title: Changing inline in flowdocument
body: <p>I have a flowdocument like this:</p>
  
  <pre><code>var mcFlowDoc = new FlowDocument();
  var para = new Paragraph();
  para.Inlines.Add(new Run("This is the first line."));
  para.Inlines.Add(new Run("This is the second line."));
  para.Inlines.Add(new Run("This is the third line."));
  mcFlowDoc.Blocks.Add(para);
  richTextBox.Document = mcFlowDoc;
  </code></pre>
  
  <p>I need to change the background of one of the lines by clicking on any part of that text.</p>
  
  <p>First of all I am trying to change the background of a given inline (regardless of mouse click), but I am unable to do it.</p>
  
  <p>Any help would be appreciated.</p>
  
  <p><strong>Edit:</strong>
  I could change the background color of a run, but then I had to add all runs again and redraw.
  I need it to work faster, so I'm just trying to change a run without adding all again.</p>