Open default mail client along with a attachment

Question

Hi I am working on a WPF application (using c#).

I need to have a functionality where users can send files (audio files) as attachments via email. I tried using

Answer 1

I used the following helper class.

class MAPI
{
    public bool AddRecipientTo(string email)
    {
        return AddRecipient(email, HowTo.MAPI_TO);
    }

    public bool AddRecipientCC(string email)
    {
        return AddRecipient(email, HowTo.MAPI_TO);
    }

    public bool AddRecipientBCC(string email)
    {
        return AddRecipient(email, HowTo.MAPI_TO);
    }

    public void AddAttachment(string strAttachmentFileName)
    {
        m_attachments.Add(strAttachmentFileName);
    }

    public int SendMailPopup(string strSubject, string strBody)
    {
        return SendMail(strSubject, strBody, MAPI_LOGON_UI | MAPI_DIALOG);
    }

    public int SendMailDirect(string strSubject, string strBody)
    {
        return SendMail(strSubject, strBody, MAPI_LOGON_UI);
    }


    [DllImport("MAPI32.DLL")]
    static extern int MAPISendMail(IntPtr sess, IntPtr hwnd,
        MapiMessage message, int flg, int rsv);

    int SendMail(string strSubject, string strBody, int how)
    {
        MapiMessage msg = new MapiMessage();
        msg.subject = strSubject;
        msg.noteText = strBody;

        msg.recips = GetRecipients(out msg.recipCount);
        msg.files = GetAttachments(out msg.fileCount);

        m_lastError = MAPISendMail(new IntPtr(0), new IntPtr(0), msg, how,
            0);
        if (m_lastError > 1)
            MessageBox.Show("MAPISendMail failed! " + GetLastError(), 
                "MAPISendMail");

        Cleanup(ref msg);
        return m_lastError;
    }

    bool AddRecipient(string email, HowTo howTo)
    {
        MapiRecipDesc recipient = new MapiRecipDesc();

        recipient.recipClass = (int)howTo;
        recipient.name = email;
        m_recipients.Add(recipient);

        return true;
    }

    IntPtr GetRecipients(out int recipCount)
    {
        recipCount = 0;
        if (m_recipients.Count == 0)
            return IntPtr.Zero;

        int size = Marshal.SizeOf(typeof(MapiRecipDesc));
        IntPtr intPtr = Marshal.AllocHGlobal(m_recipients.Count * size);

        int ptr = (int)intPtr;
        foreach (MapiRecipDesc mapiDesc in m_recipients)
        {
            Marshal.StructureToPtr(mapiDesc, (IntPtr)ptr, false);
            ptr += size;
        }

        recipCount = m_recipients.Count;
        return intPtr;
    }

    IntPtr GetAttachments(out int fileCount)
    {
        fileCount = 0;
        if (m_attachments == null)
            return IntPtr.Zero;

        if ((m_attachments.Count <= 0) || (m_attachments.Count >
            maxAttachments))
            return IntPtr.Zero;

        int size = Marshal.SizeOf(typeof(MapiFileDesc));
        IntPtr intPtr = Marshal.AllocHGlobal(m_attachments.Count * size);

        MapiFileDesc mapiFileDesc = new MapiFileDesc();
        mapiFileDesc.position = -1;
        int ptr = (int)intPtr;

        foreach (string strAttachment in m_attachments)
        {
            mapiFileDesc.name = Path.GetFileName(strAttachment);
            mapiFileDesc.path = strAttachment;
            Marshal.StructureToPtr(mapiFileDesc, (IntPtr)ptr, false);
            ptr += size;
        }

        fileCount = m_attachments.Count;
        return intPtr;
    }

    void Cleanup(ref MapiMessage msg)
    {
        int size = Marshal.SizeOf(typeof(MapiRecipDesc));
        int ptr = 0;

        if (msg.recips != IntPtr.Zero)
        {
            ptr = (int)msg.recips;
            for (int i = 0; i < msg.recipCount; i++)
            {
                Marshal.DestroyStructure((IntPtr)ptr,
                    typeof(MapiRecipDesc));
                ptr += size;
            }
            Marshal.FreeHGlobal(msg.recips);
        }

        if (msg.files != IntPtr.Zero)
        {
            size = Marshal.SizeOf(typeof(MapiFileDesc));

            ptr = (int)msg.files;
            for (int i = 0; i < msg.fileCount; i++)
            {
                Marshal.DestroyStructure((IntPtr)ptr,
                    typeof(MapiFileDesc));
                ptr += size;
            }
            Marshal.FreeHGlobal(msg.files);
        }

        m_recipients.Clear();
        m_attachments.Clear();
        m_lastError = 0;
    }

    public string GetLastError()
    {
        if (m_lastError <= 26)
            return errors[m_lastError];
        return "MAPI error [" + m_lastError.ToString() + "]";
    }

    readonly string[] errors = new string[] {
    "OK [0]", "User abort [1]", "General MAPI failure [2]",
            "MAPI login failure [3]", "Disk full [4]",
            "Insufficient memory [5]", "Access denied [6]",
            "-unknown- [7]", "Too many sessions [8]",
            "Too many files were specified [9]",
            "Too many recipients were specified [10]",
            "A specified attachment was not found [11]",
    "Attachment open failure [12]",
            "Attachment write failure [13]", "Unknown recipient [14]",
            "Bad recipient type [15]", "No messages [16]",
            "Invalid message [17]", "Text too large [18]",
            "Invalid session [19]", "Type not supported [20]",
            "A recipient was specified ambiguously [21]",
            "Message in use [22]", "Network failure [23]",
    "Invalid edit fields [24]", "Invalid recipients [25]",
            "Not supported [26]"
    };


    List m_recipients = new
        List();
    List m_attachments = new List();
    int m_lastError = 0;

    const int MAPI_LOGON_UI = 0x00000001;
    const int MAPI_DIALOG = 0x00000008;
    const int maxAttachments = 20;

    enum HowTo { MAPI_ORIG = 0, MAPI_TO, MAPI_CC, MAPI_BCC };
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public class MapiMessage
{
    public int reserved;
    public string subject;
    public string noteText;
    public string messageType;
    public string dateReceived;
    public string conversationID;
    public int flags;
    public IntPtr originator;
    public int recipCount;
    public IntPtr recips;
    public int fileCount;
    public IntPtr files;
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public class MapiFileDesc
{
    public int reserved;
    public int flags;
    public int position;
    public string path;
    public string name;
    public IntPtr type;
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public class MapiRecipDesc
{
    public int reserved;
    public int recipClass;
    public string name;
    public string address;
    public int eIDSize;
    public IntPtr entryID;
}

Use the MAPI class as below.

MAPI mapi = new MAPI();

mapi.AddAttachment("c:\\temp\\file1.txt");
mapi.AddAttachment("c:\\temp\\file2.txt");
mapi.AddRecipientTo("person1@somewhere.com");
mapi.AddRecipientTo("person2@somewhere.com");
mapi.SendMailPopup("testing", "body text");

// Or if you want try and do a direct send without displaying the 
// mail dialog mapi.SendMailDirect("testing", "body text");

Reference: Code Project