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

Given the requirements:

1) A User inserts some text in a RichTextBox Control.
2) If the word entered is part of a pre-defined list of words, that word should change color (so, define a relation between a word and a color).
3) When a mouse Click event is generated on a colored word, an event is raised, to notify which word was clicked.

Possible result (to replicate what's in the visual example):

Define a custom EventHandler with custom EventArgs:

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

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

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

Subscribe to 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, calling the FillColoredWords() method (in other words, handle a collection of objects that relate pieces of text with Color values):

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 KeyPress event, evaluate whether 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 MouseClick event, verify whether the event is generated on a colored word.
In that case, 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 DoubleClick: RTB is a bit dumb.
            //Handle a word auto-selection that changes the `.SelectionStart` value
        }
    }
}

In the custom event, you can append the clicked word to a TextBox (or do whatever else you want to do with it):

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);
            }