Cross-page posting in ASP.NET: read the previous page's controls

ASP.NET · By the Postback Notes editorial team · Published 2026-09-29

Normally a Web Forms page posts back to itself. With cross-page posting, a button sends the form to a different page, which can then read the first page's controls through PreviousPage. It is a tidy way to build a search form whose results live on another page, without putting everything in the URL.

The source page

<%-- Search.aspx --%>
<asp:TextBox ID="txtTerm" runat="server" />
<asp:DropDownList ID="ddlScope" runat="server">
    <asp:ListItem Value="all">Everything</asp:ListItem>
    <asp:ListItem Value="docs">Documents only</asp:ListItem>
</asp:DropDownList>
<asp:Button ID="btnSearch" runat="server" Text="Search" PostBackUrl="~/Results.aspx" />

Expose the values through public properties in the code-behind, so the target page does not need to know control ids:

public partial class Search : Page
{
    public string Term => txtTerm.Text.Trim();
    public string Scope => ddlScope.SelectedValue;
}

The target page, strongly typed

<%@ Page Language="C#" CodeBehind="Results.aspx.cs" Inherits="Demo.Results" %>
<%@ PreviousPageType VirtualPath="~/Search.aspx" %>

public partial class Results : Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (PreviousPage != null && PreviousPage.IsCrossPagePostBack)
        {
            string term = PreviousPage.Term;   // typed as Demo.Search thanks to @PreviousPageType
            string scope = PreviousPage.Scope;
            lblInfo.Text = "Results for " + Server.HtmlEncode(term);
            RunSearch(term, scope);
        }
        else if (!IsPostBack)
        {
            Response.Redirect("~/Search.aspx", false);
            Context.ApplicationInstance.CompleteRequest();
        }
    }
}

When you read PreviousPage, ASP.NET creates an instance of Search, runs its life cycle up to LoadComplete with the posted data, and hands it to you. Its controls contain the values the user submitted. Validation has run on the source page too, so you can check PreviousPage.IsValid.

Without the directive: FindControl

if (PreviousPage != null)
{
    var box = (TextBox)PreviousPage.FindControl("txtTerm");
    string term = box?.Text;
}

If the source uses a master page, the controls sit inside a ContentPlaceHolder, and PreviousPage.FindControl will not find them directly: look them up through PreviousPage.Master.FindControl("MainContent").FindControl("txtTerm"). Public properties avoid this fragility.

Comparison

Technique	URL in the browser	Data
Cross-page post	The target page	Full form posted to the target
`Server.Transfer`	Still the source page	`PreviousPage` also available, no new request
Query string	Target page with parameters, bookmarkable	A few short values
Session	Any	Kept server-side across many requests

A cross-page post is a POST: refreshing the results page asks the browser to resend the form, and the results cannot be bookmarked. For a search page that users share, the query string is usually better.

Common mistakes

Reading PreviousPage when the user arrives by a link or a bookmark: it is null. Always check it, as above.
Forgetting that the source page's Page_Load runs again to build PreviousPage: expensive work there, such as database queries, runs twice. Guard it with if (!IsPostBack) or move it to event handlers.
Expecting IsPostBack to be true on the target page: for a cross-page post it is false; PreviousPage.IsCrossPagePostBack is true.

Official documentation

Microsoft Learn: Page.PreviousPage, Page.IsCrossPagePostBack, Button.PostBackUrl
Microsoft Learn: Cross-page posting in ASP.NET Web Pages