Attaching ItemAttachment using SDK

[bynnoh]

Describe the bug

What I'm trying to do:
Forward a message with modifications using the SDK.

The issue I'm facing:
The item attachment in the forwarded message is not being attached properly using the SDK.

I've tried following:

if (attachment is ItemAttachment itemAttachment && itemAttachment.Item is Message message)
{
  return new ItemAttachment
  {
    Name = itemAttachment.Name,
    Item = message
  };
}

await graphClient.Users[mailAddress].Messages[messageId].Attachments.PostAsync(returnedItemAttachment);

Initially, I encountered the error:
"Cannot process input of abstract type 'microsoft.graph.outlookItem'."

After finding #2334 , I applied message.BackingStore.InitializationCompleted = false;.

However, this led to another error:
"Maximum number of headers in one message should be less than or equal to 5."

To resolve this, I cleared both message.InternetMessageHeaders and BackingStore, but this brought back the first error.

Question:
How can I properly add an item attachment?

I also attempted to create a new Message object from the existing Item, but this approach doesn’t seem ideal due to potential deserialization errors when handling nested attachments.

Expected behavior

Message sent with attached item attachment.

How to reproduce

Described above.

SDK Version

5.68.0

Latest version known to work for scenario above?

No response

Known Workarounds

#2334

Debug output

Click to expand log

Microsoft.Graph.Models.ODataErrors.ODataError: Cannot process input of abstract type 'microsoft.graph.outlookItem'
   at
Microsoft.Kiota.Http.HttpClientLibrary.HttpClientRequestAdapter.ThrowIfFailedResponseAsync(HttpResponseMessage response, Dictionary2 errorMapping, Activity activityForAttributes, CancellationToken cancellationToken)
   at Microsoft.Kiota.Http.HttpClientLibrary.HttpClientRequestAdapter.SendAsync[ModelType](RequestInformation requestInfo, ParsableFactory1 factory, Dictionary2 errorMapping, CancellationToken cancellationToken)
   at Microsoft.Kiota.Http.HttpClientLibrary.HttpClientRequestAdapter.SendAsync[ModelType](RequestInformation requestInfo, ParsableFactory1 factory, Dictionary2 errorMapping, CancellationToken cancellationToken)
   at Microsoft.Graph.Users.Item.Messages.Item.Attachments.AttachmentsRequestBuilder.PostAsync(Attachment body, Action1 requestConfiguration, CancellationToken cancellationToken);
ry.HttpClientRequestAdapter.SendAsync[ModelType](RequestInformation requestInfo, ParsableFactory1 factory, Dictionary2 errorMapping, CancellationToken cancellationToken)
   at Microsoft.Graph.Users.Item.Messages.Item.Attachments.AttachmentsRequestBuilder.PostAsync(Attachment body, Action1 requestConfiguration, CancellationToken cancellationToken);

Configuration

No response

Other information

No response

[Venkateshdhth]

If I create both the parent email and the ItemAttachment like below, It works. First I'm calling PrepareMessage and then attaching it to a parent message by calling the PrepareParentMessage. However, I'm facing an issue with the attachments inside the ItemAttachment go missing.

private Message PrepareMessage(Email email, bool isHtml, string inputFolderPath)
{
    var from = _configuration["FromAccount"];
    var subject = email.Subject + "_" + _sessionId;
    var to = _configuration["TestInbox"];

    var message = new Message();
    message.ToRecipients = new List<Recipient> { new Recipient { EmailAddress = new EmailAddress { Address = to }, OdataType = "#microsoft.graph.recipient" } };
    message.From = new Recipient { EmailAddress = new EmailAddress { Address = from }, OdataType = "#microsoft.graph.recipient" };
    message.Subject = subject;
    message.Body = new ItemBody { Content = email.Body, ContentType = isHtml ? BodyType.Html : BodyType.Text, OdataType = "#microsoft.graph.itemBody" };

    if (message.Attachments == null)
        message.Attachments = new List<Attachment>();

    foreach (var attachmentFile in email.Attachments)
    {
        var attachmentPath = Path.Combine(inputFolderPath, "Attachments", attachmentFile);

        var attachment = new FileAttachment
        {
            OdataType = "#microsoft.graph.fileAttachment",
            Name = attachmentFile,
            ContentBytes = File.ReadAllBytes(attachmentPath),
            ContentType = MimeTypeHelper.GetMimeType(attachmentFile),
        };

        message.Attachments.Add(attachment);
    }

    return message;
}

private Message PrepareParentMessage(Email email, Message message)
{
    var parentMessage = new Message
    {
        ToRecipients = message.ToRecipients?.Select(r => new Recipient { EmailAddress = new EmailAddress { Address = r.EmailAddress?.Address }, OdataType = "#microsoft.graph.recipient" }).ToList(),
        From = new Recipient { EmailAddress = new EmailAddress { Address = message.From?.EmailAddress?.Address }, OdataType = "#microsoft.graph.recipient" },
        Subject = message.Subject,
        Attachments = new List<Attachment>
        {
            new ItemAttachment
            {
                Name = PrepareItemAttachmentName(email.Subject), // The subject now is the format of subject_sessionId
                Item = message,
                IsInline = false,
                OdataType = "#microsoft.graph.itemAttachment"
            }
        },
        OdataType = "#microsoft.graph.message"
    };

    return parentMessage;
}

Sending the message as below.

var messagePayload = new Microsoft.Graph.Users.Item.SendMail.SendMailPostRequestBody
{
    Message = message,
    SaveToSentItems = true,
};

await graphClient.Users[configuration["FromAccount"]].SendMail.PostAsync(messagePayload);

[MIchaelMainer]

Can you provide a sanitized capture of the JSON payload from the request. Also, can you provide us with a very recent ClientRequestId and TimeStamp from the response?