Managing Outlook Items as Conversations
In Microsoft Outlook, a conversation groups messages that share the same subject and belong to the same thread. In the Outlook user interface, you can expand a conversation in Conversation view to provide a visual relationship between messages, including any responses and related messages from other folders. A conversation can also include branches, such as when a message gets two or more responses and discussions grow independently from each. Since Microsoft Outlook 2010, Conversation view relates all items in the same conversation across folders and stores.
From the programmatic perspective, items in the same conversation can be heterogeneous, belonging to one or more item types. For example, a conversation can contain MailItem and TaskItem objects. Before Outlook 2010, support for items that belong to the same conversation was limited to the ConversationIndex and ConversationTopic properties (for all item types except the NoteItem object). Clearing the ConversationIndex was limited to the MailItem, PostItem, and SharingItem objects. Since Outlook 2010, Outlook supports the Conversation object, which relates all items in the same conversation across folders and across stores by using the ConversationID property on the Conversation object as well as on each item of the conversation. Outlook provides a GetConversation method for most item types to enable you to obtain a Conversation object based on the item.
Conversation view is supported by stores that are POP, IMAP, PST, or Microsoft Exchange Server (at least Microsoft Exchange Server 2010, or Microsoft Exchange Server 2007 if Outlook is running in cached mode). You can call the IsConversationEnabled property of the Store object to verify whether the store supports Conversation view. You can call the GetConversation method to get a Conversation object based on an item in the conversation only if the store in which the item resides supports Conversation view.
To navigate a conversation hierarchy, you can call the GetChildren, GetParent, and GetRootItems methods of the Conversation object. The SimpleItems collection exists to provide easy access to items of the conversation. The order of items in the SimpleItems collection is the same as the order of items in the conversation. The collection is ordered by the MAPI PidTagCreationTime property of each item in ascending order.
To enumerate items in a conversation, you can use the Table object. The rows of the table represent items of the conversation, and the columns of the table, which you can customize, represent properties for each item. To obtain conversation items by using a Table object, use the following procedure:
Obtain the object of any item in the conversation.
To verify that the store supports Conversation view, use the IsConversationEnabled property of the Store object that represents the store in which the item resides. You can obtain a Conversation object based on an item only if the item resides in a store that supports Conversation view.
If the store supports Conversation view, call the GetConversation method of that item to get the Conversation object.
Call the GetTable method of that Conversation object to get a Table.
You can now use methods that the Table object supports to enumerate rows that represent conversation items, and use the default columns to access default item properties (or customize columns to access other properties of the items).
You can use the SetAlwaysDelete and SetAlwaysMoveToFolder methods to always move existing conversation items, and future items that arrive in a specific conversation, to the Deleted Items folder or another folder. The moving of items is supported in the specific store where the item resides, unless the store is a non-delivery store such as a PST store. You can use the GetAlwaysDelete and GetAlwaysMoveToFolder methods to get these folders, and the StopAlwaysDelete and StopAlwaysMoveToFolder methods to stop moving existing and future conversation items to such folders.
In addition, you can apply actions to all existing and future items of a conversation.
Call the SetAlwaysAssignCategories and GetAlwaysAssignCategories methods to set and get categories, respectively, for existing and future conversation items.
Call the MarkAsRead and MarkAsUnread methods to mark items as read or unread, respectively.