Databinding expression for retrieving value of related collection using LINQ

Posted by joshb on Stack Overflow See other posts from Stack Overflow or by joshb
Published on 2009-04-11T15:12:49Z Indexed on 2010/04/20 12:03 UTC
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I have a GridView that is bound to a LINQDataSource control that is returning a collection of customers.

Within my DataGrid I need to display the home phone number of a customer, if they have one. The phone numbers of a customer are stored in a separate table with a foreign key pointing to the customer table.

The following binding expression gets me the first phone number for a customer:

<asp:TemplateField HeaderText="LastName" SortExpression="LastName">
   <ItemTemplate>
      <asp:Label ID="PhoneLabel" runat="server" Text='<%# Eval("Phones[0].PhoneNumber") %>'></asp:Label>
   </ItemTemplate>
</asp:TemplateField>

I need to figure out how to get the home phone number specifically (filter based on phone type) and handle the scenario where the customer does not have a home phone in the database. Right now it's throwing an out of range exception if the customer does not have any phone numbers.

I've tried using the Where operator with a lambda expression to filter the phone type but it doesn't work:

<%# Eval("Phones.Where(p => p.PhoneTypeId == 2).PhoneNumber") %>

Solutions or links to any good articles on the subject would be much appreciated.

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