Transferring DropDownList values from one page to the next

Question

I have 2 pages, both with 3 similar DropDownLists. The first DropDownList needs to be populated before selecting the second, and the second before the third (which then populate

Answer 1

You can pass values from one page to the other using the PreviousPage parameter that asp.net provides you. A small example:

You set the second page on the submit button as:

PostBackUrl="SecondPage.aspx"

On SecondPage.aspx you declare where you can get informations

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

and you get them by...

if (Page.PreviousPage != null)
{
    if(Page.PreviousPage.IsCrossPagePostBack == true)
    {
        // and get the controls of the previous page as
        var SomeVariable = PreviousPage.DropDownlListId.SelectedValue;
    }
}

Some reference.
Cross-Page Posting in ASP.NET Web Pages
ASP.NET how to access public properties?
Cross-page postbacks and back again retaining data from source page
Cross-page posting. Is it a good pratice to use PreviousPage in Asp.net?