title: how to filter and sum using linq
body: <p>what is the best LINQ approach for with no performance loss? how could we do the same thing using LINQ iterating the list only once?</p>
  
  <pre><code>class Employee  
  {  
      string name ...;  
      string age .....;  
      int empType ...;  
      int income ...;  
  }  
  
  List&lt;Employee&gt; myList ...;  
  List&lt;Employee&gt; toList...;  
  int totalIncomeOfToList = 0;  
  
  foreach(Employee emp in myList)  
  {  
      if(emp.empType == 1)  
      {  
          toList.Add(emp);  
          totalIncomeOfToList += emp.income;  
      }  
  }  
  </code></pre>