c#でgraph apiを使ってメールにファイルを添付し、メールを送信するサンプル

// Create the message with attachment.
byte[] contentBytes = System.IO.File.ReadAllBytes("test.xlsx");
string contentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
MessageAttachmentsCollectionPage attachments = new MessageAttachmentsCollectionPage();

attachments.Add(new FileAttachment
{
    ODataType = "#microsoft.graph.fileAttachment",
    ContentBytes = contentBytes,
    ContentType = contentType,
    ContentId = "test",
    Name = "test.xlsx"
});

var message = new Message
{
    Subject = "こちらは件名です",
    Body = new ItemBody
    {
        ContentType = BodyType.Text,
        Content = "こちらは本文です。"
    },
    ToRecipients = new List<Recipient>()
    {
        new Recipient
        {
            EmailAddress = new EmailAddress
            {
                Address = "[e-mail]"
            }
        }
    },
  　Attachments = attachments
};

//await graphClient.Users["[e-mail]"]→アプリケーション認証

//委任認証
await graphClient.Me
    .SendMail(message,true)
    .Request()
    .PostAsync();

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