c# - 以编程方式从 Outlook 电子邮件中删除附件

我想从 Outlook 中的邮件中删除所有附件。不知道，我做错了什么。代码不会导致异常，但删除后附件仍然可用。这是我的代码：

如果它正在运行或正在运行 Outlook，如果它没有运行，这会给我一个 Outlook.application 对象：

    public static OL.Application GetOutlook(out bool StillRunning)
    {
        OL.Application OLApp = null;

        if (System.Diagnostics.Process.GetProcessesByName("OUTLOOK").Count() > 0)
        {
            StillRunning = true;
            return System.Runtime.InteropServices.Marshal.GetActiveObject("Outlook.Application") as Microsoft.Office.Interop.Outlook.Application;
        }
        else
        {
            StillRunning = false;
            OLApp = new OL.Application();
            OL.NameSpace nameSpace = OLApp.GetNamespace("MAPI");
            nameSpace.Logon("", "", System.Reflection.Missing.Value, System.Reflection.Missing.Value);
            nameSpace = null;
            return OLApp;
        }
    }

此函数通过其 EntryID 返回邮件：

public static OL.MailItem GetMailByEntryId(OL.Application OlApp, string MailItemEntryID)
    {
        OL.NameSpace olNS = null;
        object obj = null;
        olNS = OlApp.GetNamespace("MAPI");
        if (olNS == null) { throw new System.Exception("ERROR: Unable to get Namespace 'MAPI' in Outlook.Application object!"); }

        OL.MailItem MI = null;
        obj = olNS.GetItemFromID(MailItemEntryID);
        if (obj != null && obj is OL.MailItem) { MI = obj as OL.MailItem; }
        if (MI == null) { throw new System.Exception("ERROR: Unable to get mail item by ID " + System.Environment.NewLine + MailItemEntryID); }

        return MI;
    }

在这里，我尝试删除邮件的附件：

    public static void RemoveAttachments(string EntryID)
    {
        bool StillRunning = false;
        OL.Application OLApp = GetOutlook(out StillRunning);

        OL.MailItem MI = GetMailByEntryId(OLApp, EntryID);

        for(int i = 0; i < MI.Attachments.Count; i++) { MI.Attachments.Remove(i); } //Methode Delete() not available...

        MI.Save();

        if (!StillRunning) { OLApp.Quit(); OLApp = null; System.GC.Collect(); KillOutlook(); }
    }

谢谢大家的帮助...