Asp.Net4u: Cross Page Posting PostBack In ASP.NET

Wednesday, October 31, 2012

Cross Page Posting PostBack In ASP.NET

In this example i am showing how to use Cross Page Posting or Postback In ASP.NET 2.0, 3.5, 4.0 Using C# And VB.NET. Cross Page posting 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

1st method
In this i've created a Default.aspx page with two textbox and one button , button click will post back to Default2.aspx and there we will retrieve and show values of both textboxes

Html source of Default.aspx page is like

<%@ 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

protected void Page_Load(object sender, EventArgs e)
{
    //Check whether previous page is cross page post back or not
    if (PreviousPage != null && PreviousPage.IsCrossPagePostBack)
    {
        TextBox txtPbFirstName = (TextBox)PreviousPage.FindControl("txtFirstName");
        TextBox txtPbLastName = (TextBox)PreviousPage.FindControl("txtLastName");
        Label1.Text = "Welcome " + txtPbFirstName.Text + " " + txtPbLastName.Text;
    }
    else
    {
        Response.Redirect("Default.aspx");
    }
}

VB.NET Code behind

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
    'Check whether previous page is cross page post back or not
    If PreviousPage IsNot Nothing AndAlso PreviousPage.IsCrossPagePostBack Then
        Dim txtPbFirstName As TextBox = DirectCast(PreviousPage.FindControl("txtFirstName"), TextBox)
        Dim txtPbLastName As TextBox = DirectCast(PreviousPage.FindControl("txtLastName"), TextBox)
        Label1.Text = ("Welcome " & txtPbFirstName.Text & " ") + txtPbLastName.Text
    Else
        Response.Redirect("Default.aspx")
    End If
End Sub

If you are using masterpages then you need to write code to FindControl as mentioned below

ContentPlaceHolder exampleHolder =(ContentPlaceHolder)Page.PreviousPage.Form.FindControl ("Content1"));
TextBox 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

public TextBox pbTxtFirstName
    {
        get
        {
            return txtFirstName;
        }
    }

    public TextBox pbTxtLastName
    {
        get
        {
            return txtLastName;
        }
    }

VB.NET

Public ReadOnly Property pbTxtFirstName() As TextBox
    Get
        Return txtFirstName
    End Get
End Property

Public ReadOnly Property pbTxtLastName() As TextBox
    Get
        Return txtLastName
    End Get
End 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

protected void Page_Load(object sender, EventArgs e)
{
    if (PreviousPage != null && PreviousPage.IsCrossPagePostBack)
    {
        Label1.Text = "Welcome " + PreviousPage.pbTxtFirstName.Text + " " + PreviousPage.pbTxtLastName.Text;
    }
    else
    {
        Response.Redirect("Default.aspx");
    }
}

VB Code

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
    If PreviousPage IsNot Nothing AndAlso PreviousPage.IsCrossPagePostBack Then
        Label1.Text = ("Welcome " & PreviousPage.pbTxtFirstName.Text & " ") + PreviousPage.pbTxtLastName.Text
    Else
        Response.Redirect("Default.aspx")
        
    End If
End Sub

Hope this helps

Asp.Net4u

Wednesday, October 31, 2012

Cross Page Posting PostBack In ASP.NET

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