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Different Ways of Passing Values between
Pages
Passing Values Using
Querystring
This is one of the very common method
of sending data from the source page to destination page when using
Response.Redirect() method. You can pass values like key=value by separating the
target page and querystring with a ? symbol.
For example,
Target.aspx?key=value
Multiple values can be separated by
& between them.
Target.aspx?key1=value&key2=value
In the target page, you can retreive
the passed values using the QueryString collection exposed by Request
object.
Strinng value =
Request.QueryString["val"]
Usage
Source.aspx
protected void btnRedirect_Click(object
sender, EventArgs e)
{
Response.Redirect("Destination.aspx?val=frompreviouspage");
}
Destination.aspx
protected void Page_Load(object sender,
EventArgs e)
{
Response.Write(Request.QueryString["val"]);
}
Passing Values Using
HttpContext
At times, we use Server.Transfer to
redirect the user from one page to another page. In this case, one cannot use
querystring because the Server.Transfer will redirect to the target page using
the same request in the server i.e. there will not be any roundtrip to the
client before redirecting and hence the context of the request in the target
page is same as the request in source page.
In this scenario, we can use the
HttpContext object to pass values from source page to destination page. The
HttpContext object exposes an Item collection which will accept name-value
pairs. This Item collection can be used to attach a value in source page and
retrieve it back from the destination page.
Usage
Source.aspx
protected void btnRedirect_Click(object
sender, EventArgs e)
{
HttpContext _context =
HttpContext.Current;
_context.Items.Add("val", "from
previouspage");
Server.Transfer("Destination.aspx");
}
Destination.aspx
protected void Page_Load(object sender,
EventArgs e)
{
HttpContext _context =
HttpContext.Current;
Response.Write(_context.Items["val"]);
}
Passing Values Using
Sessions
This is another option to send values
between pages or to put it correctly, persisting values across pages in ASP.Net.
You can put whatever values you want to send to the target page in a Session
variable and get it back using the same session variable. Remember, using
session variable has its own limitation. By default, it uses the ASP.Net process
memory and you will have to face the consequence of using it heavily for just
passing values from one page to another. Of course, you can configure the
ASP.Net to use SQL server or state server to resolve this. Using Session
variable is an option and hence it is discussed in this article. Understand the
consequence before using approach.
To put values in session,
Session["key"] = value
To get it back from session in target
page,
String val =
Session["key"].ToString();
Passing Values Using
Cookies
This is one another way which you can
use to pass values from a source page to destination page in ASP.Net. Remember,
like Session it also has its limitation where the cookies are gets stored in
clientside and it will be passed to target page. Refer the code
below,
Usage
Source.aspx
protected void btnRedirect_Click(object
sender, EventArgs e)
{
HttpCookie cookie = new
HttpCookie("PreviousPage");
cookie.Value =
txtValue.Text;
Response.Cookies.Add(cookie);
Response.Redirect("Destination.aspx");
}
Destination.aspx
protected void Page_Load(object sender,
EventArgs e)
{
if
(Request.Cookies["PreviousPage"] != null)
Response.Write(Request.Cookies["PreviousPage"].Value);
}
Refer here
to know more about cookies.
Passing Values Using Cross Page
Postback
Using cross page postback means posting
the source page to a different aspx page. By default, all aspx pages will post
to itself. You can understand this when you see the action attribute of form tag
which will have the value as the same page name. This means, clicking a submit
button on the page will post to the same page on the server. Coming to our
subject, you can use this technique to post the values in source page to a
destination page using cross page postback.
There are multiple ways of implementing
it. Some are below,
1. You can set the action attribute of form tag as Destination
page,
<form id="form1" runat="server"
action="Destination.aspx">
2. You can use jquery or javascript to chaneg action attibute of form
tag to destination page.
<script
src="../scripts/jquery-1.4.1.min.js"
type="text/javascript"></script>
<script
type="text/javascript">
$(document).submit(function()
{
$("form").attr("action",
"Destination.aspx");
});
</script>
When using any of these techniques
above, you can get source page posted values through the Request.Form
collection. For example,
Changing action using
jquery
<head runat="server">
<title></title>
<script
src="../scripts/jquery-1.4.1.min.js"
type="text/javascript"></script>
<script
type="text/javascript">
$(document).submit(function()
{
$("form").attr("action",
"Destination.aspx");
});
</script>
</head>
<body>
<form id="form1"
runat="server">
<div>
<asp:TextBox ID="txtValue"
runat="server"></asp:TextBox>
<input id="Submit1" type="submit"
value="Redirect" />
</div>
</form>
</body>
</html>
Changing the default action in form
tag
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server"
action="Destination.aspx">
<div>
<asp:TextBox ID="txtValue"
runat="server"></asp:TextBox>
<input id="Submit1" type="submit"
value="Redirect" />
</div>
</form>
</body>
</html>
To access the value posted in txtValue
in destination page when using any of the above 2 approach,
Destination.aspx
protected void Page_Load(object sender,
EventArgs e)
{
Response.Write(Request.Form["txtValue"].ToString());
}
The above approach will give
ViewStateMac failed error below because the source page viewstate is not valid
on destination page.
Validation of viewstate MAC failed. If
this application is hosted by a Web Farm or cluster, ensure that
<machineKey> configuration specifies the same validationKey and validation
algorithm. AutoGenerate cannot be used in a cluster.
To resolve this you need to set
EnableViewStateMac="false" in @Page directive. Or, you can use the new property
of the ASP.Net Button control called PostBackUrl released with ASP.Net
2.0.
To know more about this read Cross
Page Post Back in ASP.Net 2.0
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