Cross-Page PostBack error when posted from one folder to another

I'm getting the 'Object reference not set to an instance of an object.' error on PreviousPage after using PostBackUrl.

I created a simple test page to recreate the problem, however it worked fine, until I moved the source and destination pages into different folders. Is this the reason the PreviousPage object is null? how do I fix it?

Both the folders the source and destination pages are in are in the root directory of the website.

Source Page: /companies/test.aspx

<asp:Content runat="server" ID="Content" ContentPlaceHolderID="FullPage">
    <asp:TextBox ID="Demo" runat="server"></asp:TextBox>
    <asp:LinkButton ID="testlink" Text="test" runat="server"  PostBackUrl="~/Documents/test2.aspx">
    TESTING
    </asp:LinkButton>
</asp:Content>

public string MyVariable
{
    get
    {
        return Demo.Text;
    }
}

D开发者_高级运维estination Page: /documents/test2.aspx

<%@ PreviousPageType VirtualPath="~/Companies/test.aspx"  %> 

<asp:Content runat="server" ID="Content" ContentPlaceHolderID="FullPage">
    <asp:Label ID="output" runat="server" />
</asp:Content>

protected void Page_Load(object sender, EventArgs e)
{
    string MyText = PreviousPage.MyVariable;
    output.Text = MyText;
}

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Solved: Problem was in the casing of the PostBackUrl and the actual Directory structure.