Using WebControlAdapter - CheckedChanged event not firing on RadioButton PostBack (WinForms)

[edit] I meant WebForms (in the title), not WinForms...

I am using a WebControlAdapter to render my radio buttons, but when I post (autoPostBack= True) my form back, the CheckedChange event is not firing (the PostBack is happening).  This is my render code

Imports System.Web.UI.WebControls.Adapters

Public Class myRadio
   Inherits WebControlAdapter

   Protected Overrides Sub RenderBeginTag(ByVal writer As System.Web.UI.HtmlTextWriter)
      ' MyBase.RenderBeginTag(writer)
   End Sub

   Protected Overrides Sub RenderEndTag(ByVal writer As System.Web.UI.HtmlTextWriter)
      ' MyBase.RenderEndTag(writer)
   End Sub

   Protected Overrides Sub RenderContents(ByVal output As HtmlTextWriter)
      Dim ctrl As RadioButton = CType(Me.Control, RadioButton)
      Dim sb As New StringBuilder
      Dim cntxt As HttpContext = HttpContext.Current
      Try
         If Page.IsPostBack Then
            If cntxt.Request.Form.Count > 0 Then
               Try
                  ctrl.Checked = CBool(cntxt.Request.Form(ctrl.GroupName) = ctrl.Text)
               Catch ex As Exception
                  '
               End Try
            End If
         End If
         sb.Append("<label><input class=""")
         sb.Append(ctrl.CssClass)
         sb.Append(""" type=""radio""")
         sb.Append(" name=""")
         sb.Append(ctrl.GroupName)
         sb.Append("""")
         sb.Append(" value=""")
         sb.Append(ctrl.Text)
         sb.Append("""")
         sb.Append(" id=""")
         sb.Append(ctrl.ID)
         sb.Append("""")
         If ctrl.Checked Then sb.Append(" checked=""checked"" ")
         If ctrl.AutoPostBack Then
            sb.Append(" onclick=""javascript&colon;setTimeout(&#39;__doPostBack(\&#39;" & ctrl.ID & "\&#39;,\&#39;\&#39;)&#39;, 0)"" ")
         End If
         sb.Append("> ")
         sb.Append(ctrl.Text)
         sb.Append("</label>")
      Catch ex As Exception
         sb = New StringBuilder
         sb.Append("Error building Control:<br />")
         sb.Append(ex.Message)
      End Try
      output.Write(sb.ToString)
   End Sub

End Class

I have my MyAdapters.browser file set up, and the radio button is rendering as I want, and on (auto)postback it shows the correct checked state, but the CheckedChanged event won't fire. What am I not doing right?