title: Add() Performance : HashSet<T>, Dictionary<Key,Value> and List<T>
body: <p>What is the best performance optimized alternative to choose among <code>Dictionary&lt;TKey,TValue&gt;</code>, <code>HashSet&lt;T&gt;</code> and <code>List&lt;T&gt;</code> with respect to :</p>
  <blockquote>
  <p>Add values(without duplicates)</p>
  <p>LookUps</p>
  <p>Delete values.</p>
  </blockquote>
  <p>I have to avoid adding duplicate values to the collection I know HashSet is good, since it skips the add if a duplicate is detected, a dictionary on the other hand throws an exception if a duplicate is found. List will need an additional ifExists check on the existing items before adding the value. But adding values in a <code>HashSet&lt;T&gt;</code> without duplicates seems to take around 1 min for 10K records. Is there a way to optimize this.</p>