title: Replace string with string format
body: <p>I have a variable that holds string, lets say like this:</p>
  
  <p><code>string str = "/a/b/1/cdd/d.jpg"</code></p>
  
  <p>And I have string format, lets say like this:</p>
  
  <pre><code>string frmt = "/a/b/{0}/be/"
  </code></pre>
  
  <p>Now, I want to use frmt to replace chars in str, something like that:</p>
  
  <pre><code>string newstr = str.Replace(frmt);
  //result should be: /a/b/1/be/d.jpg
  </code></pre>
  
  <p>Does the .net framework has something like that? How can it be done easily?</p>
  
  <p>Thanks.</p>