Question

I am trying to figure out how to get at an anonymous typed object’s properties, when that anonymous type isn’t created in the current function.

Specifically, I am binding an ASP.NET ListView to LINQ resultset, then trying to process each item in the ItemDataBound event.

Option Explicit On
Option Strict On

Class MyPageClass

    Private Sub Bind()
        Dim items As ItemData = FetchItemData()

        Dim groups = From s In items Group s By Key = s.GroupId Into Group _
                Select GroupID = Key, GroupData = Group

        ' This works fine:
        Dim groupId As Integer = groups(0).GroupID

        lvGroups.DataSource = groups
        lvGroups.DataBind()
    End Sub

    Private Sub lvGroups_ItemDataBound(ByVal sender As Object, ByVal e As ListViewItemEventArgs) Handles lvGroups.ItemDataBound
        If e.Item.ItemType = ListViewItemType.DataItem Then
            Dim item As ListViewDataItem = DirectCast(e.Item, ListViewDataItem)
            Dim groupData = item.DataItem  ' This is the anonymous type {GroupId, GroupData}

            ' Next Line Doesn't Work 
            ' Error: Option Strict disallows late binding
            Dim groupId As Integer = groupData.GroupId

        End If
    End Sub

End Class

What do I need to do in lvGroups_ItemDataBound() to get at the item.DataItem.GroupId?

Answer 1

When you do the select, either create a class to select as (select new MyClass With { prop assignments here }) so that MyClass is an actual physical class that you can return. Or, you can use the DataBinder class as in:

DataBinder.GetPropertyValue(item.DataItem, "GroupId", null);

I believe I used that to get a value, which uses reflection to inspect the underlying type.