Added new functionality to create appointments when dragging & dropping emails into the calendar. By default will create them on the designated day, using current's day time rounded up within the following 15 minutes.

Outlook2013TodoAddIn/AppointmentsControl.cs

@@ -11,15 +11,6 @@ namespace Outlook2013TodoAddIn
     /// </summary>
     public partial class AppointmentsControl : UserControl
     {
-        #region "Variables"
-        
-        /// <summary>
-        /// Used to retrieve the email address of a contact
-        /// </summary>
-        private const string PR_SMTP_ADDRESS = "http://schemas.microsoft.com/mapi/proptag/0x39FE001E";
-
-        #endregion "Variables"
-
         #region "Properties"
         
         /// <summary>
@@ -283,10 +274,10 @@ namespace Outlook2013TodoAddIn
                 if (appt != null)
                 {
                     Outlook.MailItem mail = Globals.ThisAddIn.Application.CreateItem(Outlook.OlItemType.olMailItem) as Outlook.MailItem;
-                    string curUserAddress = GetEmailAddress(Globals.ThisAddIn.Application.Session.CurrentUser);
+                    string curUserAddress = OutlookHelper.GetEmailAddress(Globals.ThisAddIn.Application.Session.CurrentUser);
                     foreach (Outlook.Recipient rcpt in appt.Recipients)
                     {
-                        string smtpAddress = GetEmailAddress(rcpt);
+                        string smtpAddress = OutlookHelper.GetEmailAddress(rcpt);
                         if (curUserAddress != smtpAddress)
                         {
                             mail.Recipients.Add(smtpAddress);
@@ -299,17 +290,6 @@ namespace Outlook2013TodoAddIn
             }
         }
 
-        /// <summary>
-        /// Resolves Outlook recipient email address
-        /// </summary>
-        /// <param name="rcpt">Recipient</param>
-        /// <returns>Email address of the contact</returns>
-        private string GetEmailAddress(Outlook.Recipient rcpt)
-        {
-            Outlook.PropertyAccessor pa = rcpt.PropertyAccessor;
-            return pa.GetProperty(PR_SMTP_ADDRESS).ToString();
-        }
-
         /// <summary>
         /// Switch to the calendar view when double-clicking a date
         /// </summary>

Outlook2013TodoAddIn/CustomCalendar.cs

@@ -7,6 +7,7 @@ using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 using System.Windows.Forms;
+using Outlook = Microsoft.Office.Interop.Outlook;
 
 namespace Outlook2013TodoAddIn
 {
@@ -156,6 +157,9 @@ namespace Outlook2013TodoAddIn
                         lblCtrl.MouseLeave += lblCtrl_MouseLeave;
                         lblCtrl.Click += lblCtrl_Click; // TODO: If we disable this, then we can't select a date...
                         lblCtrl.DoubleClick += lblCtrl_DoubleClick;
+                        lblCtrl.AllowDrop = true;
+                        lblCtrl.DragEnter += lblCtrl_DragEnter;
+                        lblCtrl.DragDrop += lblCtrl_DragDrop;
                     }
                     this.tableLayoutPanel1.Controls.Add(lblCtrl);
                     this.tableLayoutPanel1.SetCellPosition(lblCtrl, new TableLayoutPanelCellPosition(col, row));
@@ -166,6 +170,92 @@ namespace Outlook2013TodoAddIn
             this.btnNext.FlatAppearance.MouseOverBackColor = this.HoverBackColor;
         }
 
+        /// <summary>
+        /// To enable/disable drop operations on every day of the calendar
+        /// </summary>
+        /// <param name="sender">Sender</param>
+        /// <param name="e">DragEventArgs</param>
+        private void lblCtrl_DragEnter(object sender, DragEventArgs e)
+        {
+            List<string> outlookRequiredFormats = new List<string>() { "RenPrivateSourceFolder", "RenPrivateMessages", "RenPrivateItem", "FileGroupDescriptor", "FileGroupDescriptorW", "FileContents", "Object Descriptor" };
+            if (outlookRequiredFormats.All(r => e.Data.GetDataPresent(r)))
+            {
+                e.Effect = DragDropEffects.Copy;
+            }
+            else
+            {
+                e.Effect = DragDropEffects.None;
+            }
+        }
+
+        /// <summary>
+        /// When the user "drops" one or more email items into the calendar
+        /// </summary>
+        /// <param name="sender">Sender</param>
+        /// <param name="e">DragEventArgs</param>
+        private void lblCtrl_DragDrop(object sender, DragEventArgs e)
+        {
+            Label lblDay = sender as Label;
+            if (sender != null)
+            {
+                Outlook.Explorer mailExpl = Globals.ThisAddIn.Application.ActiveExplorer();
+                List<string> attendees = new List<string>();
+                string curUserAddress = OutlookHelper.GetEmailAddress(Globals.ThisAddIn.Application.Session.CurrentUser);
+                string body = String.Empty;
+                string subject = String.Empty;
+                foreach (object obj in mailExpl.Selection)
+                {
+                    Outlook.MailItem mail = obj as Outlook.MailItem;
+                    if (mail != null)
+                    {
+                        subject = mail.Subject;
+                        body = mail.Body;
+                        if (mail.SenderEmailAddress != curUserAddress && !attendees.Contains(mail.SenderEmailAddress))
+                        {
+                            attendees.Add(mail.SenderEmailAddress);
+                        }
+                        attendees.AddRange(OutlookHelper.GetRecipentsEmailAddresses(mail.Recipients, curUserAddress));
+                    }
+                    else // It's not an email, let's see if it's a meeting instead
+                    {
+                        Outlook.MeetingItem meeting = obj as Outlook.MeetingItem;
+                        if (meeting != null)
+                        {
+                            subject = meeting.Subject;
+                            body = meeting.Body;
+                            if (meeting.SenderEmailAddress != curUserAddress && !attendees.Contains(meeting.SenderEmailAddress))
+                            {
+                                attendees.Add(meeting.SenderEmailAddress);
+                            }
+                            attendees.AddRange(OutlookHelper.GetRecipentsEmailAddresses(meeting.Recipients, curUserAddress));
+                        }
+                        else // It wasn't a meeting either, let's try with an appointment
+                        {
+                            Outlook.AppointmentItem appointment = obj as Outlook.AppointmentItem;
+                            if (appointment != null)
+                            {
+                                subject = appointment.Subject;
+                                body = appointment.Body;
+                                if (appointment.Organizer != curUserAddress && !attendees.Contains(appointment.Organizer))
+                                {
+                                    attendees.Add(appointment.Organizer);
+                                }
+                                attendees.AddRange(OutlookHelper.GetRecipentsEmailAddresses(appointment.Recipients, curUserAddress));
+                            }
+                        }
+                    }
+                }
+                Outlook.AppointmentItem appt = Globals.ThisAddIn.Application.CreateItem(Outlook.OlItemType.olAppointmentItem) as Outlook.AppointmentItem;
+                attendees.ForEach(a => appt.Recipients.Add(a));
+                appt.Body = Environment.NewLine + Environment.NewLine + body;
+                appt.Subject = subject;
+                DateTime day = (DateTime)lblDay.Tag;
+                DateTime now = DateTime.Now;
+                appt.Start = OutlookHelper.RoundUp(new DateTime(day.Year, day.Month, day.Day, now.Hour, now.Minute, now.Second), TimeSpan.FromMinutes(15));
+                appt.Display();
+            }
+        }
+
         /// <summary>
         /// Changes labels according to the currently displayed month
         /// </summary>

Outlook2013TodoAddIn/Outlook2013TodoAddIn.csproj

@@ -201,6 +201,7 @@
     <Compile Include="NewMailAlert.Designer.cs">
       <DependentUpon>NewMailAlert.cs</DependentUpon>
     </Compile>
+    <Compile Include="OutlookHelper.cs" />
     <Compile Include="Properties\AssemblyInfo.cs">
       <SubType>Code</SubType>
     </Compile>

Outlook2013TodoAddIn/OutlookHelper.cs

@@ -0,0 +1,67 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using Outlook = Microsoft.Office.Interop.Outlook;
+
+namespace Outlook2013TodoAddIn
+{
+    public class OutlookHelper
+    {
+        #region "Variables"
+
+        /// <summary>
+        /// Used to retrieve the email address of a contact
+        /// </summary>
+        private const string PR_SMTP_ADDRESS = "http://schemas.microsoft.com/mapi/proptag/0x39FE001E";
+
+        #endregion "Variables"
+
+        #region "Methods"
+
+        /// <summary>
+        /// Resolves Outlook recipient email address
+        /// </summary>
+        /// <param name="rcpt">Recipient</param>
+        /// <returns>Email address of the contact</returns>
+        public static string GetEmailAddress(Outlook.Recipient rcpt)
+        {
+            Outlook.PropertyAccessor pa = rcpt.PropertyAccessor;
+            return pa.GetProperty(PR_SMTP_ADDRESS).ToString();
+        }
+
+        /// <summary>
+        /// Gets a list of recipients email addresses, and when exception is present will not be included
+        /// </summary>
+        /// <param name="rcpts">Recipients</param>
+        /// <param name="exception">Email address exception</param>
+        /// <returns>List of emails</returns>
+        public static List<string> GetRecipentsEmailAddresses(Outlook.Recipients rcpts, string exception)
+        {
+            List<string> results = new List<string>();
+            foreach (Outlook.Recipient rcpt in rcpts)
+            {
+                string smtpAddress = OutlookHelper.GetEmailAddress(rcpt);
+                if (smtpAddress != exception && !results.Contains(smtpAddress))
+                {
+                    results.Add(smtpAddress);
+                }
+            }
+            return results;
+        }
+
+        /// <summary>
+        /// Rounds up a datetime to the nearest X interval
+        /// e.g.: RoundUp(new DateTime(2013, 6, 18, 13, 43, 10), TimeSpan.FromMinutes(15)); -> 6/18/2013 1:45:00 PM
+        /// </summary>
+        /// <param name="dt">DateTime</param>
+        /// <param name="d">TimeSpan</param>
+        /// <returns></returns>
+        public static DateTime RoundUp(DateTime dt, TimeSpan d)
+        {
+            return new DateTime(((dt.Ticks + d.Ticks - 1) / d.Ticks) * d.Ticks);
+        }
+
+        #endregion "Methods"
+    }
+}