Want to enumerate Outlook folders

Question

I'm looking for some code (C# or VB.NET preferred) to iterate through all folders in an Outlook mailbox and return the names of those folders. I'm not looking to pop up the Outlook folder dialog, but rather to return the folder names in a given mailbox from outside Outlook.

Thanks

Answer 1

This is actually quite easy using VSTO (Visual Studio Tools for Office). First Use VSTO to create an Outlook 2007 add in. Here is some of my experimental code that does this.

   private void RecurseThroughFolders(Outlook.Folder theRootFolder, int depth)
    {
        if ( theRootFolder.DefaultItemType != Outlook.OlItemType.olMailItem ) {
            return;
        }

        Console.WriteLine("{0}", theRootFolder.FolderPath);

        foreach( Object item in theRootFolder.Items ) {
            if (item.GetType() == typeof( Outlook.MailItem )) {
                Outlook.MailItem mi = (Outlook.MailItem)item;
                if (mi.Categories.Length > 0) {
                    WriteLinePrefix(depth);
                    Console.WriteLine("  $ {0}", mi.Categories);
                }
            }
        }

        foreach (Outlook.Folder folder in theRootFolder.Folders) {
            RecurseThroughFolders(folder, depth + 1);
        }
    }

private void ThisAddIn_Startup(object sender, System.EventArgs e)
{
    Outlook.Application olApp = new Outlook.Application();

    Console.WriteLine("Default Profile = {0}", olApp.DefaultProfileName);

    Console.WriteLine("Default Store = {0}", olApp.Session.DefaultStore.DisplayName);

    selectExplorers = this.Application.Explorers;
    selectExplorers.NewExplorer += new Outlook.ExplorersEvents_NewExplorerEventHandler( newExplorer_Event );

    Outlook.Folder theRootFolder  = (Outlook.Folder) olApp.Session.DefaultStore.GetRootFolder();
    RecurseThroughFolders( theRootFolder, 0 );
}

Answer 2

I prefer a more LINQ friendly approach:

private IEnumerable<MAPIFolder> GetAllFolders(Folders folders)
{
    foreach (MAPIFolder f in folders) {
        yield return f;
        foreach (var subfolder in GetAllFolders(f.Folders)) {
            yield return subfolder;
        }
    }
}

Then you can peruse the folders any way like. For example:

private IEnumerable<MailItem> GetAllEmail(NameSpace ns)
{
    foreach (var f in GetAllFolders(ns.Folders)) {
        if (f == DELETE_FOLDER) continue;
        if (f.DefaultItemType == OlItemType.olMailItem) {
            // Party!
        }
    }
}

Answer 3

I'm still quite new to LINQ, so I might have misunderstood part of the answer from Ray (June 5, 2009) - ...

Looking at the LINQ example from Ray, I would ask "does this only give one level of subfolders" for the first part, and maybe something like "how do I know which folders to exclude?" (or maybe "where do I find the correct name for the folder I want to exclude?") for the second part, considering the exclusion of the DELETE_FOLDER in the given answer...