title: Field concatenation based on group in LINQ
body: <p>I want concate a times field based on grouping of Userid and dates field using LINQ . i am using VS2010 C#(WPF).</p>
  
  <p>i have a collection in below format.</p>
  
  <p><img src="https://i.stack.imgur.com/FV8ja.jpg" alt="enter image description here"></p>
  
  <p>and want result like</p>
  
  <p><img src="https://i.stack.imgur.com/SKQt5.jpg" alt="enter image description here"></p>