ListView in ASP.NET and DataKeyNames

Question

I have a ListView, which is bound with a list of 'A', which looks like this:

Class A
    Property Id as Integer
    Property TestStringA as String
    Property B as B
End Class

Class B
    Property Id as Integer
    Property TestStringB as String
End Class

In the ListView i can refer to 'link property' values (whats the correct term for this?):

<asp:ListView runat="server" ID="lwTest" ItemType="A">
    <LayoutTemplate>
        <tr runat="server" id="itemPlaceHolder"></tr>
    </LayoutTemplate>
    <ItemTemplate>
        <tr>
             <td><%# Item.TestStringA %></td>
             <td><%# Item.B.TestStringB %></td> (this is what I mean)
        </tr>
    </ItemTemplate>
</asp:ListView>

This is also working when using the Eval-method (if unable to use 'ItemType'):

<%# Eval(B.TestStringB) %>

I want to loop the ListView´s items and use the values from the container, without saving them in hidden fields (isn't that the purpose of 'DataKeyNames'?). The issue is, that I can not refer to a property of another object by it's link-attribute/property (in the example B.Id) in DataKeyNames. When I do like this, I get an error telling me that there´s no property called 'B.Id'):

<asp:ListView runat="server" ID="lwTest" ItemType="A" DataKeyNames"Id, B.Id">
    <LayoutTemplate>
        <tr runat="server" id="itemPlaceHolder"></tr>
    </LayoutTemplate>
    <ItemTemplate>
        <tr>
             <td><%# Item.TestStringA %></td>
             <td><%# Item.B.TestStringB %></td> (this is what I mean)
        </tr>
    </ItemTemplate>
</asp:ListView>

Does anyone know if it is possible to do this? I know that I can add readonly properties returning the value directly to the bound object (but I would like to avoid this if possible):

Class A
    Property Id as Integer
    Property TestStringA as String
    Property B as B
    ReadOnly Property BId as Integer
        Get
            Return B.Id
        End Get
    End Property
End Class

Class B
    Property Id as Integer
    Property TestStringB as String
End Class

Thank you in advance!

score 0 · Answer 1 · answered Dec 16 '13 at 15:41

First of all, you can only use direct properties of a class as your DataKeyNames. With the Eval instruction you can go deeper(but I believe only one level).

What you can do is change what is shown in your list view through the code-behind.

To do this, add an ItemDataBound event. The data for the item that is being created can be found in e.Item.DataItem end will be of type A (do cast it before using).

You should be able to access your controls directly through e.Item (don't know which properties to use by heart on this one) and once you've found the correct cell, you can set any text to it you want and since you have the bound instance of A itself you can call any property or sub property you want without restrictions.

This function gets called for every entry in your ListView, so they should only provide you data of the current entry.

Hope this helps you solve your issue.

Thank you for your answer. Since it is not possible to do what I want within DataKeyNames, I have resolved it by adding ReadOnly properties which are returning the values from the linked properties. By the way - you CAN go deeper than one level by Eval (or the new binding-function that is included in ASP.NET 4.5 that I am using in my approach above, which also serves you with IntelliSense). Finally, I know about ItemDataBound - but in this specific case I wanted a solution without using it :) — thbaan, Dec 16 '13 at 15:54

ListView in ASP.NET and DataKeyNames

1 Answers1