title: Finding already existing value in Key Value pair
body: <p>I am storing a string and int value in Key value pair.  </p>
  
  <pre><code>var list = new List&lt;KeyValuePair&lt;string, int&gt;&gt;();
  </code></pre>
  
  <p>While adding i need to check if string(Key) already exists in list, if exists i need to add it to Value instead of adding new key.<br>
  How to check and add?</p>