Vb.net - Using Eval With Sum() And Count() With EntityFramework And ListView?

I am working on my first project with the Entity Framework and am having some difficulty displaying advanced information with the EntityDataSource and a ListView.

For example, given the two entities:

Item
Name
Price
Order
Number
Items <---- Navigation Property to Items contained in the Order

I want to display a list of all orders with a column with the total number of items in the order and a column with the sum of the prices of all items in the order.

I am using an EntityDataSource configured as follows:

<asp:EntityDataSource ID="eds" runat="server" ConnectionString="name=NDSEntities"
DefaultContainerName="NDSEntities" EnableFlattening="False" Include="Items"
EntitySetName="Orders"></asp:EntityDataSource>

In the ItemTemplate of the ListView, I can write the order number as follows:

<%# Eval("Number") %>

I had trouble figuring out how to display a count of items in the order. I tried using Items.Count() function in select statement in the EntityDataSource but that didn't work. Eventually I figured out I could do the following in my ItemTemplate:

<%# Eval("Items").Count() %>

Now I am stuck trying to get the sum of the items. I am stuck here. I have tried using

<%# Eval("Items").Sum(Function(i) i.Price)%>

but I get the following error:

Public member 'Sum' on type 'EntityCollection(Of Item)' not found.

This confuses me because I know that Sum is a method of EntityCollection(Of ).

My two questions are as follows:

Am I getting the item count correctly?

How should I go about getting the sum of the prices of the items?