Difference between Outlook.Folder and Outlok.MAPIFolder

问题

I'm not clear on the difference between the classes Folder and MAPIFolder in the namespace Outlook. When I review the code in the net, some use the first, while others use the other syntax and I can't really determine if:

it's just because of their ignorance (and even less I can tell which group is the right one)
it's some kind of legacy (usage for different versions of Outlook)
it's the very same thing (something I'm fairly sure isn't true but one never knows)
it's an inheritance structure (and what to use when)
it's simply a way to avoid type issues (casting and as-ing)
it's other reason(s) entirely (and if so, which)

Here's the code I'm using for obtaining those two.

Outlook.Folder defaultContactsFolder_1 = 
  this.Application.Session.GetDefaultFolder(
    Outlook.OlDefaultFolders.olFolderContacts) as Outlook.Folder;

Outlook.MAPIFolder defaultContactFolder_2 = 
  this.Application.GetNamespace("MAPI").GetDefaultFolder(
    Outlook.OlDefaultFolders.olFolderContacts);

回答1:

Folder has superseded MAPIFolder which is now deprecated. See related SO post. Folder has additional event hooks as compared to MAPIFolder

Application.Session == Application.GetNamespace("MAPI") - they are interchangeable. See related SO post.

MAPIFolder and GetNamespace() are carry overs from Outlook 2003 and below - they've just been kept for backwards compatibility. There's no way to avoid type casting with VSTO - you will constantly be boxing and unboxing.

来源：https://stackoverflow.com/questions/12347640/difference-between-outlook-folder-and-outlok-mapifolder

标签

outlook

outlook-addin