vb.net - custom templates issue with databinding expressions in repeater control - vb.net

Question

I'm new here but I've been browsing stackoverflow for a while when looking for answers.
Here's the problem : I'm trying to implement a custom repeater with multiple conditional templates to avoid as much tests in the templates as possible
As for now my ascx code looks like that :
<custom:Repeater runat="server">
<headerTemplate>...</headerTemplate>
<templates>
<custom:template match="[filter1]"><contents>[filter1] is true for <%# Container.DataItem.ID%></contents></custom:template>
<custom:template match="[filter2]"><contents>[filter2] is true for <%# Container.DataItem.ID%></contents></custom:template>
</templates>
</custom:Repeater>
Besides that this syntax is too verbose, the following code works
<custom:template match="[filter1]"><contents><%# TypeOf Container is IDataItemContainer%></contents></custom:template>
But this code fails
<custom:template match="[filter1]"><contents>[filter1] is true for <%# Container.DataItem.ID%></contents></custom:template>
and I get the error message: : 'DataItem' is not a member of 'System.Web.UI.Control'.
It seems like vb tries to parse the template content at compile time instead of on databinding
Here are my vb classes
<ParseChildren(True, "contents")>
Public Class Template : Inherits WebControl : Implements ITemplate
Private _match As String
<PersistenceMode(PersistenceMode.Attribute)>
Public Property match() As String
Get
Return _match
End Get
Set(ByVal value As String)
'TODO compile filter as an expression
_match = value
End Set
End Property
Private _source As ITemplate
<PersistenceMode(PersistenceMode.Attribute)>
Public Property contents() As ITemplate
Get
Return Nothing
End Get
Set(ByVal value As ITemplate)
_source = value
End Set
End Property
Public Sub InstantiateIn(container As System.Web.UI.Control) Implements System.Web.UI.ITemplate.InstantiateIn
_source.InstantiateIn(container)
End Sub
End Class
<ParseChildren(True)>
Public Class ApplyTemplate : Inherits Repeater
_template as List(Of Template)
<PersistenceMode(PersistenceMode.InnerProperty), TemplateContainerAttribute(GetType(Template))>
Public Overloads Property templates() As List(Of Template)
Get
Return Nothing
End Get
Set(value As List(Of Template))
_templates = value
End Set
End Property
End Class
How can I add databinding expressions in my templates' content ?
Thanks in advance.
Max.
PS: Would it be possible (and how ;)) to compact the ascx code so it would look like this :
<custom:Repeater runat="server">
<headerTemplate>...</headerTemplate>
<custom:template match="[filter1]">[filter1] is true for <%# Container.DataItem.ID%></custom:template>
<custom:template match="[filter2]">[filter2] is true for <%# Container.DataItem.ID%></custom:template>
...
</custom:Repeater>

Answer 1

At last I had time to work on this again and thanks to this link (http://www.codeproject.com/Articles/21521/Creating-a-Templated-User-Control) I was able to implement my own custom repeater as I wanted to.
So now the aspx code looks like this
<custom:Repeater runat="server" >
<headerTemplate>...</headerTemplate>
<separatorTemplate on="1,9">some advertisement snippet</separatorTemplate>
<separatorTemplate every="2"><hr/></separatorTemplate>
<itemTemplate match="[filter1]"><source>[filter1] is true for <%# Container.DataItem.ID%></source></itemTemplate>
<itemTemplate match="[filter2]"><source>[filter2] is true for <%# Container.DataItem.ID%></source></itemTemplate>
...
</custom:Repeater>
The inner source tag is still necessary to allow code blocks in the template if needed.
If anybody knows how to remove it and still keep the feature with Metadata attributes, please comment.
So for the vb code here are the classes skeleton
Public Class Repeater
Inherits System.Web.UI.UserControl ' I use a UserControl so i can add support any html-bound attributes like class, style, data-*... without hardcoding them in the class
Private templates As New List(Of TemplateItem)
<PersistenceMode(PersistenceMode.InnerProperty)>
Public WriteOnly Property itemTemplate() As TemplateItem
Set(value As TemplateItem)
value.Container = Me 'to bind the container to the template instead of passing the reference on instanciation
templates.Add(value)
End Set
End Property
Public Overrides Sub DataBind()
If Not IsNothing(datasource) Then 'this to avoid nested controls Databind method to be called twice
[... iterate on dataitems]
[... template selection on best matching filters]
templates.instantiateFor(dataitem) ' to instanciate the template for the current item
[... iteration done]
MyBase.DataBind() ' to bind the newly created controls
End If
End Sub
...
End Class
'
<ParseChildren(True, "source")>
Public Class TemplateItem
Inherits Control
Friend Container As Repeater
'handle as many attributes as you want here
Private _matchExpression As String
<PersistenceMode(PersistenceMode.Attribute)>
Public Property match() As String
Get
Return _matchExpression
End Get
Set(value As String)
_matchExpression = value
End Set
End Property
'Now the simple part for parsing the inner code has a template
'I use the standard RepeaterItem class as the template container because i don't need more features for now
Private _source As ITemplate
<PersistenceMode(PersistenceMode.InnerDefaultProperty)>
<TemplateContainer(GetType(RepeaterItem))>
Public Property source() As ITemplate
Get
Return _source
End Get
Set(value As ITemplate)
_source = value
End Set
End Property
'now the part to instantiate as template for a given item
Public Sub instantiateFor(Item As Object, Optional itemIndex As Integer = -1)
Dim instantiator = New RepeaterItem(itemIndex, ListItemType.Item)
instantiator.DataItem = Item
_source.InstantiateIn(instantiator)
Container.Controls.Add(instantiator)
End Sub
End Class
Et voilà... at last !!
Hope this will help some