title: Linq select strings from list when condition is met and save the index
body: <p>I have a list of strings </p>
  
  <p><code>List&lt;string&gt; lstOne = new List&lt;string&gt;() { "January:1", "February", "March:4"};</code></p>
  
  <p>And I am filtering the strings that contain : with this code</p>
  
  <p><code>var withcolumns = lstOne.Find(t =&gt; t.Contains(':'));</code></p>
  
  <p>and I am getting a new list with <code>{ "January:1", "March:4"}</code></p>
  
  <p>I want to select in a new list the values <code>January:1</code> and <code>March:4</code> but also save the indexes of then in the previous list so the result would be</p>
  
  <blockquote>
    <p>"0" "January:1" <br/>
    "2" "March:4"</p>
  </blockquote>
  
  <p>I can be simple or complicated but right now my brain is not functioning to solve this issue.</p>