如何从C＃中的Outlook仅保存Excel附件？

Question

I have to create a program which saves Excel attachments from the mail inbox. At the moment I am saving all attachments from incoming mails via an event handler, but it seems like that the event is not always triggered but rather 3 from 4 mails only. I don't know the reason though.

So I was thinking about looping through the inbox mails, look for mails with specific subject title and save the attached Excel files.

But how can I do that? Other solutions shows only via add in, but I want to use a Windows service for that.

So far my code (this doesn't work every time though, maybe someone knows a reason for that?)

public partial class MyService : ServiceBase
{
        public string AttachPath = @"[mypath to save attachments]";

        public MyService()
        {
            InitializeComponent();
        }

        public void RunAsConsole(string[] args)
        {
            Console.WriteLine("This service is executed as a console application.");
            Console.WriteLine("Application active.");
            OnStart(args);
            Console.WriteLine("Press q to exit.");
            string userInput = Console.ReadLine();

            while (userInput != "q")
            {
                userInput = Console.ReadLine();
            }

            Console.WriteLine("Finished! \nPress any key to exit...");
            Console.ReadLine();
            OnStop();
        }

        protected override void OnStart(string[] args)
        {
            Outlook.NameSpace outlookNameSpace;
            Outlook.MAPIFolder inbox;
            Outlook.Items items;

            Outlook.Application oApp = new Outlook.Application();
            outlookNameSpace = oApp.GetNamespace("MAPI");
            inbox = outlookNameSpace.GetDefaultFolder(Microsoft.Office.Interop.Outlook.OlDefaultFolders.olFolderInbox);

            items = inbox.Items;
            items.ItemAdd +=
                new Outlook.ItemsEvents_ItemAddEventHandler(items_ItemAdd);
        }

        void items_ItemAdd(object Item)
        {
            string filter = "[myFilter]";
            Outlook.MailItem mail = (Outlook.MailItem)Item;

            if (Item != null)
            {
                if (mail.Subject.ToUpper().Contains(filter.ToUpper()))
                {
                    Console.WriteLine(DateTime.Now.ToShortTimeString() + " Mail found!: " + mail.Subject);

                    if (mail.Attachments.Count > 0)
                    {
                        for (int i = 1; i - 1 < mail.Attachments.Count; ++i)
                        {
                            Console.WriteLine($@"Saving {mail.Attachments[i].FileName}");
                            //Console.WriteLine(Path.Combine(AttachPath, mail.Attachments[i].FileName));
                            string filepath = Path.Combine(AttachPath, mail.Attachments[i].FileName);
                            mail.Attachments[i].SaveAsFile(filepath);

                            //if (File.Exists(filepath))
                            //{
                            //    mail.Delete(); //after saving the file delete the mail
                            //}
                        }
                    }
                    else
                    {
                        Console.WriteLine("No attachments found: execute auto reply...");
                        Outlook.MailItem replyMail = mail.Reply();
                        replyMail.HTMLBody = $@"Some answer for reply";
                        replyMail.Send();
                    }

                    Console.WriteLine("Delete mail: " + mail.Subject.ToString());
                    mail.UnRead = false; //mark as read
                    mail.Delete();
                }
            }
        }

        protected override void OnStop()
        {
            //nothing
        }
    }

At the moment, the service can be executed as a console application and a Windows service, so please don't pay too much attention at that point, it's for debugging reasons.

Answer 1

Other Solutions shows only via add in, but I want to use a windows service for that.

Microsoft does not currently recommend, and does not support, Automation of Microsoft Office applications from any unattended, non-interactive client application or component (including ASP, ASP.NET, DCOM, and NT Services), because Office may exhibit unstable behavior and/or deadlock when Office is run in this environment.

If you are building a solution that runs in a server-side context, you should try to use components that have been made safe for unattended execution. Or, you should try to find alternatives that allow at least part of the code to run client-side. If you use an Office application from a server-side solution, the application will lack many of the necessary capabilities to run successfully. Additionally, you will be taking risks with the stability of your overall solution. Read more about that in the Considerations for server-side Automation of Office article.

As a workaround, you may consider using a low-level API on which Outlook is based on - Extended MAPI or just any wrappers around that API such as Redemption.

If you deal with Exchange only, you may consider using Graph API or EWS, see Start using web services in Exchange for more information.

Answer 2

Please refer to Eugene's answer on the architecture side of things. But from the perspective of extracting the emails with a filter, you can try this code.

Instead of getting items = inbox.Items , try finding the emails with a filter query which returns an Outlook.Table Then you can iterate on this table to get the emails.

const string PropTag = "http://schemas.microsoft.com/mapi/proptag/";
var filter = "@SQL=" + "\"" + PropTag
         + "0x0037001E" + "\"" + " ci_phrasematch " + "\'" + strFilter + "\'";

Outlook.Table table = inbox.GetTable(filter, Outlook.OlTableContents.olUserItems);

while (!table.EndOfTable)            
{
        Outlook.Row nextRow = table.GetNextRow();
        try
        {
            Outlook.MailItem mi;
            try
            {
                string entryId = nextRow["EntryID"];
                var item = outlookNameSpace.GetItemFromID(entryId);
                mi = (Outlook.MailItem)item;
            }
            catch (InvalidCastException ex)
            {
                Console.WriteLine("Cannot cast mail item, so skipping. Error: {0}", e);                       
                continue;
            } 
            //Extract the attachments here and archive or reply - put your logic here
        }
        catch (Exception e)
        {   
            Console.WriteLine("An error occurred: '{0}'", e);
        }
 }