"Do Not Use Abstract Base Class in Design; But in Modeling/Analysis"

Selectively coloring text in RichTextBox

Try this:

static void HighlightPhrase(RichTextBox box, string phrase, Color color) {
  int pos = box.SelectionStart;
  string s = box.Text;
  for (int ix = 0; ; ) {
    int jx = s.IndexOf(phrase, ix, StringComparison.CurrentCultureIgnoreCase);
    if (jx < 0) break;
    box.SelectionStart = jx;
    box.SelectionLength = phrase.Length;
    box.SelectionColor = color;
    ix = jx + 1;
  }
  box.SelectionStart = pos;
  box.SelectionLength = 0;
}

...

private void button1_Click(object sender, EventArgs e) {
  richTextBox1.Text = "Aardvarks are strange animals";
  HighlightPhrase(richTextBox1, "a", Color.Red);
}

RichTextBox color specific line

You are missing the else condition, also do it for each line within TexBox like below

string text = richTextBox1.Text;
foreach (var line in richTextBox1.Lines)
{
  if (line.Contains("#"))
  {
    int firstcharindex = richTextBox1.GetFirstCharIndexOfCurrentLine();
    int currentline = richTextBox1.GetLineFromCharIndex(firstcharindex);
    richTextBox1.Select(firstcharindex, 10);
    richTextBox1.SelectionColor = Color.Red;
    richTextBox1.DeselectAll();
    richTextBox1.Select(richTextBox1.Text.Length, 0);
  }
  else
  {
    int firstcharindex = richTextBox1.GetFirstCharIndexOfCurrentLine();
    int currentline = richTextBox1.GetLineFromCharIndex(firstcharindex);
    richTextBox1.Select(firstcharindex, 10);
    richTextBox1.SelectionColor = Color.Black;
    richTextBox1.DeselectAll();
    richTextBox1.Select(richTextBox1.Text.Length, 0);
  }
}

Inserting Colored text into a RichTextBox

Why don't you use a syntax highlighting control for Windows Forms such as the following ones ?

http://scintillanet.codeplex.com/

https://code.google.com/p/alsing/wiki/SyntaxBox

The first one has SQL support, it took me less time than writing this post to get the following result using their demo app.:

RichTextBox text coloring has different behavior when added to the Form constructor

It seems the reason is Control's Handle has not been created yet. It is created only when you first call to AppendText. though it shouldn't be a problem(I'll get back if I find why that's a problem).

To fix it, just force the creation of handle. You do this by requesting the Handle property.

var handle = richTextBox1.Handle;//Force create handle
for (int i = 0; i < words.Length; i++)
{
    string word = words[i];
    Color color = colors[i];

    richTextBox1.SelectionBackColor = color;
    richTextBox1.AppendText(word);
    richTextBox1.SelectionBackColor = Color.AliceBlue;
    richTextBox1.AppendText(" ");

}

Coloring richtextbox based programming

You are aware that String.Contains does not check for words, aren't you?

If you use String.Contains("able"), then indeed you will find the word "able", but you'll also find words like "disabled", "sable" and "IEquatable".

To check for words you'll need a regular expression.

Whenever you need to process sequences of something, LINQ is your friend. Consider to familiarize yourself with the possibilities of LINQ.

Introduction of LINQ

Using Regular expressions and LINQ I could colorize the complete works of shakespeare (over five million characters) in about 5 seconds

// on load form: fill the rich text box with
// the complete works of William Shakespeare
private async void Form1_Load(object sender, EventArgs e)
{
    const string completeShakespeare = "http://www.gutenberg.org/cache/epub/100/pg100.txt";
    using (var downloader = new HttpClient())
    {
        this.richTextBox1.Text = await downloader.GetStringAsync (completeShakespeare);
    }
}

// on button click: mark all "thee" red
private void button1_Click(object sender, EventArgs e)
{
    var stopwatch = Stopwatch.StartNew();
    this.Colorize2("thee", Color.Red);
    var elapsed = stopwatch.Elapsed;
    Debug.WriteLine ("Coloring a text with {0} characters took {1:F3} sec",
        this.richTextBox1.Text.Length,
        elapsed.TotalSeconds);
}

private void Colorize2(string word, Color color)
{
    string regString = String.Format(@"\b{0}\b", word);
    // regex: match substring that match word,
    // with boundaries to non alphanumeric characters like space and \n \r \t

    var regex = new Regex(regString, RegexOptions.IgnoreCase);
    var matches = regex.Matches(richTextBox1.Text);
    foreach (Match match in matches.Cast<Match>())
    {
        this.richTextBox1.Select(match.Index, match.Length);
        this.richTextBox1.SelectionColor = color;
    }
}

How to retain colors of texts in rich text box?

You shouldn't use Parent property to hide, but Visible property instead.

If you hide a richtextbox using richTextBox.Visible = false it keeps its formatting (tested).

EDIT :

as discussed in the comments below, I suggest you to use only one RichTextBox and store several Rtf strings in a Dictionary (or Hashtable) to mimic the existence of different RichTextBox'es.

An example of what I mean can be found Here

Coloring certain words in a RichTextBox

im going to answer my question by myself!
Finally i found a great solution for my problem.

I`ve found a great powerfull UserControl on code-projekt
http://www.codeproject.com/Articles/42490/Using-AvalonEdit-WPF-Text-Editor

My way to the finall solution was:

Adding this to my .xml

xmlns:avalonEdit="http://icsharpcode.net/sharpdevelop/avalonedit"

And this

<avalonEdit:TextEditor  Visibility="Hidden" x:Name="RTBAuftragNEU" Margin="32,413,243,279" KeyDown="RTBKunde_KeyDown" Panel.ZIndex="1" VerticalScrollBarVisibility="Disabled" HorizontalScrollBarVisibility="Disabled" > </avalonEdit:TextEditor>

Then put this to my class where i need it.

        using (Stream s = System.Reflection.Assembly.GetExecutingAssembly().GetManifestResourceStream("ConsultingControls.highlight.xshd"))
        {
            using (XmlTextReader reader = new XmlTextReader(s))
            {
                RTBAuftragNEU.SyntaxHighlighting = HighlightingLoader.Load(reader, HighlightingManager.Instance);
            }
        }

Dont forget to create the XSHD file for the Syntax, you will find a complete tutorial on the codeproject site.

greetings,
fridolin

Change color and font for some part of text in WPF C#

If you just want to do some quick coloring, the simplest solution may be to use the end of the RTB content as a Range and apply formatting to it. For example:

TextRange rangeOfText1 = new TextRange(richTextBox.Document.ContentEnd, richTextBox.Document.ContentEnd);
rangeOfText1.Text = "Text1 ";
rangeOfText1.ApplyPropertyValue(TextElement.ForegroundProperty, Brushes.Blue);
rangeOfText1.ApplyPropertyValue(TextElement.FontWeightProperty, FontWeights.Bold);

TextRange rangeOfWord = new TextRange(richTextBox.Document.ContentEnd, richTextBox.Document.ContentEnd);
rangeOfWord.Text = "word ";
rangeOfWord.ApplyPropertyValue(TextElement.ForegroundProperty, Brushes.Red);
rangeOfWord.ApplyPropertyValue(TextElement.FontWeightProperty, FontWeights.Regular);

TextRange rangeOfText2 = new TextRange(richTextBox.Document.ContentEnd, richTextBox.Document.ContentEnd);
rangeOfText2.Text = "Text2 ";
rangeOfText2.ApplyPropertyValue(TextElement.ForegroundProperty, Brushes.Blue);
rangeOfText2.ApplyPropertyValue(TextElement.FontWeightProperty, FontWeights.Bold);

If you are looking for a more advanced solution, I suggest reading this Microsoft Doc about Flow Document, as it gives you a great flexibility in formatting your text.

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