title: Formatting specifc lines of text in WPF RichTextBox
body: <p>In a WPF .NET 4.0 RichTextBox with the following text:</p>
  
  <p>Apple </p>
  
  <p>Cheese </p>
  
  <p>Orange</p>
  
  <p>Pear</p>
  
  <p>Chicken</p>
  
  <p>How would I programmatically with C#, (not with XAML markup), bold all lines that start with the character "C"?</p>
  
  <p>More generally, how do you get a reference to a given line of text from a RichTextBox and then apply some formatting to it?</p>