Tech Journey With Gagan: Send Emails Through SendGrid using DotNet

This tutorial guides you through building an email notification system in ASP.NET Core using SendGrid. We’ll cover user registration, OTP email verification, and templated email functionality with best practices.

Step 1: Setting Up SendGrid

Follow this guide to set up your SendGrid account, obtain the API key, and configure it for email delivery.

Step 2: Email Message Structure

The `EmailMessage` class encapsulates the data required for sending emails:

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 public class EmailMessage { public EmailAddress To { get; set; } public string Subject { get; set; } public IDictionary<string, string> TemplateData { get; set; } public EmailTemplateType EmailTemplateType { get; set; }
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public EmailMessage(string to, string subject, 
                    IDictionary<string, string> templateData, 
                    EmailTemplateType emailTemplateType)
{
    To = new EmailAddress(to);
    Subject = subject;
    TemplateData = templateData;
    EmailTemplateType = emailTemplateType;
}
}

Step 3: Email Settings

The `EmailSettings` class manages configuration values for SendGrid:

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 public class EmailSettings { public const string EmailConfiguration = "EmailConfiguration"; public string ApiKey { get; set; } public string From { get; set; } public string Username { get; set; } }

Step 4: SendGrid Email Service

The `SendGridEmailService` handles email sending using SendGrid’s API:

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 public class SendGridEmailService : ISendGridEmailService { private readonly EmailSettings _emailConfig;
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public SendGridEmailService(EmailSettings emailConfig)
{
    _emailConfig = emailConfig;
}

public async Task Send(EmailMessage emailMessage)
{
    var client = new SendGridClient(_emailConfig.ApiKey);
    var msg = CreateEmailMessage(emailMessage);
    var response = await client.SendEmailAsync(msg);

    if ((int)response.StatusCode >= 400)
    {
        throw new Exception($"Failed to send email. Status code: {response.StatusCode}");
    }
}

private SendGridMessage CreateEmailMessage(EmailMessage message)
{
    var htmlBody = GenerateEmailBody(message.EmailTemplateType, message.TemplateData);
    var from = new EmailAddress(_emailConfig.From, _emailConfig.Username);
    return MailHelper.CreateSingleEmail(from, message.To, message.Subject, null, htmlBody);
}

private string GenerateEmailBody(EmailTemplateType emailTemplate, 
                                 IDictionary<string, string> templateData)
{
    var templateContent = File.ReadAllText($"EmailTemplates/{emailTemplate}.template.html");
    var template = Template.Parse(templateContent);
    var renderedContent = template.Render(Hash.FromDictionary(templateData));
    return renderedContent;
}
}

Step 5: Email Template

Create an HTML email template for OTP delivery:

Code Snippet

 <html> <body> <h3>Welcome to Our Service</h3> <p>Your OTP for registration is: <b>{{ OTP }}</b></p> <p>This OTP is valid for 5 minutes.</p> </body> </html>

Step 6: User Registration Workflow

Implement user registration with OTP email verification:

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 public class RegisterUserHandler : IRequestHandler<RegisterUserCommand, bool> { private readonly ApplicationDbContext _dbContext; private readonly ISendGridEmailService _emailService;
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public RegisterUserHandler(ApplicationDbContext dbContext, 
                           ISendGridEmailService emailService)
{
    _dbContext = dbContext;
    _emailService = emailService;
}

public async Task<bool> Handle(RegisterUserCommand request, 
                               CancellationToken cancellationToken)
{
    var otp = new Random().Next(100000, 999999).ToString();
    var user = new User
    {
        Email = request.Email,
        Password = request.Password,
        OTP = otp,
        OtpExpiry = DateTime.UtcNow.AddMinutes(5)
    };

    _dbContext.Users.Add(user);
    await _dbContext.SaveChangesAsync(cancellationToken);

    var emailMessage = new EmailMessage(
        user.Email,
        "Your OTP for Registration",
        new Dictionary<string, string> { { "OTP", otp } },
        EmailTemplateType.OtpEmail
    );

    await _emailService.Send(emailMessage);
    return true;
}
}

Step 7: Configuring Program.cs

Set up services and middleware in the `Program.cs` file:

Code Snippet

 var builder = WebApplication.CreateBuilder(args);
builder.Services.Configure<EmailSettings>( builder.Configuration.GetSection(EmailSettings.EmailConfiguration));

builder.Services.AddTransient<ISendGridEmailService, SendGridEmailService>(); builder.Services.AddControllers(); builder.Services.AddEndpointsApiExplorer(); builder.Services.AddSwaggerGen();

var app = builder.Build();

if (app.Environment.IsDevelopment()) { app.UseSwagger(); app.UseSwaggerUI(); }

app.UseHttpsRedirection(); app.UseAuthorization(); app.MapControllers(); app.Run();

Copy Code Functionality

Include the following JavaScript in your blog to enable the one-click copy functionality:

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 <script> function copyCode(targetId) { const codeBlock = document.getElementById(targetId); navigator.clipboard.writeText(codeBlock.value).then(() => { alert("Code copied to clipboard!"); }); } </script>

Tech Journey With Gagan

Monday, January 13, 2025

Send Emails Through SendGrid using DotNet

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