>I have several user controls (.ASCX) that exist on a page.
>
>In each, when an event happens (sqldatasource.inserted), I need to refresh the data in a control on the main (parent) page.
>

>Can someone explain this to me in some rational terms please?
>

(hopefully the VB code works - I'm normally working in C#)

.NET is strongly typed. That means you can't just grab a generic "Page" object from your ASCX class and call some method that you added in some subclass (your ASPX) of the page - it doesn't exist at the Page class level. Therefore you need to cast the Page object into your specific subclass of the page in order for it to "know"/compile that the method you're calling actually exists.

There are a few ways of doing this - which one you picks kind of depends on how the controls are going to be used, how much work you want to do, how tightly coupled you want to make things, etc.

Let's start with the one that's the least flexible, since it's the simplest. Assume your user control "knows" about the page it's going to be used on.

Let's suppose we have a public method in the ASPX code-behind that updates a control on the page.

public void UpdateText(string newText)
{
this.lblInfo.Text = newText;
}

We want to call this method from an ASCX page when something is changed. So from within the event we can do this:

MyWebPage page = Page as MyWebPage;

if (page != null)
   page.UpdateText("New Text");

Dim page As MyWebPage 

If Page <> Nothing Then
   page.UpdateText("New Text");
End If

That works OK but it limits the control to only working on that specific page. One way around that is to create an interface for the page which requires a page to implement an "UpdateText" method, ex:

   public interface IMyWebPage
    {
        void UpdateText(string newText);
    }

    public partial class MyWebPage : System.Web.UI.Page, IMyWebPage
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        public void UpdateText(string newText)
        {
            // Code specific to this page does something with the newText passed in.
        }
    }

Public Interface IMyWebPage
   Sub UpdateText(ByVal newText As String)
End Interface

Public Partial Class MyWebPage
   Inherits System.Web.UI.Page
   Implements IMyWebPage

  Public Sub UpdateText(ByVal newText As String)
     '' code spec.
   End Sub

We'd then change the code in the ASCX file to:

IMyWebPage page = Page as IMyWebPage;

if (page != null)
   page.UpdateText("New Text");

Dim page As IMyWebPage 

If Page <> Nothing Then
   page.UpdateText("New Text");
End If

Yet another way would be to create an event on the user control which fires, then bind to it from the ASPX page. If you need an example for that, let me know.