title: Why RichTextBox lose format after appending new String?
body: <p>I have aproblem with rich text box string color:</p>
  
  <p>I have the richtexbox that user type a message in it. I mark up each word that exist in my dictionary. I use this code for it:</p>
  
  <pre><code>  this.inputTextAreaRtb.Text=this.inputTextAreaRtb.Text.Remove(startCoordinate, endCoordinate - startCoordinate);
  
    this.inputTextAreaRtb.SelectionStart = this.inputTextAreaRtb.Text.Length;
   this.inputTextAreaRtb.SelectionLength = 0;
    this.inputTextAreaRtb.SelectionFont = new System.Drawing.Font(
    "David",
  12, FontStyle.Underline);   
     this.inputTextAreaRtb.SelectionColor = Color.DarkBlue;                                             
     this.inputTextAreaRtb.AppendText(_word);
    this.inputTextAreaRtb.SelectionColor = this.inputTextAreaRtb.ForeColor;
    this.inputTextAreaRtb.SelectionFont = new System.Drawing.Font(
     "David",
   12, FontStyle.Regular);      
  </code></pre>
  
  <p>But each time if I already marked up a word a loose formatting of words that already formatted.</p>
  
  <p>Any ideas of this problem? </p>