When developing an ASP.Net page I tend to pass a lot of data between pages. A lot of it comes from being fairly OO natured and wanting to have a page that displays a particular type of content.
There are lots of articles detailing how to pass data between pages that have a 1-1 relationship using the PreviousPage property and PreviousPageType directive. That is great for wizard style pages where there is only one page that is allowed to pass data to a particular page. However it’s not as helpful when the target page is meant to take input from multiple sources because you can only specify a single PreviousPageType directive.
The approach I take is interface based. The PreviousPage property is available whether or not the PreviousPageType directive is present in the page. All the PreviousPageType directive does is make the property strongly typed. Without it the directive it’s just typed as Page. To make it strongly typed, I create an interface that the calling page must implement and then attempt to cast the source page into the specific interface.
PartialPublic Class _Default
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim source As ITextSource = TryCast(Me.PreviousPage, ITextSource)
If source IsNot Nothing Then
Public Interface ITextSource
ReadOnly Property Text() As String
This gives us all of the benefits of using the PreviousPageType directive with just a few lines of overhead. It makes passing data between pages trivial.