Iterate through a list of email addresses and send email microsoft graph c#

Question

I am iterating through a data table of email addresses and sending an email using microsoft.graph and azure.identity. My code is working, but I don't think it is efficient. My issues are the following

• how do I know when the emails are finished sending - it just stays on the "Send Email" window
• I want emails to continue sending even if one or more in the list are in error (Do I just remove the try / catch?)

Please take a look at my code and make recommendations. I am not too familiar with the environment.

using System;

using System.Collections.Generic;

using System.Data;

using System.Threading.Tasks;

using System.Windows.Forms;

using IBM.Data.DB2.iSeries;

using Microsoft.Graph;

using Microsoft.Graph.Models;

using Azure.Identity;

using System.Configuration;

using Microsoft.Graph.Users.Item.SendMail;

namespace HK_Emailer

{

public partial class Form1 : Form

{

    DataTable dtEmail = new DataTable();

   string htmlBody = "";

    public Form1()

    {

        InitializeComponent();

    }

        public async void btnSend_Click(object sender, EventArgs e)

    {

        try

        {

            string un = ConfigurationManager.AppSettings["ALUsername"];

            string pw = ConfigurationManager.AppSettings["ALPwd"];

            iDB2Connection conn = new iDB2Connection("DataSource=xxx.xxx.xx.xx;UserID=" + un + ";Password=" + pw + ";DataCompression=True;");

            conn.Open();

            iDB2Command MyDB2Command = conn.CreateCommand();

            //SQL query to get email addresses

           MyDB2Command.CommandText = "select xxx as Email from xxx; "                        

            iDB2DataAdapter adapter = new iDB2DataAdapter();

            adapter.SelectCommand = MyDB2Command;

            dtEmail.Clear();

            adapter.Fill(dtEmail);

            adapter.Dispose();

            MyDB2Command.Dispose();

            conn.Close();

             await SendEmail("mailer@humkoop.co.za", dtEmail);

        }

        catch (Exception ex)

        {

            MessageBox.Show(ex.ToString());

        }

    }


      

    static async Task SendEmail(string fromAddress, DataTable dtEmail)

    {

        var scopes = new[] { "https://graph.microsoft.com/.default" };

        var tenantId = ConfigurationManager.AppSettings["tenantId"];

        var clientId = ConfigurationManager.AppSettings["clientId"];

        var clientSecret = ConfigurationManager.AppSettings["clientSecret"];

        var options = new TokenCredentialOptions

        {

            AuthorityHost = AzureAuthorityHosts.AzurePublicCloud

        };

       var clientSecretCredential = new ClientSecretCredential(tenantId, clientId, clientSecret, options);

       var graphClient = new GraphServiceClient(clientSecretCredential, scopes);

       string Subject = "Notice";

       var htmlBody = System.IO.File.ReadAllText("Path of HTML for email");

        // Attachment 1

        var file1 = "path of attachment";

        byte[] fileArray1 = System.IO.File.ReadAllBytes(@file1);


       


   

        foreach (DataRow row in dtEmail.Rows)

        {

            string AddressTrim = row["Email"].ToString().Replace(" ", string.Empty);

            var requestBody = new SendMailPostRequestBody

            {

                Message = new Microsoft.Graph.Models.Message

                {

                    Subject = Subject,

                    Body = new ItemBody

                    {

                        ContentType = BodyType.Html,

                        Content = htmlBody,

                    },

                    ToRecipients = new List