Q190886: HOWTO: Manage State Between DHTML Page Designer Pages

Article: Q190886
Product(s): Microsoft Visual Basic for Windows
Version(s): 6.0
Operating System(s): 
Keyword(s): 
Last Modified: 01-MAR-2002

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The information in this article applies to:

- Microsoft Visual Basic Professional Edition for Windows, version 6.0 
- Microsoft Visual Basic Enterprise Edition 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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Keywords          :  
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB600Search kbVB600
Version           : :6.0
Issue type        : kbhowto

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