RichTextBox changing letters color - speed problem
<p>My file is 450 503 letters text. I have to change every letter (eg. 'b' - user choice) on another and mark it by set red color.
When I do it in that way:</p>

<pre><code> for(int i=0; i&lt;lenght; ++i) {
    this.rtb.Select(i, 1);
    this.rtb.SelectionColor = Color.Red;
    this.rtb.SelectedText = this.rtb.SelectedText;
    this.rtb.DeselectAll();
 }
</code></pre>

<p>It's too slooow - actually it never finished... (17min awaiting).
I have no idea how to speed it up.</p>
