Visual Studio designer warning for custom web server control “Content is not allowed between the opening and closing tags for element <control-name>”

Question

The following code works as intended but I can't seem to get rid of the VS designer warning above.

Here's my custom web server control class:

<ParseChildren(True, "Content")>
Public Class Test
    Inherits WebControl

    Property Content As Control

    Private Sub Test_Init(sender As Object, e As EventArgs) Handles Me.Init
        Me.Controls.Add(Content)
    End Sub

End Class

Here is the markup:

<app:Test runat="server">
    This is a test<br />
    <asp:Button runat="server" Text="Click !" />
</app:Test>

I have tried different combinations of the following attributes on the Content property, but I can't get rid of the warning:

<PersistenceMode(PersistenceMode.InnerProperty), DesignerSerializationVisibility(DesignerSerializationVisibility.Content)>

Found a few sources which indicate that the above attributes should get rid of the warning. I've had no luck with these. Could someone please point me in the right direction?

Answer 1

So with a fresh start today, after the weekend, I finally got it to work as I intended.

I changed <ParseChildren(True, "Content")> to <ParseChildren(False), PersistChildren(True)> on the class declaration, removed the Content property and it started working as expected.

Note that <ParseChildren(False), PersistChildren(True)> will automatically place content inside the opening and closing tags into the child control collection of the custom control, making it easy to work with.