Microsoft Graph，向电子邮件添加多个附件

Question

我正在使用 .netCore 和 Microsoft Graph 并尝试将多个附件添加到电子邮件中并发送。电子邮件发送得很好，一切都在那里（如果我发送 2 个附件，您会看到有 2 个附件），但是收件人只能打开第一个附件。（所有附件都小于 4MB 最大值，所以这不是问题）。

密码是

string content = "{\"message\":{" +
                              "\"subject\":\"" + email.Subject + "\"," +
                               "\"body\":{" +
                                     "\"contentType\": \"HTML\"," +
                                     "\"content\": \"" + email.Msg + "\"" +
                            "}," +
                             "\"toRecipients\": [";
        foreach (var adr in email.SendTo)
        {
            content += "{\"emailAddress\": {\"address\": \"" + adr + "\"} },";
        }
        content += "]";
        if ( email.file != null ) // this is an collection of IFormFile 
        {
            List<EmailAttachment> emailAttachment = new List<EmailAttachment>();
            using (var memoryStream = new MemoryStream())
            {
                foreach (var elem in email.file)
                {
                    await elem.CopyToAsync(memoryStream);
                    emailAttachment.Add(new EmailAttachment
                    {
                        FileName = elem.FileName,
                        AttachmentFile = Convert.ToBase64String(memoryStream.ToArray()),
                        ContentType = elem.ContentType
                    });
                }
            }
            content += ", \"attachments\": [";  //, \"hasAttachments\": true
            emailAttachment.ForEach(elem =>
            {
                content += "{\"@odata.type\": \"#microsoft.graph.fileAttachment\"," +
                            "\"name\":\" " + elem.FileName + "\"," +
                            "\"contentType\":\" " + elem.ContentType +" \"," +
                            "\"contentBytes\":\" " + elem.AttachmentFile + "\"},";
            });
            content += "]";
        }
        content += " }}";

        StringContent contentString = new StringContent(content, Encoding.UTF8, "application/json");

我代码的下一步是将此 httpContent 发送到 Microsoft Graph。

但是，问题是，如您所见，我尝试制作一组要发送的附件，但电子邮件的收件人只能打开一个附件（他确实看到了所有 3 个附件）。（注意：我制作了一组收件人以立即发送并且效果很好）。

感谢您的宝贵时间！

Answer 1

几个小时后，答案是我将一个内存流用于多个附件。它一定是弄混了，不起作用。我现在将 foreach 移到了内存流之外，一切正常。每个附件一个内存流。

Microsoft Graph，向电子邮件添加多个附件

Microsoft Graph, adding multiple attachments to an email

c#

msal

asp.net-core-2.0

microsoft-graph-api