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This article discusses how custom forms are implemented in Outlook and provides suggestions for addressing unexpected symptoms you may experience when you create a solution based on Outlook forms.
NOTE: Throughout this article there is an important distinction between the terms, "items" and "forms." An item refers to a "record" of information (a group of fields) in a folder. A form is basically the "user interface" for the item and does not typically contain any data. Instead, it is published in a folder or forms library for use with items in the folder.
When you create custom form solution with Outlook it is important to be able to recognize how Outlook is using your custom form in relation to the items in a folder.
A "Typical" Custom Forms SolutionIf you want to create a custom contact form to replace the default Outlook contact form, you would typically follow these steps:
For more information about working with message classes, please see the following article in the Microsoft Knowledge Base:
(https://support.microsoft.com/kb/201087/EN-US/ )OL2000: How to Update Existing Items to Use a New Custom Form
One-Off FormsIn the typical scenario above, information about the form (the form definition) is not saved with each item. The form is basically "linked" using the Message Class field. The size of a typical item may be 300 or 500 bytes.
NOTE: For purposes of simplicity, this article uses the term "linked form" to indicate a situation in which the form definition is not saved within an item and the Message Class field is set to use a custom form.
However, it is possible to have the form definition saved with an item. Items that have a custom form definition stored within them are referred to as being "one-offed" or "a one-off."
When a form is one-offed it may use the form definition that is stored with the item instead of the published form. If a form definition is saved with an item the item's Message Class is changed back to the default message class for that form type, such as IPM.Contact.
Standard Ways Forms Become One-OffsYou can specify that a form is a one-off by clicking to select the "Send form definition with item" check box on the form's Properties page when in design mode. You would typically do this when the form is not registered in a form library where the recipient has access to it. Selecting this option ensures that the person sees the custom form when the item is opened.
Items One-Offed UnexpectedlyAssume you have a linked forms scenario and you have 10 items already created that are using your published custom form. If you open one of the items and the form definition is somehow changed for that one particular item, Outlook may automatically one-off the item (create a one-off form) and save the form definition with the item. The Message Class field may change back to the default message class for that type of item, and the size of the item noticeably increases.
The following are known scenarios where items can be unexpectedly one-offed.
Typical SymptomsAlthough solutions and situations vary greatly, there are some signs to be aware of that can indicate that forms are becoming one-offed.
Identifying a One-Off ItemIf an item is unexpectedly one-offed and then you notice that the "Send form definition with item" check box is not selected, that does not necessarily mean the form definition is not saved with the item.
An item is a one-off if its Message Class field is the default message class for that type of item but when the item is opened the form used to display the item is a custom form.
When developing a folder-based solution, you may want to display the Message Class and Size fields in a table view so you can be sure that the items in the folder are behaving as you expect. Also, a change in the icon for an item oftentimes indicates a status change but you should restart Outlook to be sure the proper icon is being displayed.
Steps to Reproduce the ProblemMicrosoft provides programming examples for illustration only, without warranty either expressed or implied, including, but not limited to, the implied warranties of merchantability and/or fitness for a particular purpose. This article assumes that you are familiar with the programming language being demonstrated and the tools used to create and debug procedures. Microsoft support professionals can help explain the functionality of a particular procedure, but they will not modify these examples to provide added functionality or construct procedures to meet your specific needs.
If you have limited programming experience, you may want to contact a Microsoft Certified Partner or Microsoft Advisory Services. For more information, visit these Microsoft Web sites:
Microsoft Certified Partners - https://partner.microsoft.com/global/30000104
Microsoft Advisory Services - http://support.microsoft.com/gp/advisoryservice
For more information about the support options that are available and about how to contact Microsoft, visit the following Microsoft Web site:http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS
(http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS)The following steps illustrate how by adding a user-defined field to an item can create a one-off form.
WorkaroundIf you need to have a scenario where an item may become a one-off, you can work around the side-effects of a one-off item by resetting the message class field and then saving the item in code. As an example, use the following code instead of the code given above in the "Steps to Reproduce the Problem" section and the item may not enable the macro warning message.
NOTE: If you programmatically change the message class of an item, the size of the item is not reduced. There is no way to truly remove the unwanted form definition from an item other than creating a new item without the form definition and copying the data from the old item to the new one.
For additional information about available resources and answers to commonly asked questions about Microsoft Outlook 2000 solutions, please see the following article in the Microsoft Knowledge Base:
(https://support.microsoft.com/kb/146636/EN-US/ )OL2000: Questions About Custom Forms and Outlook Solutions
(http://go.microsoft.com/fwlink/?LinkId=151500)for other considerations.