Send-Email-CSharp/ConsoleApp1/MailService.cs

using System.Net;
using System.Net.Mail;

namespace ConsoleApp1;

public class MailService
{
    private readonly SmtpSettings _smtpSettings;

    public MailService(SmtpSettings smtpSettings)
    {
        _smtpSettings = smtpSettings;
    }

    public void SendEmail(string to, string subject, string body)
    {
        using (var client = new SmtpClient(_smtpSettings.SmtpServer, _smtpSettings.SmtpPort))
        {
            client.Credentials = new NetworkCredential(_smtpSettings.SmtpUser, _smtpSettings.SmtpPassword);
            client.EnableSsl = true;

            var mailMessage = new MailMessage
            {
                From = new MailAddress(_smtpSettings.SmtpFrom),
                Subject = subject,
                Body = body,
                IsBodyHtml = true,
            };

            mailMessage.To.Add(to);

            client.Send(mailMessage);
        }
    }
    
    private void SendEmailHtml(string to, string subject, string body)
    {
        using var client = new SmtpClient(_smtpSettings.SmtpServer, _smtpSettings.SmtpPort);
        client.Credentials = new NetworkCredential(_smtpSettings.SmtpUser, _smtpSettings.SmtpPassword);
        client.EnableSsl = true;

        var mailMessage = new MailMessage
        {
            From = new MailAddress(_smtpSettings.SmtpFrom),
            Subject = subject,
            Body = body,
            IsBodyHtml = true,
        };

        mailMessage.To.Add(to);

        client.Send(mailMessage);
    }
    
    public void SendEmailHtmlFile(string to, string subject, string filePath, Dictionary<string, string>? replacements = null)
    {
        string body = System.IO.File.ReadAllText(filePath);
        
        if (replacements is not null)
        {
            foreach (var replacement in replacements)
            {
                body = body.Replace($"{{{replacement.Key}}}", replacement.Value);
            }
        }

        SendEmailHtml(to, subject, body);
    }
  
}