title: Merge duplicate data without affecting others in LINQ code
body: <p>Goal:<br>
  If any duplicate, it should be merged into one for instance if "_name: a", _quantity: 3" and "_name: a", _quantity: 6" should be merged into "_name: a", _quantity: 9" in the list with other data with duplicate or not.</p>
  
  <p>Problem:
  I have a list with lots of data and I don't know how to merge duplicate data into one unit + it should not affect others. If possible, would like everyting to be happened inte same list without creating more list to acheive the result.</p>
  
  <pre><code>List&lt;Sale&gt; myList = GetAllSalesList()
  
  
  public classs Sale
  {
       public string _name;
       public string _quantity;
  }
  </code></pre>