Guidelines to create Outlook form regions
Applies to: 
Visual Studio 
Visual Studio for Mac
Note
This article applies to Visual Studio 2017. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here
The following information can help you optimize your form regions and avoid potential problems:
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For more information about form regions, see Create Outlook form regions.
Applies to: The information in this topic applies to VSTO Add-in projects for Outlook. For more information, see Features available by Office application and project type.
Use form region names
There are several names used to describe the form region. It is important to understand the difference between these names and how they affect the form region. The following table describes each name.
| Form region name | Description |
|---|---|
| Form region item name | The name that you specify for the Outlook Form Region item in the Add New Item dialog box. This is the name of the form region code file that appears in Solution Explorer. |
| FormRegionName property | You specify this name in the Supply descriptive text and select your display preferences page of the New Outlook Form Region wizard. This name appears as the FormRegionName property in the Properties window. Use the FormRegionName property to specify the label that identifies the form region in the Outlook user interface (UI). For separate form regions, this name appears as a button on the Ribbon of the Outlook item. For adjoining form regions, this name appears as header text above the form region. |
Microsoft.Office.Tools.Outlook.FormRegionName attribute |
When you add an Outlook Form Region item to the project, Visual Studio sets this property to the fully qualified name of the form region. The default fully qualified name is the name of the VSTO Add-in connected to the name of the form region by a dot—for example, OutlookAddIn1.FormRegion1.This fully qualified name also appears as an attribute at the top of the form region factory class. Use the Microsoft.Office.Tools.Outlook.FormRegionName attribute to uniquely identify the form region across all Outlook VSTO Add-ins. You cannot change the value of the Microsoft.Office.Tools.Outlook.FormRegionName attribute by renaming the form region item or by changing the FormRegionName property. To change this name, you must modify the Microsoft.Office.Tools.Outlook.FormRegionName attribute in the form region code file. |
Disable form region inheritance
By default, a custom message class inherits all the form region associations of the base message class. For example, a message class named IPM.Task.Contoso derives from IPM.Task. Therefore, IPM.Task.Contoso inherits the form region associations of IPM.Task.
If you do not want the form region to be associated with any derived message classes, set the ExactMessageClass property of the form region to true. For example, if you associate an adjoining form region with IPM.Task and set the ExactMessageClass property to true, the form region will only be appended to the bottom of a standard task form. The form region will not be appended to the bottom of any customized versions of a standard task form.
Understand types and message class names
The type name of an Outlook item differs from the message class name of an Outlook item. For example, the type name of an RSS item is Microsoft.Office.Interop.Outlook.PostItem. The message class name of an RSS item is IPM.Post.RSS.
Use the type name to reference an Outlook item in code. For a list of type names, see Associate a form region with an Outlook message class.
Use the message class name of Outlook items in the New Outlook Form Region wizard to associate the item with the form region. For a list of valid message class names, see Associate a form region with an Outlook message class.
Design adjoining form regions for the Reading Pane
You can use the Outlook Reading Pane to preview an Outlook item without opening the item. The Reading Pane is designed for reading only. Therefore, input controls that you add to an adjoining form region, such as a text box, might not behave as expected when the item and form region are open in the Reading Pane.
For example, if an item that has an adjoining form region is open in the Reading Pane, the following situation is possible:
Select some text in a textbox that is on the form region.
Press Delete.
The entire mail item is deleted instead of the text in the textbox.
If you are designing an adjoining form region that contains input controls, test the controls in the Reading Pane to ensure they work properly. Consider adding custom code that disables controls that do not behave as expected.
Alternatively, you can set the ShowInspectorRead property of the form region to False. This way the form region cannot be used in the Reading Pane.
Use optimal icon sizes
You can specify which icons you want the form region to display by setting icon properties in the Icons property group of the Properties window. Use the following guidelines to achieve the best visual quality:
For the Page icon, use a Portable Network Graphics (PNG) file.
Window icons should be 32 pixels by 32 pixels.
All other icons should be 16 pixels by 16 pixels.
The Page icon appears on the Ribbon of an Inspector for items that have separate, replacement, or replace-all form regions.
The Window icon appears in the notification area and in the Alt+Tab dialog box for open items that display replacement or replace-all form regions.