Step by Step Guide to Building a ConvertKit API Integration in C#

Aug 11, 2024 • 8 minute read

Hey there, fellow developer! Ready to dive into the world of email marketing automation with ConvertKit? Let's build a robust API integration using C# that'll make your life easier and your campaigns more powerful. Buckle up, and let's get coding!

Introduction

ConvertKit's API is a powerhouse for managing subscribers, forms, and sequences programmatically. By the end of this guide, you'll have a slick C# integration that'll have you automating tasks like a pro.

Prerequisites

Before we jump in, make sure you've got:

Visual Studio or your favorite C# IDE
.NET Core 3.1 or later
A ConvertKit account with API access

Grab your API key from the ConvertKit dashboard. You'll need it to authenticate your requests.

Setting up the project

Fire up Visual Studio and create a new C# console application. We'll keep it simple for now, but feel free to adapt this to your specific needs later.

Install these NuGet packages:

dotnet add package Newtonsoft.Json
dotnet add package Microsoft.Extensions.Http

Configuring the API client

Let's set up our HttpClient to talk to ConvertKit:

using System.Net.Http;
using System.Net.Http.Headers;

public class ConvertKitClient
{
    private readonly HttpClient _client;
    private const string BaseUrl = "https://api.convertkit.com/v3/";

    public ConvertKitClient(string apiKey)
    {
        _client = new HttpClient();
        _client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
        _client.DefaultRequestHeaders.Add("Authorization", $"Bearer {apiKey}");
    }

    // We'll add more methods here soon!
}

Implementing core API functionalities

Now for the fun part! Let's add some methods to interact with subscribers, forms, and sequences.

Subscribers

public async Task<string> GetSubscribers()
{
    var response = await _client.GetAsync($"{BaseUrl}subscribers");
    return await response.Content.ReadAsStringAsync();
}

public async Task<string> AddSubscriber(string email, string firstName = null)
{
    var content = new FormUrlEncodedContent(new[]
    {
        new KeyValuePair<string, string>("email", email),
        new KeyValuePair<string, string>("first_name", firstName)
    });

    var response = await _client.PostAsync($"{BaseUrl}subscribers", content);
    return await response.Content.ReadAsStringAsync();
}

Forms

public async Task<string> GetForms()
{
    var response = await _client.GetAsync($"{BaseUrl}forms");
    return await response.Content.ReadAsStringAsync();
}

public async Task<string> AddSubscriberToForm(int formId, string email)
{
    var content = new FormUrlEncodedContent(new[]
    {
        new KeyValuePair<string, string>("email", email)
    });

    var response = await _client.PostAsync($"{BaseUrl}forms/{formId}/subscribe", content);
    return await response.Content.ReadAsStringAsync();
}

Sequences

public async Task<string> GetSequences()
{
    var response = await _client.GetAsync($"{BaseUrl}sequences");
    return await response.Content.ReadAsStringAsync();
}

public async Task<string> AddSubscriberToSequence(int sequenceId, string email)
{
    var content = new FormUrlEncodedContent(new[]
    {
        new KeyValuePair<string, string>("email", email)
    });

    var response = await _client.PostAsync($"{BaseUrl}sequences/{sequenceId}/subscribe", content);
    return await response.Content.ReadAsStringAsync();
}

Error handling and rate limiting

Let's add some resilience to our code:

private async Task<HttpResponseMessage> SendRequestWithRetry(Func<Task<HttpResponseMessage>> request)
{
    int maxRetries = 3;
    int delay = 1000;

    for (int i = 0; i < maxRetries; i++)
    {
        var response = await request();
        
        if (response.IsSuccessStatusCode)
            return response;

        if (response.StatusCode == System.Net.HttpStatusCode.TooManyRequests)
        {
            await Task.Delay(delay);
            delay *= 2;
        }
        else
        {
            throw new HttpRequestException($"Request failed: {response.StatusCode}");
        }
    }

    throw new HttpRequestException("Max retries reached");
}

Now, wrap your API calls with this method for better error handling and rate limit respect.

Creating a simple CLI interface

Let's whip up a quick CLI to test our integration:

class Program
{
    static async Task Main(string[] args)
    {
        Console.Write("Enter your ConvertKit API key: ");
        var apiKey = Console.ReadLine();

        var client = new ConvertKitClient(apiKey);

        while (true)
        {
            Console.WriteLine("\nChoose an action:");
            Console.WriteLine("1. List subscribers");
            Console.WriteLine("2. Add subscriber");
            Console.WriteLine("3. Exit");

            var choice = Console.ReadLine();

            switch (choice)
            {
                case "1":
                    var subscribers = await client.GetSubscribers();
                    Console.WriteLine(subscribers);
                    break;
                case "2":
                    Console.Write("Enter email: ");
                    var email = Console.ReadLine();
                    var result = await client.AddSubscriber(email);
                    Console.WriteLine(result);
                    break;
                case "3":
                    return;
                default:
                    Console.WriteLine("Invalid choice");
                    break;
            }
        }
    }
}

Testing the integration

Don't forget to write some unit tests! Here's a quick example using xUnit:

public class ConvertKitClientTests
{
    [Fact]
    public async Task GetSubscribers_ReturnsValidResponse()
    {
        var client = new ConvertKitClient("your-api-key");
        var result = await client.GetSubscribers();
        Assert.Contains("subscribers", result);
    }
}

Best practices and optimization

Use async/await consistently for better performance.
Implement caching for frequently accessed data.
Consider using a dependency injection container for managing your ConvertKitClient instance.

Conclusion

Congratulations! You've just built a solid foundation for your ConvertKit API integration in C#. From here, you can expand on this base, add more features, or integrate it into your existing projects.

Remember, the key to a great integration is continuous improvement. Keep an eye on ConvertKit's API updates and don't be afraid to refactor and optimize as you go.

Additional resources

Happy coding, and may your email lists grow and your campaigns convert!