How to color different words with different colors in a RichTextBox while a user is writing and raise an event when that colored text is clicked

Question

When a user writes some words in a rich text box, if that word matches some specific word, than the color of the that word should automatically change.

When the user clicks on that particular colored text, it should raise an event.

Answer 1

1) An User inserts some text in a RichTextBox
2) If any word entered is part of a pre-defined list of words, that word should change color (define a color related to each word.
3) When a mouse click event is generated on a colored word, an event is raised.

Possible result:

Define a custom EventHandler with custom EventArgs:

public class WordsEventArgs : EventArgs
{
    private string word;
    public WordsEventArgs(string s) { word = s; }
    public string Word { get { return word; } set { word = value; } }
}

public delegate void WordsEventHandler(object sender, WordsEventArgs e);
public event WordsEventHandler WordClicked;

protected void OnWordClicked(WordsEventArgs e) => WordClicked?.Invoke(this, e);

Subscribe the event:

this.WordClicked += new WordsEventHandler(this.Word_Click);

Simple Class for the list of words:

public class ColoredWord
{
    public string Word { get; set; }
    public Color WordColor { get; set; }
}

public List<ColoredWord> ColoredWords = new List<ColoredWord>();

Fill the list with some words an related color, then bind it to a listbox:

FillColoredWords();

public void FillColoredWords()
{
    ColoredWords.Add(new ColoredWord { Word = "SIMPLE", WordColor = Color.Goldenrod });
    ColoredWords.Add(new ColoredWord { Word = "COLORED", WordColor = Color.Salmon });
    ColoredWords.Add(new ColoredWord { Word = "TEXT", WordColor = Color.DarkCyan });
    this.listBox1.DisplayMember = "Word";
    this.listBox1.DataSource = ColoredWords;
}

In the richTextBox1.KeyPress() event, evaluate if the last entered word is part of the list of words to color:

private void richTextBox1_KeyPress(object sender, KeyPressEventArgs e)
{
    int CurrentPosition = richTextBox1.SelectionStart;
    if (e.KeyChar == (char)Keys.Space && CurrentPosition > 0 && richTextBox1.Text.Length > 1)
    {
        int LastSpacePos = richTextBox1.Text.LastIndexOf((char)Keys.Space, CurrentPosition - 1);
        LastSpacePos = LastSpacePos > -1 ? LastSpacePos + 1 : 0;

        string LastWord = richTextBox1.Text.Substring(LastSpacePos, CurrentPosition - (LastSpacePos));
        ColoredWord result = ColoredWords.FirstOrDefault(s => s.Word == LastWord.ToUpper());

        richTextBox1.Select(LastSpacePos, CurrentPosition - LastSpacePos);
        if (result != null)
        {
            if (richTextBox1.SelectionColor != result.WordColor)
                richTextBox1.SelectionColor = result.WordColor;
        }
        else
        {
            if (richTextBox1.SelectionColor != richTextBox1.ForeColor)
                richTextBox1.SelectionColor = richTextBox1.ForeColor;
        }
        richTextBox1.SelectionStart = CurrentPosition;
        richTextBox1.SelectionLength = 0;
        richTextBox1.SelectionColor = richTextBox1.ForeColor;
    }
}

In the richTextBox1_MouseClick() event, verify whether the click is generated on a colored word.
It true, raise the custom OnWordClicked() event:

private void richTextBox1_MouseClick(object sender, MouseEventArgs e)
{
    if (richTextBox1.SelectionColor.ToArgb() != richTextBox1.ForeColor.ToArgb())
    {
        try
        {
            int WordInit = richTextBox1.Text.LastIndexOf((char)32, richTextBox1.SelectionStart);
            WordInit = WordInit > -1 ? WordInit : 0;
            int WordEnd = richTextBox1.Text.IndexOf((char)32, richTextBox1.SelectionStart);
            string WordClicked = richTextBox1.Text.Substring(WordInit, WordEnd - WordInit) + Environment.NewLine;
            OnWordClicked(new WordsEventArgs(WordClicked));
        }
        catch (Exception)
        {
            //Handle a fast doublelick: RTB is a bit dumb.
            //Handle a word auto-selection that changes the `.SelectionStart` value
        }
    }
}

In the custom event, add the clicked word to a textbox text:

private void Word_Click(object sender, WordsEventArgs e)
{
    textBox1.AppendText(e.Word);
}

Answer 2

first of all add an event to your rich box text changed,then you need to change the color of text if that is an specific word like for example : Munis , Ali

   private void Rchtxt_TextChanged(object sender, EventArgs e)
            {
                this.CheckKeyword("Munis", Color.Purple, 0);
                this.CheckKeyword("Ali", Color.Green, 0);
            }