Question

Ok, let’s imagine I have an object like this:

public class User {
    public int ID { get; set; }
    public String Name { get; set; }
    public String Surname { get; set; }
    public String Description { get; set; }
    public Location Location { get; set; }
}

Notice that the last property, is a Location type object. Let’s see the Location object:

public class Location {
    public String ID { get; set; }
    public String Address { get; set; }
    public String PostCode { get; set; }
}

Now I want to show a list of users in a gridview but instead of feeding it with a datareader or any data object, I want to use a List of Users Collection, so I call a method that gives me a List collection and databind the gridview like this:

gvUsers.DataSource = getUsers(); // This returns a List<User> collection.
gvUsers.DataBind();

Now, I’ve used some BoundFields and Templatefields to show the data and it works without problems, like this:

<asp:GridView ID="gvUsers" runat="server" AutoGenerateColumns="False" >
    <Columns>
        <asp:BoundField DataField="Name" HeaderText="Name" />
        <asp:BoundField DataField="Description" HeaderText="Description" />
        <asp:TemplateField HeaderText="Surname">
            <ItemTemplate>
                <asp:Label ID="lbSurname" runat="server" Text='<%# Eval("Surname") %>'></asp:Label>
                <asp:HiddenField ID="hdnUserId" runat="server" Value='<%# DataBinder.Eval(Container.DataItem, "ID") %>' />
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

The problem comes if I try to access the Location object properties, imagine this in the template field:

<asp:HiddenField ID="hdnLocationName" runat="server" Value='<%# DataBinder.Eval(Container.DataItem, "Location.PostCode") %>' />

That doesn’t work.

I don’t know if there is a way of doing that to show it using a template field. I also wonder if there is a way of doing it using a BoundField.

If it cannot be done just using the FrontEnd, can be done in the Backend in the gridView databound somehow? Should I use LINQ and set it on the select instead?

Answer 1

The Law of Demter applies. In short, you’ll have to make Postcode a property of user if you want to bind to it like that.

This page gives a nice example of Law of Demeter.