Simplify my class mapping common class properties between model and viewmodel classes
Providing 

var dogVms = new List&lt;MonthViewModel&gt;();


is meant to actually be 

var dogVms = new List&lt;DogViewModel&gt;();


Then to use LINQ you could do

List&lt;DogViewModel&gt; dogVms = (from dog in dogs select (DogViewModel)dog).ToList();