HOWTO: Persisting Values Without Sessions
The information in this article applies to:
- Active Server Pages
- Microsoft Active Server Pages,
versions 1.0, 1.0b
- Microsoft Visual Studio versions
97, 97sp1, 97sp2, 97sp3
Summary
When developing Web sites with HTML forms you may need to keep
track of information entered by a user for use at a later time.
This process is called persisting values.
Active Server Pages (ASP) provides Session variables to facilitate
this; however, these require the use of session IDs. This article
describes methods of storing form values without using session cookies.
More Information
Three methods are commonly used to persist values when developing
in HTML:
Store the Values in Hidden Form Fields Storing the values
in hidden fields keeps the values out of sight, but intact. A user
submits a form, the form values are read and immediately written
back out again into an HTML hidden form field. This way, they get
carried along with the other fields when that form is submitted.
An example of this can be seen with the following three pages:
<%@ LANGUAGE="VBSCRIPT" %>
<!-- This is FORM1.HTM -->
<HTML>
<HEAD><TITLE>FORM1.HTM</TITLE></HEAD>
<BODY>
<Form Action=Form2.asp Method=Post>
<Input Type=Text Value="Page1 Value" Name="Value1"><P>
<Input Type=Submit Name=btnSubmit>
</Form>
</BODY>
</HTML>
<!-- This is FORM2.ASP -->
<%@ LANGUAGE="VBSCRIPT" %>
<%
Response.Cookies("Value1") = Request("Value1")
' If you wish to have the value persisted beyond the current visit,
' you must also assign an expiration date as follows:
Response.Cookies("Value1").Expires = "July 31, 1998"
%>
<HTML>
<HEAD><TITLE>FORM2.ASP</TITLE></HEAD>
<BODY>
<Form Action=Form3.asp Method=Post>
<Input Type=Text Value="Page2 Value" Name="Value2"><P>
<Input Type=Submit Name=btnSubmit>
</Form>
</BODY>
</HTML>
<!-- This is FORM3.asp -->
<%@ LANGUAGE="VBSCRIPT" %>
<HTML>
<HEAD><TITLE>FORM3.asp</TITLE></HEAD>
<BODY>
Value 1 = <%= Request("Value1") %><BR>
Value 2 = <%= Request("Value2") %><BR>
</BODY>
</HTML>
Append the Values to the URL This technique is very similar
to the first method, but instead of passing the values in hidden
variables, the values are appended to the end of the URL and submitted.
The disadvantage of this technique is imposed by the size limitations
on a URL, which can vary from browser to browser. Additionally,
any information, private or otherwise, will be readily visible to
the user. The following pages demonstrate this technique:
<!-- This is FORM1.HTM -->
<%@ LANGUAGE="VBSCRIPT" %>
<HTML>
<HEAD><TITLE>FORM1.HTM</TITLE></HEAD>
<BODY>
<Form Action=Form2.asp Method=Post>
<Input Type=Text Value="Page1 Value" Name="Value1"><P>
<Input Type=Submit Name=btnSubmit>
</Form>
</BODY>
</HTML>
<!-- This is FORM2.asp -->
<%@ LANGUAGE="VBSCRIPT" %>
<HTML>
<HEAD><TITLE>FORM2.asp</TITLE></HEAD>
<BODY>
<Form Action="Form3.asp?value1=<%=
Server.URLEncode(Request("Value1"))
%>" Method=Post>
<Input Type=Text Value="Page2 Value" Name="Value2"><P>
<Input Type=Submit Name=btnSubmit>
</Form>
</BODY>
</HTML>
<!-- This is FORM3.asp -->
<%@ LANGUAGE="VBSCRIPT" %>
<HTML>
<HEAD><TITLE>FORM3.asp</TITLE></HEAD>
<BODY>
Value 1 = <%= Request("Value1") %><BR>
Value 2 = <%= Request("Value2") %><BR>
</BODY>
</HTML>
Writing Your Own Cookie This method is least commonly used
because it requires that information be written back to the client
machine. The only reason to use this method over normal Session
based variable is to retain information for a later visit by the
browser. This alleviates your need to keep the information on the
Web server:
<!-- This is FORM1.HTM -->
<%@ LANGUAGE="VBSCRIPT" %>
<HTML>
<HEAD><TITLE>FORM1.HTM</TITLE></HEAD>
<BODY>
<Form Action=Form2.asp Method=Post>
<Input Type=Text Value="Page1 Value" Name="Value1"><P>
<Input Type=Submit Name=btnSubmit>
</Form>
</BODY>
</HTML>
<!-- This is FORM2.ASP -->
<%@ LANGUAGE="VBSCRIPT" %>
<% Response.Cookies("Value1") = Request("Value1") %>
<HTML>
<HEAD><TITLE>FORM2.ASP</TITLE></HEAD>
<BODY>
<Form Action=Form3.asp Method=Post>
<Input Type=Text Value="Page2 Value" Name="Value2"><P>
<Input Type=Submit Name=btnSubmit>
</Form>
</BODY>
</HTML>
<!-- This is FORM3.ASP -->
<%@ LANGUAGE="VBSCRIPT" %>
<HTML>
<HEAD><TITLE>FORM3.ASP</TITLE></HEAD>
<BODY>
Value 1 = <%= Request.Cookies("Value1") %><BR>
Value 2 = <%= Request("Value2") %><BR>
</BODY>
</HTML>
REFERENCES
For the latest Knowledge Base artices and other support information
on Visual InterDev and Active Server Pages, see the following page
on the Microsoft Technical Support site:
http://support.microsoft.com/support/vinterdev/
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