DOCUMENT:Q190886  07-AUG-1998  [vbwin]
TITLE   :HOWTO: Manage State Between DHTML Page Designer Pages
PRODUCT :Microsoft Visual Basic for Windows
PROD/VER:
OPER/SYS:WINDOWS
KEYWORDS:

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The information in this article applies to:

 - Microsoft Visual Basic Professional and Enterprise Editions for
   Windows, version 6.0
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SUMMARY
=======

DHTML Applications, like other Internet applications, are stateless. For
example, if you navigate from Page1.HTM to Page2.HTM in your DHTML
Application, you can no longer access information stored in Page1.HTM. A
separate instance of your Visual Basic code behind the DHTML Application is
created for each page. The instance is destroyed when you navigate away
from a given page. In some cases, you may need to save some "state"
information that can be accessed by multiple pages.

To save state information in a DHTML application, you use the GetProperty
and PutProperty functions to store and retrieve data.

MORE INFORMATION
================

The GetProperty and PutProperty functions are part of the modDHTML module
that is added to your project when you create a new project using the DHTML
Application template. These functions are implemented in Visual Basic using
the client side cookies and are simpler to use then coding cookies
directly.

You store state information using the PutProperty function and retrieve the
information using the GetProperty function. Here are the declarations of
these functions:

   Public Sub PutProperty(objDocument As HTMLDocument,
                          strName As String,
                          vntValue As Variant,
                          Optional Expires As Date)
   
   Public Function GetProperty(objDocument As HTMLDocument,
                               strName As String) As Variant

Following are some important things to remember while using these
functions:

 - Pass BaseWindow.Document for objDocument.

 - Pass a unique key name in strName that identifies your property.

 - Pass the property value in vntValue. Use the same key to retrieve the
   value.

 - vntValue is a variant, but only string values should be stored because
   the values are stored in cookies. Do not pass object references.

 - The date and time passed in Expires should be in GMT.

 - Remember to stay within the cookie limits of the Browser. The cookie
   spec lists the following limits:

    - 20 cookies per server or domain
    - 4 KB per cookie
    - 300 total cookies

Example
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For example, suppose you want to build a simple application that will store
and retrieve data across page boundaries. The application will consist of
two pages: one to store values, and one to retrieve them.

The first page in the application contains a text field into which the end
user can enter a value, and a button that stores the value to the cookie.
The code for the button, called StoreButton1, would look like this:

   Private Function StoreButton1_onclick() As Boolean
       PutProperty BaseWindow.Document, "Property1", TextField1.Value
   End Function

The second page in the same application contains a button that, when
clicked, retrieves the property from the cookie. The code for that button,
called GetButton1, would look like this:

   Private Function GetButton1_onclick() As Boolean
      MyValue.innerText = "The value of the property is " & _
          GetProperty(BaseWindow.Document, "Property1")
   End Function

This function uses the innerText property of Dynamic HTML to replace the
contents of a DIV tag, called "MyValue," with a sentence that contains the
retrieved property.

Additional query words: kbdsi kbDSupport kbVBp kbVBp600 kbDHTML
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Platform          : WINDOWS
Issue type        : kbhowto

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