Wednesday, February 15, 2012

How to Cross Page Posting In ASP.NET Or Cross Page Postback

Posted by Manoj Ram on 6:36 AM with No comments so far
In this example i am going to describe Cross Page Posting or postback in ASP.NET 2.0 / 3.5 using C# and VB.NET.

Cross Page posting or cross page postback is used to submit a form on one page (say default.aspx) and retrieve values of controls of this page on another page (say Default2.aspx)

There are two ways we can use cross page postsbacks in ASP.NET 

<%@ Page Language="C#" AutoEventWireup="true"  
CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
First Name:
<asp:TextBox ID="txtFirstName" runat="server">
</asp:TextBox><br /><br />
Last Name:
<asp:TextBox ID="txtLastName" runat="server">
</asp:TextBox><br /><br /><br />
        
<asp:Button ID="btnSubmit" runat="server" 
            OnClick="btnSubmit_Click" 
            PostBackUrl="~/Default2.aspx"
            Text="Submit to Second Page" /><br />
</div>
</form>
</body>
</html>
Don't forget to set PostBackUrl Property of Button
PostBackUrl="~/Default2.aspx"

Now to retrieve values of textBoxes on Default2.aspx page, write below mentioned code in Page_Load event of second page (Default2.aspx)
C# code behind
01protected void Page_Load(object sender, EventArgs e)
02{
03    //Check whether previous page is cross page post back or not
04    if (PreviousPage != null && PreviousPage.IsCrossPagePostBack)
05    {
06        TextBox txtPbFirstName = (TextBox)PreviousPage.FindControl("txtFirstName");
07        TextBox txtPbLastName = (TextBox)PreviousPage.FindControl("txtLastName");
08        Label1.Text = "Welcome " + txtPbFirstName.Text + " " + txtPbLastName.Text;
09    }
10    else
11    {
12        Response.Redirect("Default.aspx");
13    }
14}
VB.NET Code behind
01Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
02    'Check whether previous page is cross page post back or not
03    If PreviousPage IsNot Nothing AndAlso PreviousPage.IsCrossPagePostBack Then
04        Dim txtPbFirstName As TextBox = DirectCast(PreviousPage.FindControl("txtFirstName"), TextBox)
05        Dim txtPbLastName As TextBox = DirectCast(PreviousPage.FindControl("txtLastName"), TextBox)
06        Label1.Text = ("Welcome " & txtPbFirstName.Text & " ") + txtPbLastName.Text
07    Else
08        Response.Redirect("Default.aspx")
09    End If
10End Sub

If you are using masterpages then you need to write code to FindControl as mentioned below
1ContentPlaceHolder exampleHolder =(ContentPlaceHolder)Page.PreviousPage.Form.FindControl ("Content1"));
2TextBox txtExample = exampleHolder.FindControl("txtFirstName");

2nd Method
Using Property to expose and Consume values of TextBox
If we are using this method then we don't need to use FindControl method at all
For this we need to create property in code behind of the page to be cross page post back (Default.aspx)
Html of the page needs no changes ,
C# code behind for Default.aspx
01public TextBox pbTxtFirstName
02    {
03        get
04        {
05            return txtFirstName;
06        }
07    }
08 
09    public TextBox pbTxtLastName
10    {
11        get
12        {
13            return txtLastName;
14        }
15    }

VB.NET
01Public ReadOnly Property pbTxtFirstName() As TextBox
02    Get
03        Return txtFirstName
04    End Get
05End Property
06 
07Public ReadOnly Property pbTxtLastName() As TextBox
08    Get
09        Return txtLastName
10    End Get
11End Property
Now to retrieve or consume exposed properties on Second page we need to add below mentioned page directive in html source of Default2.aspx page(usually at the top of page) 
<%@ PreviousPageType VirtualPath="~/Default.aspx" %>
Now write this code in page_Load event of second page to retrieve values of controls
C# code
01protected void Page_Load(object sender, EventArgs e)
02{
03    if (PreviousPage != null && PreviousPage.IsCrossPagePostBack)
04    {
05        Label1.Text = "Welcome " + PreviousPage.pbTxtFirstName.Text + " " + PreviousPage.pbTxtLastName.Text;
06    }
07    else
08    {
09        Response.Redirect("Default.aspx");
10    }
11}
VB Code
1Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
2    If PreviousPage IsNot Nothing AndAlso PreviousPage.IsCrossPagePostBack Then
3        Label1.Text = ("Welcome " & PreviousPage.pbTxtFirstName.Text & " ") + PreviousPage.pbTxtLastName.Text
4    Else
5        Response.Redirect("Default.aspx")
6 
7    End If
8End Sub

Hope this helps

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