Threading.DispatcherPriority.Normal,
    new UpdateChatDocDelegate(UpdateChatDoc));
  }

  public void UpdateChatDoc()
  {
    try
    {
      chatTextBox.Document = chatDoc;
      chatTextBox.ScrollToEnd();
    }
    catch (Exception e)
    {
      Console.WriteLine(e.Message);
      throw;
    }
  }
}

public class ChatDocument
{
  public static Paragraph CreateChatDocument(string text)
  {
    Paragraph para = new Paragraph();
    
    para.Inlines.Add(CreateChatRun(text));
    
    ReplaceKeywords(ref para);
    
    return para;
  }
  
  public static Run CreateChatRun(string text)
  {
    try
    {
      Color runColour = ClientSettings.Appearance.MessageText.Colour;
      Run chatRun = new Run(text);
      chatRun.Foreground = new SolidColorBrush(runColour);
      return chatRun;
    }
    catch (Exception e)
    {
      Console.WriteLine(e.Message);
    }
    return null;
  }
  
  public static void ReplaceKeywords(ref Paragraph para)
  {
    try
    {
      TextRange tr;
      string xamlString = TextRangeToXamlString(para, out tr);

      string curKeyword = string.empty;
      System.Text.RegularExpressions.MatchEvaluator CatchRun = delegate(System.Text.RegularExpressions.Match m)
      {
        string prepend = "";
        string append = "";
        if (m.Groups["prepend"].Length != 0)
        {
          prepend = m.Groups["prepend"].Value + "</Run>";
        }
        if (m.Groups["append"].Length != 0)
        {
          append = "<Run>" + m.Groups["append"].Value;
        }

        return String.Format("{0}<Run Foreground=\"" + ClientSettings.Keywords[curKeyword].ToString() + "\">{1}</Run>{2}", prepend, curKeyWord, append);
      };

      int replacementStartPos = xamlString.IndexOf("<Run>");
      foreach (KeyValuePair<string, Color> keyword in ClientSettings.Keywords)
      {
        curKeyword = keyword.Key;
        string regexMatch = @"(?<prepend>.*)" + System.Text.RegularExpressions.Regex.Escape(keyword.Key) + "(?<append>.*)";
        System.Text.RegularExpressions.Regex findLocalNick = new System.Text.RegularExpressions.Regex(regexMatch, System.Text.RegularExpressions.RegexOptions.IgnoreCase);
        xamlString = findLocalNick.Replace(xamlString, CatchRun, 1000, replacementStartPos);
      }
      xamlString = xamlString.Replace("<Run></Run>", "");
      XamlStringToTextRange(ref tr, xamlString);
    }
    catch (Exception e)
    {
      Console.WriteLine(e.Message);
    }
  }
  
  private static string TextRangeToXamlString(Paragraph para, out TextRange tr)
  {
    tr = new TextRange(para.ContentStart, para.ContentEnd);
    System.IO.MemoryStream ms = new System.IO.MemoryStream();
    tr.Save(ms, DataFormats.Xaml);
    return Encoding.UTF8.GetString(ms.ToArray());
  }
        
  private static void XamlStringToTextRange(ref TextRange tr, string xamlString)
  {
    System.IO.MemoryStream msOut = new System.IO.MemoryStream();
    System.IO.StreamWriter sw = new System.IO.StreamWriter(msOut);
    sw.Write(xamlString);
    sw.Flush();
    msOut.Seek(0, System.IO.SeekOrigin.Begin);
    tr.Load(msOut, DataFormats.Xaml);
  }
}

Answer 2

Thanks for replying bt m not familiar with C#.
I converted the code to VB.Net but its dificult for me to simulate..

I will explain my requirment once more.

my application is in WPF(VB.NET)

I will be having one list of Names(lstOfNames)

wen my screen gets displayed i will be havin one paragraph inside the RICHTEXTBOX(System.Windows.Controls.RichTextBox)
<RichTextBox Height="50" Name="rtb" Width="212" Margin="139,37,127,37" />

Now wat i need to do is if paragraph contains any name dat is in lstOfNames as well then change its fontstyle(either color/background) & then display it in RICHTEXTBOX

Answer 3

Hi,
Here is a small sample in vb

<Grid>
        <RichTextBox Height="165" Margin="27,12,62,85" Name="RichTextBox1" Width="189" />
        <Button Height="23" Margin="82,0,121,20" Name="Button1" VerticalAlignment="Bottom">Button</Button>
    </Grid>

Class Window1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles Button1.Click
        Dim objtextRange As TextRange
        Dim lstWordstoBeMatched As New List(Of String)
        lstWordstoBeMatched.Add("Hello")
        lstWordstoBeMatched.Add("to")
        Dim objWordStartPoint As TextPointer
        Dim objWordEndPoint As TextPointer

        objtextRange = New TextRange(RichTextBox1.Document.ContentStart, RichTextBox1.Document.ContentEnd)
        Dim strText As String
        strText = objtextRange.Text
        Dim lstMatchGroup As MatchCollection
        Dim objStart As TextPointer
        objStart = RichTextBox1.Document.ContentStart
        For Each strMatch In lstWordstoBeMatched
            lstMatchGroup = Regex.Matches(strText, strMatch)
            For Each objMatch As Match In lstMatchGroup
                objWordStartPoint = GoToPoint(objStart, objMatch.Index)
                objWordEndPoint = GoToPoint(objStart, objMatch.Index + objMatch.Length)
                objtextRange = New TextRange(objWordStartPoint, objWordEndPoint)
                objtextRange.ApplyPropertyValue(TextElement.FontWeightProperty, FontWeights.Bold)
            Next
        Next

    End Sub

    Private Sub Window1_Loaded(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles MyBase.Loaded
        RichTextBox1.Document.Blocks.Clear()
        Dim obj As New Paragraph
        obj.Inlines.Add("Hello weelcome to the program.Hello how are you.to the message")
        RichTextBox1.Document.Blocks.Add(obj)
    End Sub


    Public Function GoToPoint(ByVal start As TextPointer, ByVal x As Integer) As TextPointer
        Dim out As TextPointer = start
        Dim i As Integer = 0
        Do While i < x
            If out.GetPointerContext(LogicalDirection.Backward) = TextPointerContext.Text Or _
                 out.GetPointerContext(LogicalDirection.Backward) = TextPointerContext.None Then
                i += 1
            End If
            If out.GetPositionAtOffset(1, LogicalDirection.Forward) Is Nothing Then
                Return out
            Else
                out = out.GetPositionAtOffset(1, LogicalDirection.Forward)
            End If
        Loop
        Return out
    End Function


End Class

Here I am entering the sample text in the code behind and the list of words to be made bold also .
Whatever is passed in the list will be make bold.

Hope it helps

---

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Answer 4

Tx.! :)

Answer 5

Hi,
See this link too for some help on it

Hope it helps

---

Please mark posts as answers/helpful if it answers your query. This would be helpful for others facing the same kind of problem