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How can I add Outlook attachments in C# using Late Binding?

Posted on 2010-09-13
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Last Modified: 2013-12-16
I need to send emails using Outlook, and I have to use late binding because users have various different versions of Outlook from XP through to 2010.  I cannot use MAPI because I have to be able to send HTML emails.

I have got it all working EXCEPT for adding attachments which fails because retrieving the Attachments property always returns null...  Presumably I am looking for the wrong properly or some other failing on my part!

The code so far is shown below, suggestions would be welcomed.

Chris Bray

public static void SendOutlookEmail(string fromAddress, string toAddress, string ccList, string bccList, string subject, string body, string attachmentList)
        {
            object objOutlookApplication;
            object objOutlookItem;
            Type objClassType;

            try
            {

                objClassType = Type.GetTypeFromProgID("Outlook.Application");

                if (objClassType != null)
                {

                    objOutlookApplication = Activator.CreateInstance(objClassType);
                    objOutlookItem = objOutlookApplication.GetType().InvokeMember("CreateItem", BindingFlags.InvokeMethod, null, objOutlookApplication, new object[] { 0 });

                    // Get all To addresses
                    string[] toAddresses;

                    if (toAddress.Length > 0)
                    {
                        toAddresses = toAddress.Split(';');
                        objOutlookItem.GetType().InvokeMember("To", BindingFlags.SetProperty, null, objOutlookItem, toAddresses);
                    }

                    // Get all CC addresses
                    string[] ccAddresses;
                    if (ccList.Length > 0)
                    {
                        ccAddresses = ccList.Split(';');
                        objOutlookItem.GetType().InvokeMember("CC", BindingFlags.SetProperty, null, objOutlookItem, ccAddresses);
                    }

                    // Get all BCC addresses
                    string[] bccAddresses;
                    if (bccList.Length > 0)
                    {
                        bccAddresses = bccList.Split(';');
                        objOutlookItem.GetType().InvokeMember("BCC", BindingFlags.SetProperty, null, objOutlookItem, bccAddresses);
                    }

                    // Subject
                    if (subject.Length > 0)
                    {
                        objOutlookItem.GetType().InvokeMember("Subject", BindingFlags.SetProperty, null, objOutlookItem, new string[] { subject });
                    }

                    // Body
                    if (body.Length > 0)
                    {
                        objOutlookItem.GetType().InvokeMember("HTMLBody", BindingFlags.SetProperty, null, objOutlookItem, new string[] { body });
                    }

                    // Attachments
                    // split out attachmentList
                    if (attachmentList.Length > 0)
                    {
                        object objAttachments = objOutlookItem.GetType().GetProperty("Attachments", BindingFlags.GetProperty); // Always returns null

                        string[] fileAttachments = attachmentList.Split(';');
                        foreach (string attachment in fileAttachments)
                        {
                            objAttachments.GetType().InvokeMember("Add", BindingFlags.InvokeMethod, null, objAttachments, new object[] { attachment, Type.Missing, Type.Missing, Type.Missing }); // Fails due to null objAttachments
                        }
                    }

                    
                    // Display the dialog
                    objOutlookItem.GetType().InvokeMember("Display", BindingFlags.InvokeMethod, null, objOutlookItem, new object[] { true });

                }
            }
            catch (Exception ex)
            {
                throw;
            }
            finally
            { 
                objOutlookApplication = null;
                objOutlookItem = null;
                objClassType = null;            
            }
        }

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Question by:chrisbray
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4 Comments
 
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Expert Comment

by:starlite551
ID: 33669082
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LVL 3

Author Comment

by:chrisbray
ID: 33670020
Hi starlite551:

Why have you sent me that link?  As far as I can tell it has no relevance whatsoever to the question asked - for a start it is talking about wrting add-ins, and secondly it is using early binding when my question relates to late binding!

Chris Bray
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LVL 14

Accepted Solution

by:
frankhelk earned 500 total points
ID: 33670311
Since I'm not really familiar with these Outlook objects, I'm just speculating on a more theoretical level ....

I think this this returns (null) because the email object has not yet got anything attached ?

I've found something you should have a look at:

Search for "GetTypeFromProgID" on that page, you should reach the 4th message form "Mai08" within the second code snippet.

Take a look at that snippet and the way the attachments are added there (precisely: Find the comment "// Anhänge" (german for "Attachments") and the lines below.

Hope it helps.
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LVL 3

Author Comment

by:chrisbray
ID: 33670458
Hi frankhelk,

Thank you for that - bang on the money!  The answer is that you invoke the member Attachments rather than try to access the property.  For those who may find this thread when searching, and in case the link supplied gets broken, the resulting working code is shown below.

Chris Bray

                    // Attachments
                    // split out attachmentList
                    if (attachmentList.Length > 0)
                    {
                        objAttachments = objOutlookItem.GetType().InvokeMember("Attachments", BindingFlags.GetProperty, null , objOutlookItem, new object[] { Missing.Value });

                        fileAttachments = attachmentList.Split(';');
                        foreach (string attachment in fileAttachments)
                        {
                            objAttachments.GetType().InvokeMember("Add", BindingFlags.InvokeMethod, null, objAttachments, new object[] { attachment, Type.Missing, Type.Missing, Type.Missing });
                        }
                    }
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