Question

For my application, I have a page that redirects to another page (within the same application) via Server.Transfer. I need to do this because the original page has an object that I need to access by using the Page.PreviousPage property.

Once my “destination” page has been fully loaded, a local deep clone that I made of the source page’s object is suddenly released from memory once I perform a postback? Is this by design–something to do with the Server.Transfer?

An example…

Page1.aspx:

Public Structure myCustomObject
    Implements ICloneable
    Dim someField as String = "default value" ' Default value
    Public Function Clone() As Object Implements System.ICloneable.Clone
        Dim temp as new myCustomObject
        temp.someField = Me.someField
        Return temp
    End Function
End Structure

Dim obj As myCustomObject
Public ReadOnly Property objProp as myCustomObject
    Get
        Return obj
    End Get
End Property
objProp.someField = "changed value from source page"

Server.Transfer("page2.aspx", True)

---

Page2.aspx:

(onLoad)
Dim newObj As myCustomObject
newObj = Page.PreviousPage.objProp.Clone()
Debug.Write(newObj.someField) ' Output: "changed value from source page"

At this point, EVERYTHING works as it should. Stuff got cloned over correctly and all is well.

(Let's say this is on a button click event)
Debug.Write(newObj.someField) ' Output: "default value"<- This is NOT "changed value from source page" for some reason when it was working literally a few lines ago!

It’s around here that I get the problem. My guess is that the Server.Transfer stops any association with the source page after the new page loads.

Is there a better way for cross-page object passing?

Answer 1

Just pass a variable in the HttpContext, you will have to handle your casting, not sure what Page.PreviousPage is:

Current Page:

HttpContext CurrContext = HttpContext.Current;
CurrContext.Items.Add("PreviousPage", Page.PreviousPage);

Transfered to page:

HttpContext CurrContext = HttpContext.Current;
var previousPage = CurrContext.Items["PreviousPage"];

Sorry for the C#, there was no code and the question wasn’t marked with VB.NET when I answered. Someone feel free to convert.