Supernatix Supernatix - 1 month ago 28
ASP.NET (C#) Question

Saving attachments using MailKit library ?

I'm trying to learn how to use the MailKit library but I am struggling to retrieve attachments. So far my code will open a mailbox, go through each message and store data such as sender, subject, body, date etc. but I can't deal with attachments.

I have tried to use other peoples solutions found on here, on github and other sites but I still don't understand exactly what they are doing in their code and when I come close to getting a solution working it causes more bugs so I get stressed and delete all the code. I don't mean to seem lazy but I would love if somebody could explain how I can achieve this. I'm basically trying to build a mail client for a web forms app.

Below is my code, so as you can see I'm fairly clueless :)

// Open the Inbox folder
client.Inbox.Open(FolderAccess.ReadOnly, cancel.Token);

//get the full summary information to retrieve all details
var summary = client.Inbox.Fetch(0, -1, MessageSummaryItems.Full, cancel.Token);
foreach (var msg in summary)
{
//this code originally downloaded just the text from the body
var text = msg.Body as BodyPartText;
//but I tried altering it so that it will get attachments here also
var attachments = msg.Body as BodyPartBasic;

if (text == null)
{
var multipart = msg.Body as BodyPartMultipart;

if (multipart != null)
{
text = multipart.BodyParts.OfType<BodyPartText>().FirstOrDefault();
}
}

if (text == null)
continue;

//I hoped this would get the messages where the content dispositon was not null
//and let me do something like save the attachments somewhere but instead it throws exceptions
//about the object reference not set to an instance of the object so it's very wrong
if (attachments.ContentDisposition != null && attachments.ContentDisposition.IsAttachment)
{
//I tried to do the same as I did with the text here and grab the body part....... but no
var attachedpart = client.Inbox.GetBodyPart(msg.Index, attachments, cancel.Token);
}

else
{
//there is no plan b :(
}

// this will download *just* the text
var part = client.Inbox.GetBodyPart(msg.Index, text, cancel.Token);
//cast main body text to Text Part
TextPart _body = (TextPart)part;

Answer

I'm not entirely clear on what you want to accomplish, but if you just want to download the message attachments (without downloading the entire message) and save those attachments to the file system, here's how you can accomplish that:

var messages = client.Inbox.Fetch (0, -1, MessageSummaryItems.Full | MessageSummaryItems.UniqueId);
int unnamed = 0;

foreach (var message in messages) {
    var multipart = message.Body as BodyPartMultipart;
    var basic = message.Body as BodyPartBasic;

    if (multipart != null) {
        foreach (var attachment in multipart.BodyParts.OfType<BodyPartBasic> ().Where (x => x.IsAttachment)) {
            var mime = (MimePart) client.Inbox.GetBodyPart (message.UniqueId.Value, attachment);
            var fileName = mime.FileName;

            if (string.IsNullOrEmpty (fileName))
                fileName = string.Format ("unnamed-{0}", ++unnamed);

            using (var stream = File.Create (fileName))
                mime.ContentObject.DecodeTo (stream);
        }
    } else if (basic != null && basic.IsAttachment) {
        var mime = (MimePart) client.Inbox.GetBodyPart (message.UniqueId.Value, basic);
        var fileName = mime.FileName;

        if (string.IsNullOrEmpty (fileName))
            fileName = string.Format ("unnamed-{0}", ++unnamed);

        using (var stream = File.Create (fileName))
            mime.ContentObject.DecodeTo (stream);
    }
}