.NET。Mail未在office 365上发送任何经过两步验证的附加文件

我使用这个发送电子邮件没有问题。Net程序,但如果我附加一个文件,它永远不会到达。 在邮件服务器中显示邮件已正确到达,但不包括任何附件。 另一方面,如果使用相同的配置,我使用PoweShell发送带有附件的电子邮件,则附件到达时不会出现问题。 谢谢

using System.Collections.Generic;
using System.IO;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Net.Mime;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApp
{
    public partial class Form1 : Form
    {
        private string clientId = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx";
        private string clientSecret = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx";
        private string tenantId = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx";
        private string to = "[email protected]";
        private string subject = "Test Email";
        private string body = "This is a test email sent from C# Windows Forms using Microsoft Graph API";
        private string token;

        public Form1()
        {
            InitializeComponent();
        }

        private async void SendEmailButton_Click(object sender, EventArgs e)
        {
            try
            {
                token = await GetAccessToken();

                var email = new
                {
                    saveToSentItems = false,
                    message = new
                    {
                        subject = subject,
                        body = new
                        {
                            contentType = "Text",
                            content = body
                        },
                        toRecipients = new[]
                        {
                            new
                            {
                                emailAddress = new
                                {
                                    address = to
                                }
                            }
                        }
                    },
                    attachments = new[]
                    {
                        new
                            {
                                odataType = "#microsoft.graph.fileAttachment",
                                name = "Hello.pdf",
                                contentBytes = Convert.ToBase64String(File.ReadAllBytes(@"c:\temp\Hello.pdf"))
                            }
                    }
                };

                var emailJson = Newtonsoft.Json.JsonConvert.SerializeObject(email);
                await SendEmail(emailJson);
                MessageBox.Show("Email sent successfully.");
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error sending email: " + ex.Message);
            }
        }

        private async Task<string> GetAccessToken()
        {
            using (var client = new HttpClient())
            {
                var authority = $"https://login.microsoftonline.com/{tenantId}";
                var tokenEndpoint = $"{authority}/oauth2/token";

                var content = new FormUrlEncodedContent(new[]
                {
                    new KeyValuePair<string, string>("grant_type", "client_credentials"),
                    new KeyValuePair<string, string>("client_id", clientId),
                    new KeyValuePair<string, string>("client_secret", clientSecret),
                    new KeyValuePair<string, string>("resource", "https://graph.microsoft.com")
                });

                var response = await client.PostAsync(tokenEndpoint, content);
                var responseContent = await response.Content.ReadAsStringAsync();

                if (response.IsSuccessStatusCode)
                {
                    dynamic jsonResponse = Newtonsoft.Json.JsonConvert.DeserializeObject(responseContent);
                    return jsonResponse.access_token;
                }
                else
                {
                    throw new Exception("Failed to obtain access token.");
                }
            }
        }

        private async Task SendEmail(string emailJson)
        {
            using (var client = new HttpClient())
            {
                client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
                client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);

                var uri = "https://graph.microsoft.com/v1.0/users/[email protected]/sendMail";
                var content = new StringContent(emailJson, Encoding.UTF8, "application/json");
                try
                {
                    var response = await client.PostAsync(uri, content);
                    if (!response.IsSuccessStatusCode)
                    {
                        throw new Exception("Failed to send the email.");
                    }
                }
                catch (Exception ex)
                {
                    MessageBox.Show("Error sending email: " + ex.Message);
                }
            }
        }
    }
}````