Sending email using C# and the Mailgun API

                            

                                {rn    u0022Loggingu0022: {rn        u0022LogLevelu0022: {rn            u0022Defaultu0022: u0022Informationu0022,rn            u0022Microsoft.AspNetCoreu0022: u0022Warningu0022rn        }rn    },rn    u0022AllowedHostsu0022: u0022*u0022,rn    u0022Mailgunu0022: {rn        u0022ApiKeyu0022: u0022u003cYour API Keyu003eu0022,rn        u0022Domainu0022: u0022u003cYour sandbox domainu003eu0022rn    }rn}
                            
                        

                            

                                using System.Net.Http.Headers;rnusing System.Text;rnrnvar builder = WebApplication.CreateBuilder(args);rnrn// Add services to the containerrnbuilder.Services.AddControllersWithViews();rnrn// Set up your named HttpClient for easy reusernbuilder.Services.AddHttpClient(u0022Mailgunu0022, client =u003ern{rn    // Grab values from the configurationrn    var apiKey = builder.Configuration.GetValueu003cstringu003e(u0022Mailgun:ApiKeyu0022);rn    var base64Auth = Convert.ToBase64String(Encoding.ASCII.GetBytes($u0022api:{apiKey}u0022));rn    var domain = builder.Configuration.GetValueu003cstringu003e(u0022Mailgun:Domainu0022);rnrn    // Set default values on the HttpClientrn    client.BaseAddress = new Uri($u0022https://api.mailgun.net/v3/{domain}/messagesu0022);rn    client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue(u0022Basicu0022, base64Auth);rn});rnrnvar app = builder.Build();rn
                            
                        

                            

                                using System.Diagnostics;rnusing Microsoft.AspNetCore.Mvc;rnusing MailDemo.Models;rnusing System.Text;rnusing System.Net.Mime;rnrnnamespace MailDemo.Controllers;rnrnpublic class OrderController : Controllerrn{rn    private readonly HttpClient _httpClient;rn    private readonly IConfiguration _config;rnrn    public OrderController(IHttpClientFactory httpClientFactory, IConfiguration config)rn    {rn        // Get your named HttpClient that is preconfiguredrn        this._httpClient = httpClientFactory.CreateClient(u0022Mailgunu0022);rn        this._config = config;rn    }rnrn    public async Tasku003cIActionResultu003e Confirm()rn    {rn        using MultipartFormDataContent form = new();rnrn        // Local function keeps this code a bit clearerrn        void SetFormParam(string key, string value) =u003ern        form.Add(new StringContent(value, Encoding.UTF8, MediaTypeNames.Text.Plain), key);rnrn        SetFormParam(u0022fromu0022, $u0022Test User u003cpostmaster@{this._config.GetValueu003cstringu003e(u0022Mailgun:Domainu0022)}u003eu0022);rn        SetFormParam(u0022tou0022, u0022your_authorized_recipient.comu0022);rn        SetFormParam(u0022subjectu0022, u0022Hello World!u0022);rn        SetFormParam(u0022textu0022, u0022My first transactional email!u0022);rn        SetFormParam(u0022htmlu0022, @u0022u003chtmlu003eu003cbodyu003eu003cp style=u0022u0022color:blue;u0022u0022u003eMy first transactional email!u003c/pu003eu003c/bodyu003eu003c/htmlu003eu0022);rnrn        var result = await this._httpClient.PostAsync(string.Empty, form);rnrn        if (!result.IsSuccessStatusCode)rn        {rn            return new JsonResult(await result.Content.ReadAsStringAsync());rn        }rnrn        return new JsonResult(@u0022Your order was confirmed. You should get an email soon!u0022);rn    }rn}rn
                            
                        

                            

                                if (!result.IsSuccessStatusCode)rn{rn    var status = (int) result.StatusCode;rnrn    if (status == 400)rn    {rn        var responseContent = await result.Content.ReadAsStringAsync();rn        var exception = new BadHttpRequestException(u0022Mailgun 400 HTTP status codeu0022);rnrn        this._logger.LogError(exception, exception.Message, responseContent);rn        throw exception;rn    }rn}rn
                            
                        

                            

                                if (!result.IsSuccessStatusCode)rn{rn    var status = (int) result.StatusCode;rnrn    if (status == 500)rn    {rn        // Retry the email after 1 second in hopes that the error was transientrnrn        await Task.Delay(1000);rn        result = await _httpClient.PostAsync(string.Empty, form);rnrn        if (!result.IsSuccessStatusCode)rn        {rn            // Log and throw an exception like you did in the previous examplern        }rn    }rn}rn
                            
                        

                            

                                if (!result.IsSuccessStatusCode)rn{rn    var status = (int)result.StatusCode;rnrn    if (status == 400)rn    {rn        // Log the error and notify the development team that thern        // request was not formatted properly.rn    }rn    else if (status == 401)rn    {rn        // Log the error and notify the development team that thern        // request's authentication failed.rn    }rn    else if (status == 429)rn    {rn        // Use a .NET library like Polly to throttle or try this requestrn        // again with an exponential back-off, etc.rn    }rn    elsern    {rn        // Something went wrong: log the error and apply a distributed rn        // error handling technique like a circuit breaker.rn        // See https://learn.microsoft.com/en-us/azure/architecture/patterns/circuit-breaker for more.rn    }rn}rn
                            
                        

                            

                                u0022Coravelu0022: {rn    u0022Mailu0022: {rn        u0022Fromu0022: {rn            u0022Nameu0022: u0022Test Useru0022,rn            u0022Emailu0022: u0022postmaster@u003cYour sandbox domainu003eu0022rn        }rn    }rn}rnNext, create a class file called MailgunMailer.cs that implements the ICanSendMail interface. You might notice that this is essentially the same logic you originally had in OrderController:rnusing System.Net.Mime;rnusing System.Text;rnusing Coravel.Mailer.Mail;rnrnnamespace MailDemo;rnrnpublic class MailgunMailer : ICanSendMailrn{rn    private readonly HttpClient _httpClient;rn    private readonly IConfiguration _config;rnrn    public MailgunMailer(IHttpClientFactory httpClientFactory, IConfiguration config)rn    {rn        this._httpClient = httpClientFactory.CreateClient(u0022Mailgunu0022);rn        this._config = config;rn    }rnrn    public async Task SendAsync(MessageBody message, string subject, IEnumerableu003cMailRecipientu003e to, MailRecipient from, MailRecipient replyTo, IEnumerableu003cMailRecipientu003e cc, IEnumerableu003cMailRecipientu003e bcc, IEnumerableu003cAttachmentu003e? attachments = null, MailRecipient? sender = null)rn    {rn        using MultipartFormDataContent form = new();rnrn        void SetFormParam(string key, string value) =u003ern        form.Add(new StringContent(value, Encoding.UTF8, MediaTypeNames.Text.Plain), key);rnrn        if (from is not null)rn        {rn            SetFormParam(u0022fromu0022, $u0022{from.Name} u003c{from.Email}u003eu0022);rn        }rn        elsern        {rn            // This gives you a default u0022fromu0022 field if not defined by the callerrn            SetFormParam(u0022fromu0022, $u0022{this._config.GetValueu003cstringu003e(u0022Coravel:Mail:From:Nameu0022)} u003c{this._config.GetValueu003cstringu003e(u0022Coravel:Mail:From:Emailu0022)}u003eu0022);rn        }rnrn        foreach (var recipient in to)rn        {rn            SetFormParam(u0022tou0022, recipient.Email);rn        }rn        SetFormParam(u0022subjectu0022, subject);rnrn        if (message.HasHtmlMessage())rn        {rn            SetFormParam(u0022htmlu0022, message.Html);rn        }rnrn        if (message.HasPlainTextMessage())rn        {rn            SetFormParam(u0022textu0022, message.Text);rn        }rnrn        var result = await _httpClient.PostAsync(string.Empty, form);rnrn        // Error handling logic...rn    }rn}rn
                            
                        

                            

                                builder.Services.AddScopedu003cMailDemo.MailgunMaileru003e();rnbuilder.AddCustomMaileru003cMailDemo.MailgunMaileru003e();rnFinally, replace the code for OrderController with the following:rnusing Microsoft.AspNetCore.Mvc;rnusing Coravel.Mailer.Mail.Interfaces;rnusing Coravel.Mailer.Mail;rnrnnamespace MailDemo.Controllers;rnrnpublic class OrderController : Controllerrn{rn    private readonly IMailer _mailer;rnrn    public OrderController(IMailer mailer)rn    {rn        this._mailer = mailer;rn    }rnrn    public async Tasku003cIActionResultu003e Confirm()rn    {rn        var mailable = Mailable.AsInline()rn            .To(u0022jamesmichaelhickey@gmail.comu0022)rn            .Subject(u0022Hello World!u0022)rn            .Html(@u0022u003chtmlu003eu003cbodyu003eu003cp style=u0022u0022color:blue;u0022u0022u003eMy first transactional email!u003c/pu003eu003c/bodyu003eu003c/htmlu003eu0022)rn            .Text(u0022My first transactional email!u0022);rnrn        await _mailer.SendAsync(mailable);rnrn        return new JsonResult(@u0022Your order was confirmed. You should get an email soon!u0022);rn    }rn}rn