Folder IDs 

A folder ID uniquely identifies a folder at the Exchange Online (Microsoft 365) server. In Rebex Graph, folder IDs are represented by GraphFolderId class.

// create Graph client, connect, log in
// ...

// get list of folders in the mailbox
GraphFolderCollection folders = client.GetFolderList();

// display IDs and names of those folders
foreach (GraphFolderInfo folder in folders)
{
    Console.WriteLine("{0}: {1}", folder.Id, folder.Name);
}

Tip: To get a list of subfolders, use GetFolderList() method and specify the GraphFolderId argument.

Tip: Accessing shared mailboxes is possible as well.

Well-known folder IDs 

Well-known folders such as 'Inbox', 'Drafts' or 'Sent Items' are accessible using a set predefined folder IDs. These constant IDs are accessible through static properties of GraphFolderId class:

• GraphFolderId.Root - The root folder.
• GraphFolderId.Inbox - The "Inbox" folder.
• GraphFolderId.Drafts - The "Drafts" folder.
• GraphFolderId.SentItems - The "Sent Items" folder.
• GraphFolderId.Outbox - The "Outbox" folder.
• GraphFolderId.Archive - The "Archive" folder.
• GraphFolderId.DeletedItems - The "Deleted Items" folder.
• GraphFolderId.Deletions - The "Deletions" folder.
• GraphFolderId.JunkEmail - The "Junk E-mail" folder.
• GraphFolderId.Scheduled - The "Scheduled" folder (also known as "Snoozed").
• GraphFolderId.SearchFolders - The "Search Folders" folder (also known as "Finder").

Getting list of subfolders 

To get a list of subfolders, use GetFolderList() method:

// create Graph client instance, connect, log in
// ...

// find the 'Orders' folder (in the root folder)
GraphFolderCollection folders = client.GetFolderList();
GraphFolderInfo folderOrders = folders.Where(s => s.Name == "Orders").First();

// list subfolders of the 'Orders' folder
GraphFolderCollection subfolders = client.GetFolderList(folderOrders.Id);