title: ToolTip appearing but not appearing again unless mouse moves
body: <p>I am using TextChanged event on a textbox to validate the contents. I am trying to make a tooltip appear if the user keys in illegal characters. This works fine the first time an illegal character is keyed in. IF I delete the illegal character and then add another illegal character the tooltip does not reappear. I have to move the mouse for the tooltip to reappear.</p>
  
  <p>What I want is a way to commulicate to the user that they have entered an illegal character in a textbox that cannot be used in a path.</p>
  
  <p>Why does the tooltip not reappear after another illegal character is entered?</p>
  
  <p>Code:</p>
  
  <pre><code>    // Initialization
      char[] illegalCharacters = Path.GetInvalidPathChars();
  
      //Event handler
      private void descriptionTextChanged(object sender, EventArgs e)
      {
          if (description.Text.Length &lt; 6)
          {
              description.BackColor = Color.LightPink;
              toolTip1.SetToolTip(description, @"Must be at least 6 characters long.");
          }
          else
          {
              description.BackColor = Color.White;
              foreach (char illegalCharacter in illegalCharacters)
              {
                  if (description.Text.Contains(illegalCharacter))
                  {
                      description.BackColor = Color.LightPink;
                      toolTip1.RemoveAll();
                      toolTip1.Show(@"Name may not contain a '&lt; , &gt; | or double quote.", description);
                      break;
                  }
              }
          }
      }
  </code></pre>