如何在自定义控件中呈现数据绑定值？

Question

I'm placing a custom control inside of an existing repeater template.

<ItemTemplate>
  <custom:MyControl>
    <something>
      <%# Eval("Firstname") %>
    </something>
  </custom:MyControl>
</ItemTemplate>

Is there any way that I can somehow get the value of <%# Eval("Firstname") %> without adding it as a property to my custom control?

<custom:MyControl Firstname='<%# Eval("Firstname") %>' />

I have a bigger need, as in I want to define an entire html structured inner property inside of <something> and it will be a disaster to do this inside of a property.

So, my repeater is databound, and apparently the control I'm placing within it is not databound, yet the values can be passed through via the property tags...

I found another answer stating it wasn't possible, but it's also 5 year old question. Eval inside an ASP.net repeater doesn't work inside another control

Grasping at straws, hoping for a solution.

Answer 1

You have to create a templated User Control with properties having TemplateContainer attribute. See following article for an example.

Creating a Templated User Control

Answer 2

I was able to figure this out, and I'd say the only reason I didn't figure it out sooner is due to testing every combination of methods, but missing a vital element in each one.

<ParseChildren(False)>
Public Class Something
    Inherits Button ' Just picked something

    Public Property InnerStuff() AS String

    Protected Overrides Sub OnLoad(e As EventArgs)

        EnsureChildControls()

        If HasControls() Then

            ' Interesting, if Eval() has taken place, a 
            ' DataBoundLiteralControl is created as a child
            ' control.
            If TypeOf Controls(0) Is DataBoundLiteralControl Then
                Dim instance As DataBoundLiteralControl = CType(Controls(0), DataBoundLiteralControl)
                ' I can push the text into a property
                InnerStuff = instance.Text

            ' If no databinding occurred, it creates LiteralControl
            ElseIf TypeOf Controls(0) Is LiteralControl Then
                Dim instance As LiteralControl = CType(Controls(0), LiteralControl)
                InnerStuff = instance.Text
            End If

        MyBase.OnLoad(e)

    End Sub
End Class

Maybe there's a cleaner way, but this appears to be working, and my markup now looks like this:

<custom:MyControl>
    Inner text, with or without <%#Eval("...")%>
</custom:MyControl>