You can use the FormRegion.IsExpanded property to check if the form region is currently expanded or collapsed. To expand or collapse the form region, you can use the FormRegion.Expanded property. Here's an example of how you can use these properties to expand the form region if it is currently collapsed:
Outlook.FormRegion formRegion = // get a reference to the form region
if (!formRegion.IsExpanded)
{
formRegion.Expanded = true;
}
Note that this will only work if the form region is of type AdjoiningFormRegion, which supports expanding and collapsing. If the form region is of a different type, this property will not be available.