title: LinQ Group.Average truncates my values
body: <p>I've the following table structure:</p>
  
  <p>tempDt </p>
  
  <pre><code>col1 = Product (Integer)  
  col2 = Customer (Integer)  
  col3 = Center (Integer)  
  col4 = Date (Date)  
  col5 = Price (Double)  
  col6 = Sales (Double)  
  </code></pre>
  
  <p>This example rows: </p>
  
  <pre><code>1;1;1;01.01.2012;4.39;20000  
  1;1;1;02.02.2012;4.46;15000  
  1;1;1;03.03.2012;4.22;25000  
  </code></pre>
  
  <p>And the following Linq Query:  </p>
  
  <pre><code>For Each item In From u In tempDT.AsEnumerable
  Group u By Product = u("Product"), Customer = u("Customer"), Center = u("Center") Into Group
  Select Product, Customer, Center, Price = Group.Average(Function(g) g("Price")), Sales = Math.Round(Group.Sum(Function(g) CDbl(g("Sales"))), 2)
  
  tmpDt.Rows.Add(item.Product, item.Customer, item.Center, item.Price, item.Sales)
  Next
  </code></pre>
  
  <p>But as result I get the following line:
  1;1;1;4.0;60000</p>
  
  <p>Group.Average truncates the "Price" column, what's wrong?</p>