How can I change the selected text background color in Rich text box wpf c#

问题

How can I display html text in to RichTextBox control?

Actually I want to change the selected text background color in RichTextBox in C# wpf. I tried this code but it's not displaying formatted text.

Please help me... Thanks in advance!

void rtbTextEditor_SelectionChanged(object sender, RoutedEventArgs e)
{
    SelectionText = rtbTextEditor.Selection.Text.Trim();
    if (SelectionText != string.Empty)
    {
        if (VisualEditor.Document.Body != null)
        {
             //VisualEditor is web browser
             VisualEditor.Document.Body.InnerHtml = @"""<html><body><FONT style=""BACKGROUND-COLOR: #ffff00""><bold>""" + rtbTextEditor.Selection.Text + @"""</Bold></FONT></body></html>""";
             VisualEditor.Document.ExecCommand("SelectAll", false, null);
             rtbTextEditor.Document.Blocks.Add(new Paragraph(new Run(VisualEditor.Document.Body.InnerText.ToString())));
        }
    }
}

回答1:

private static TextPointer GetTextPointAt(TextPointer from, int pos)
  {
    TextPointer ret = from;
    int i = 0;

    while ((i < pos) && (ret != null))
    {
        if ((ret.GetPointerContext(LogicalDirection.Backward) == TextPointerContext.Text) || (ret.GetPointerContext(LogicalDirection.Backward) == TextPointerContext.None))
            i++;

        if (ret.GetPositionAtOffset(1, LogicalDirection.Forward) == null)
            return ret;

        ret = ret.GetPositionAtOffset(1, LogicalDirection.Forward);
    }

    return ret;
 }

 internal string Select(RichTextBox rtb, int offset, int length, Color color)
 {
    // Get text selection:
    TextSelection textRange = rtb.Selection;

    // Get text starting point:
    TextPointer start = rtb.Document.ContentStart;

    // Get begin and end requested:
    TextPointer startPos = GetTextPointAt(start, offset);
    TextPointer endPos = GetTextPointAt(start, offset + length);

    // New selection of text:
    textRange.Select(startPos, endPos);

    // Apply property to the selection:
    textRange.ApplyPropertyValue(TextElement.BackgroundProperty, new SolidColorBrush(color));

    // Return selection text:
    return rtb.Selection.Text;
 }

And then use it in this way (I'm selecting from first character to the fifth in RED) :

this.Select(this.myRichTextBox, 0, 5, Colors.Red);

来源：https://stackoverflow.com/questions/18015380/how-can-i-change-the-selected-text-background-color-in-rich-text-box-wpf-c-sharp

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