SendGrid API API in C#

SendGrid API API in C#

This guide shows you how to integrate the SendGrid API into your C# application. Email API for transactional and marketing email with templates and analytics.

Prerequisites

  • C# installed on your system
  • An SendGrid API API key (sign up at https://sendgrid.com)
  • Basic familiarity with HTTP APIs

Installation

dotnet add package RestSharp
dotnet add package Newtonsoft.Json

Basic Usage

using System;
using System.Net.Http;
using System.Threading.Tasks;

class Program {
    private static readonly string ApiKey = Environment.GetEnvironmentVariable("API_KEY") ?? "YOUR_API_KEY";
    private static readonly string BaseUrl = "https://api.sendgrid.com";

    static async Task Main(string[] args) {
        using var client = new HttpClient();
        client.DefaultRequestHeaders.Add("Authorization", $"Bearer {ApiKey}");

        var response = await client.GetAsync($"{BaseUrl}/v1/resources");
        Console.WriteLine($"Status: {(int)response.StatusCode}");
        var body = await response.Content.ReadAsStringAsync();
        Console.WriteLine(body);
    }
}

Error Handling

using System;
using System.Net.Http;
using System.Threading.Tasks;

class Program {
    private static readonly string ApiKey = Environment.GetEnvironmentVariable("API_KEY") ?? "YOUR_API_KEY";

    static async Task<string> CallApiWithRetry(string url, int maxRetries = 3) {
        using var client = new HttpClient();
        client.DefaultRequestHeaders.Add("Authorization", $"Bearer {ApiKey}");

        for (int attempt = 0; attempt < maxRetries; attempt++) {
            try {
                var response = await client.GetAsync(url);

                if ((int)response.StatusCode == 429) {
                    Console.WriteLine("Rate limited. Waiting...");
                    await Task.Delay(60000);
                    continue;
                }

                response.EnsureSuccessStatusCode();
                return await response.Content.ReadAsStringAsync();
            } catch (Exception e) {
                Console.WriteLine($"Attempt {attempt + 1} failed: {e.Message}");
                if (attempt == maxRetries - 1) throw;
                await Task.Delay((int)Math.Pow(2, attempt) * 1000);
            }
        }
        throw new Exception("Max retries exceeded");
    }

    static async Task Main() {
        var result = await CallApiWithRetry("https://api.sendgrid.com/v1/resources");
        Console.WriteLine(result);
    }
}

Advanced Usage

using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Text;
using System.Text.Json;
using System.Threading.Tasks;

public class SendgridClient {
    private readonly string _apiKey;
    private readonly string _baseUrl;
    private readonly HttpClient _httpClient;

    public SendgridClient(string apiKey, string baseUrl = "https://api.sendgrid.com") {
        _apiKey = apiKey;
        _baseUrl = baseUrl.TrimEnd('/');
        _httpClient = new HttpClient { Timeout = TimeSpan.FromSeconds(30) };
        _httpClient.DefaultRequestHeaders.Add("Authorization", $"Bearer {_apiKey}");
        _httpClient.DefaultRequestHeaders.Add("User-Agent", "SendGrid API/1.0");
    }

    public async Task<string> ListResourcesAsync() {
        var response = await _httpClient.GetAsync($"{_baseUrl}/v1/resources");
        response.EnsureSuccessStatusCode();
        return await response.Content.ReadAsStringAsync();
    }

    public async Task<string> CreateResourceAsync(object data) {
        var json = JsonSerializer.Serialize(data);
        var content = new StringContent(json, Encoding.UTF8, "application/json");
        var response = await _httpClient.PostAsync($"{_baseUrl}/v1/resources", content);
        response.EnsureSuccessStatusCode();
        return await response.Content.ReadAsStringAsync();
    }

    public async Task<string> GetResourceAsync(string id) {
        var response = await _httpClient.GetAsync($"{_baseUrl}/v1/resources/{id}");
        response.EnsureSuccessStatusCode();
        return await response.Content.ReadAsStringAsync();
    }
}

class Program {
    static async Task Main() {
        var client = new SendgridClient(Environment.GetEnvironmentVariable("API_KEY")!);
        var resources = await client.ListResourcesAsync();
        Console.WriteLine(resources);
    }
}

Best Practices

  • Store your API key in an environment variable, never in source code
  • Implement retry logic with exponential backoff for 429 and 5xx errors
  • Set reasonable timeouts (10-30 seconds) for all API calls
  • Log request IDs from response headers for debugging
  • Cache responses where appropriate to reduce API calls

Other languages