title: LINQ to find array indexes of a value
body: <p>Assuming I have the following string array:</p>
  
  <pre><code>string[] str = new string[] {"max", "min", "avg", "max", "avg", "min"}
  </code></pre>
  
  <p>Is it possbile to use LINQ to get a list of indexes that match one string?</p>
  
  <p>As an example, I would like to search for the string "avg" and get a list containing </p>
  
  <blockquote>
    <p>2, 4</p>
  </blockquote>
  
  <p>meaning that "avg" can be found at str[2] and str[4].</p>