title: Append text in richTextBox from more sources in C
body: <p>I want to add some more strings from different sources together but I doesn't seem to work...<br>
  My code</p>
  
  <pre><code>int num = 0;
  string s = std::to_string(num);
  this-&gt;richTextBox1-&gt;Text = "Copying files... (" + s + "%)"; //this doesn't work
  </code></pre>
  
  <p>P.S: How to add codes like - <code>num = num + 1</code></p>