Drag/Drop Outlook message to form

I want to be able to drag & drop an email message from Outlook onto my form & then save the message to a specified location & also save any attachments to a specified location. I created a label that will accept drag/drop & have the required event handlers in my code. The problem now is I don't know how to cast the dropped message to an Outlook.MailItem object.

When I drop a message onto the label I get this error:
"Unable to cast object of type 'System.Windows.Forms.DataObject' to type 'Microsoft.Office.Interop.Outlook._MailItem'"

Is there a way to convert the DataObject directly to an MailItem object. Thanks for any help...

This is the code I am trying.

Code:

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Imports Microsoft.Office.Interop


    Private Sub Label1_DragEnter(sender As Object, e As DragEventArgs) Handles Label1.DragEnter

        Dim dataFormat = e.Data.GetFormats(False)(1)
        If dataFormat = "RenPrivateLatestMessages" Then
            e.Effect = DragDropEffects.Copy
        End If

    End Sub

    Private Sub Label1_DragDrop(sender As Object, e As DragEventArgs) Handles Label1.DragDrop

        Try

            If e.Data.GetFormats(False)(1) = "RenPrivateLatestMessages" Then

                Dim oApp As Outlook._Application
                Dim oMsg As Outlook._MailItem

                oApp = New Outlook.Application
                oMsg = CType(e.Data, Outlook._MailItem)  <-- stops here

            End If

        Catch ex As Exception
            'handle error
        End Try

    End Sub

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You can find some helpful information here…

https://learn.microsoft.com/en-us/do...ew=outlook-pia

I don't believe this can be handled natively. You have to build in the feature of accepting an OLE object, instead of the few simple items it can handle. This GitHub repository has some info on doing this https://github.com/yasoonOfficial/outlook-dndprotocol, it is in C# but maybe you can get enough information from the setup to make it work, or just write your Winform app in C#.

Quote:

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Originally Posted by .paul.

You can find some helpful information here…

https://learn.microsoft.com/en-us/do...ew=outlook-pia

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Thanks for the reply, but not really what I'm looking for. I know how to use the MailItem object. I just can't figure out how to cast the dropped object to a MailItem object.

Quote:

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Originally Posted by nbrege

Thanks for the reply, but not really what I'm looking for. I know how to use the MailItem object. I just can't figure out how to cast the dropped object to a MailItem object.

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I don't think you can cast it. While searching, i saw something about creating a new MailItem from an object. Not sure if you can do that with a DataObject

I played around with the Winform (they're using .Net Framework 4.5) project from the GitHub link. It didn't have the OleDataReader that the WPF project did, so I moved that over. In this code it takes the dragged object and retrieves the mail item EntryID and then uses that to grab the mail item from outlook and you can do with it what you normally can.


This is still C#; I've not converted it over to vb.net yet.

Code:

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using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using Outlook = Microsoft.Office.Interop.Outlook;

namespace OutlookDndWinForms
{
    public partial class Form1 : Form
    {
        private LocalDropTarget myDropTarget = null;

        public Form1()
        {
            InitializeComponent();
        }

        public IOleDropTarget GetDropTarget()
        {
            this.myDropTarget = new LocalDropTarget();
            return myDropTarget;
        }

        class LocalDropTarget : IOleDropTarget
        {
            private OleOutlookData _outlookObj;

            public OleOutlookData outlookObj
            {
                get => _outlookObj;
            }

        public void OnDragDrop(System.Windows.DataObject d)
            {
                Trace.WriteLine("OnDragDrop");

                var formats = d.GetFormats();

                foreach (var format in formats)
                    Trace.WriteLine(format);

                System.Windows.DataObject obj = d;
                MemoryStream data = (MemoryStream)obj.GetData("RenPrivateMessages");

                if (data is MemoryStream)
                {

                    OleDataReader reader = new OleDataReader(data);
                    _outlookObj = reader.ReadOutlookData();

                    Trace.WriteLine($"Subject:{_outlookObj.Items[0].Subject}");
                    Trace.WriteLine($"Entry ID:{_outlookObj.Items[0].EntryId}");
                }
            }

            public int OleDragEnter(object pDataObj, int grfKeyState, long pt, ref int pdwEffect)
            {
                Trace.WriteLine("OleDragEnter");
                Marshal.FinalReleaseComObject(pDataObj);
                return 0;
            }

            public int OleDragOver(int grfKeyState, long pt, ref int pdwEffect)
            {
                Trace.WriteLine("OleDragOver");
                return 0;
            }

            public int OleDragLeave()
            {
                Trace.WriteLine("OleDragEnter");
                return 0;
            }

            public int OleDrop(object pDataObj, int grfKeyState, long pt, ref int pdwEffect)
            {
                Trace.WriteLine("OleDrop");
                System.Windows.DataObject data = new System.Windows.DataObject(pDataObj);

                OnDragDrop(data);
                Marshal.FinalReleaseComObject(pDataObj);
                return 0;
            }
        }

        private void button1_Click(object sender, EventArgs e)
        {

            var res = RegisterDragDrop(this.panel1.Handle, GetDropTarget());
            lbInfo.Items.Add("registered");
           
        }

        //Native imports
        [DllImport("ole32.dll", ExactSpelling = true, CharSet = CharSet.Auto)]
        public static extern int RegisterDragDrop(IntPtr hwnd, IOleDropTarget target);

        [ComImport(), Guid("00000122-0000-0000-C000-000000000046"), InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
        public interface IOleDropTarget
        {
            [PreserveSig]
            int OleDragEnter(
                [In, MarshalAs(UnmanagedType.Interface)]
                object pDataObj,
                [In, MarshalAs(UnmanagedType.U4)]
                int grfKeyState,
                [In, MarshalAs(UnmanagedType.U8)]
                long pt,
                [In, Out]
                ref int pdwEffect);

            [PreserveSig]
            int OleDragOver(
                [In, MarshalAs(UnmanagedType.U4)]
                int grfKeyState,
                [In, MarshalAs(UnmanagedType.U8)]
                long pt,
                [In, Out]
                ref int pdwEffect);

            [PreserveSig]
            int OleDragLeave();

            [PreserveSig]
            int OleDrop(
                [In, MarshalAs(UnmanagedType.Interface)]
                object pDataObj,
                [In, MarshalAs(UnmanagedType.U4)]
                int grfKeyState,
                [In, MarshalAs(UnmanagedType.U8)]
                long pt,
                [In, Out]
                ref int pdwEffect);
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void btnFindMail_Click(object sender, EventArgs e)
        {
            OleOutlookData outlookData = myDropTarget.outlookObj;

            lbInfo.Items.Add($"Searching Outlook for Entry-ID: {outlookData.Items[0].EntryId}");

            lbInfo.Items.Add("Getting Outlook reference");

            Outlook.Application oApp = new Outlook.Application();
            var ns = oApp.GetNamespace("MAPI");
            var item = ns.GetItemFromID(outlookData.Items[0].EntryId) as Outlook.MailItem;

            lbInfo.Items.Add(item.SenderName);
            lbInfo.Items.Add(item.SenderEmailAddress);
            lbInfo.Items.Add(item.To);

            //oApp.Quit();
        }
    }
}

---

Here is the VB.NET version:

Code:

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Imports System.Runtime.InteropServices
Imports Outlook = Microsoft.Office.Interop.Outlook
Imports System.Windows
Imports System.IO

Public Class Form1

    Dim myDropTarget As LocalDropTarget = Nothing

    Public Function GetDropTarget() As IOleDropTarget
        Me.myDropTarget = New LocalDropTarget
        Return myDropTarget
    End Function

    Friend Class LocalDropTarget
        Implements IOleDropTarget

        Private _outlookObj As OleOutlookData

        Public ReadOnly Property outlookObj As OleOutlookData
            Get
                Return _outlookObj
            End Get
        End Property

        Public Sub OnDragDrop(d As System.Windows.DataObject)
            Trace.WriteLine("OnDragDrop")

            Dim frmts = d.GetFormats()

            For Each fmt In frmts
                Trace.WriteLine(fmt)
            Next

            Dim obj As System.Windows.DataObject = d
            Dim data = CType(obj.GetData("RenPrivateMessages"), MemoryStream)

            If TypeOf data Is MemoryStream Then

                Dim reader As OleDataReader = New OleDataReader(data)
                _outlookObj = reader.ReadOutlookData()

                Trace.WriteLine($"Subject:{_outlookObj.Items(CInt(0)).Subject}")
                Trace.WriteLine($"Entry ID:{_outlookObj.Items(CInt(0)).EntryId}")
            End If
        End Sub

        Private Function IOleDropTarget_OleDragEnter(pDataObj As Object, grfKeyState As Integer, pt As Long, ByRef pdwEffect As Integer) As Integer Implements IOleDropTarget.OleDragEnter

            Trace.WriteLine("OleDragEnter")
            Marshal.FinalReleaseComObject(pDataObj)
            Return 0
        End Function

        Private Function IOleDropTarget_OleDragOver(grfKeyState As Integer, pt As Long, ByRef pdwEffect As Integer) As Integer Implements IOleDropTarget.OleDragOver

            Trace.WriteLine("OleDragOver")
            Return 0
        End Function

        Private Function IOleDropTarget_OleDragLeave() As Integer Implements IOleDropTarget.OleDragLeave

            Trace.WriteLine("OleDragLeave")
            Return 0
        End Function

        Private Function IOleDropTarget_OleDrop(pDataObj As Object, grfKeyState As Integer, pt As Long, ByRef pdwEffect As Integer) As Integer Implements IOleDropTarget.OleDrop

            Trace.WriteLine("OleDrop")
            Dim data As System.Windows.DataObject = New System.Windows.DataObject(pDataObj)

            Me.OnDragDrop(data)
            Marshal.FinalReleaseComObject(pDataObj)
            Return 0
        End Function
    End Class

    <ComImport(),
    Guid("00000122-0000-0000-C000-000000000046"),
    InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)>
    Public Interface IOleDropTarget

        <PreserveSig()>
        Function OleDragEnter(<[In], MarshalAs(UnmanagedType.Interface)> ByVal pDataObj As Object,
                              <[In], MarshalAs(UnmanagedType.U4)> ByVal grfKeyState As Integer,
                              <[In], MarshalAs(UnmanagedType.U8)> ByVal pt As Long,
                              <[In]> ByRef pdwEffect As Integer) As Integer

        <PreserveSig()>
        Function OleDragOver(<[In], MarshalAs(UnmanagedType.U4)> ByVal grfKeyState As Integer,
                            <[In], MarshalAs(UnmanagedType.U8)> ByVal pt As Long,
                            <[In]> ByRef pdwEffect As Integer) As Integer

        <PreserveSig()>
        Function OleDragLeave() As Integer

        <PreserveSig()>
        Function OleDrop(<[In], MarshalAs(UnmanagedType.Interface)> ByVal pDataObj As Object,
                        <[In], MarshalAs(UnmanagedType.U4)> ByVal grfKeyState As Integer,
                        <[In], MarshalAs(UnmanagedType.U8)> ByVal pt As Long,
                        <[In]> ByRef pdwEffect As Integer) As Integer
    End Interface

    'Native imports
    <DllImport("ole32.dll", ExactSpelling:=True, CharSet:=CharSet.Auto)>
    Private Shared Function RegisterDragDrop(ByVal hwnd As IntPtr, ByVal target As IOleDropTarget) As Integer
    End Function

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

        'registering at load doesn't work, might need a timer or something

        'Dim Res = RegisterDragDrop(Me.Panel1.Handle, GetDropTarget())

        'If Res <> 0 Then
        '    MsgBox("Registering DragDrop was unsuccessful")
        '    Exit Sub
        'End If

        'lbInfo.Items.Add("registered")
    End Sub

    Private Sub btnFindMail_Click(sender As Object, e As EventArgs) Handles btnFindMail.Click

        Dim outlookData As OleOutlookData = myDropTarget.outlookObj
        lbInfo.Items.Add($"Searching Outlook for Entry-ID: {outlookData.Items(0).EntryId}")
        lbInfo.Items.Add("Getting Outlook reference")

        Dim oApp As New Outlook.Application
        Dim oNS As Outlook.NameSpace = oApp.GetNamespace("MAPI")
        Dim mailItem As Outlook.MailItem = oNS.GetItemFromID(outlookData.Items(0).EntryId)

        lbInfo.Items.Add(mailItem.SenderName)
        lbInfo.Items.Add(mailItem.SenderEmailAddress)
        lbInfo.Items.Add(mailItem.To)

    End Sub

    Private Sub btnRegister_Click(sender As Object, e As EventArgs) Handles btnRegister.Click
        Dim Res = RegisterDragDrop(Me.Panel1.Handle, GetDropTarget())

        If Res <> 0 Then
            MsgBox("Registering DragDrop was unsuccessful")
            Exit Sub
        End If

        lbInfo.Items.Add("registered")
    End Sub
End Class

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OleOutlookData

Code:

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Friend Class OleOutlookData
    Public Property StoreId As String
    Public Property FolderId As String
    Public Property Items As OleOutlookItemData()
End Class

Friend Class OleOutlookItemData
    Public Property Subject As String
    Public Property EntryId As String
    Public Property SearchKey As String
    Public Property MessageClass As String
End Class

---

OleDataReader

Code:

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'converted from:
' --------------------------------------------------------------------------
' Licensed under MIT License.
'
' Outlook DnD Data Reader
'
' File    : OleDataReader.cs
' Author  : Tobias Viehweger <[email protected] / @mnkypete>
'
' --------------------------------------------------------------------------
Imports System.IO
Imports System.Text

Friend Class OleDataReader
    Private stream As MemoryStream

    Public Sub New(inStream As MemoryStream)
        stream = inStream
    End Sub

    Public Function ReadOutlookData() As OleOutlookData
        Dim reader As BinaryReader = New BinaryReader(stream)

        '1. First 4 bytes are the length of the FolderId (In bytes)
        ' Note: These are possibly uint? We don't expect it to be that long nevertheless..
        Dim folderIdLength As Integer = reader.ReadInt32()

        '2. Read FolderId
        Dim folderId = reader.ReadBytes(folderIdLength)
        Dim folderIdHex = ByteArrayToString(folderId)

        '3. Next 4 bytes are the StoreId length (In bytes)
        Dim storeIdLength As Integer = reader.ReadInt32()

        '4. Read StoreId
        Dim storeId = reader.ReadBytes(storeIdLength)
        Dim storeIdHex = ByteArrayToString(storeId)

        '5. There are now some bytes which are not identified yet..
        reader.ReadBytes(4)
        reader.ReadBytes(4)
        reader.ReadBytes(4) ' <== These appear to be folder dependent somehow..

        '6. Read items count, again, we assume int instead of uint because that much items
        '  => Other problems =)
        Dim itemCount As Integer = reader.ReadInt32()

        Dim items = New OleOutlookItemData(itemCount - 1) {}

        For i = 0 To itemCount - 1
            'First 4 bytes, represent the MAPI property 0x8014 ("SideEffects" in OlSpy)
            Dim sideEffects As Integer = reader.ReadInt32()

            'Next byte tells us the length of the message class string (i.e. IPM.Note)
            Dim classLength As Byte = reader.ReadByte()

            'Now, read type
            Dim messageClass = Encoding.ASCII.GetString(reader.ReadBytes(classLength))

            'Next, read the unicode char (!) count of the subject
            ' Note: It seems that Outlook limits this to 255, cross reference mail spec sometime..
            Dim subjectLength As Byte = reader.ReadByte()

            'Read the subject, note that this is unicode, so we need to read 2 bytes per char!
            Dim subject = Encoding.Unicode.GetString(reader.ReadBytes(subjectLength * 2))

            'Next up: EntryID including it's length (same as for store + folder)
            Dim entryIdLength As Integer = reader.ReadInt32()
            Dim entryId = reader.ReadBytes(entryIdLength)
            Dim entryIdHex = ByteArrayToString(entryId)

            'Now the SearchKey MAPI property of the item
            Dim searchKeyLength As Integer = reader.ReadInt32()
            Dim searchKey = reader.ReadBytes(searchKeyLength)
            Dim searchKeyHex = ByteArrayToString(searchKey)

            'Some more stuff which is not quite clear, the next 4 bytes seem to be always
            ' => E0 80 E9 5A
            reader.ReadBytes(4)

            'The next 24 byte are some more flags which are not worked out yet, afterwards
            ' the next item begins
            reader.ReadBytes(24)

            items(i) = New OleOutlookItemData With {
                .EntryId = entryIdHex,
                .MessageClass = messageClass,
                .SearchKey = searchKeyHex,
                .Subject = subject
            }
        Next

        Dim data As OleOutlookData = New OleOutlookData()
        data.StoreId = storeIdHex
        data.FolderId = folderIdHex
        data.Items = items

        Return data
    End Function

    Private Function ByteArrayToString(ba As Byte()) As String
        Dim hex As StringBuilder = New StringBuilder(ba.Length * 2)
        For Each b In ba
            hex.AppendFormat("{0:x2}", b)
        Next
        Return hex.ToString()
    End Function
End Class

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Here is the VS2019 project if interested https://1drv.ms/u/s!AkG6_LvJpkR7j6hn...wsshA?e=fxXieL