Easily Use Redis Cache In ASP.NET 6.0 Web API

using HtmlAgilityPack;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Caching.Distributed;
using RedisCacheASP.NET6.Models;
using System.Globalization;
using System.Net;
using System.Text;
using System.Text.Json;
using System.Xml.Linq;

namespace RedisCacheASP.NET6.Controllers
{
    [Route("[controller]")]
    [ApiController]
    public class AnalyticsController : ControllerBase
    {
        readonly CultureInfo culture = new("en-US");
        private readonly MyDbContext _dbContext;
        private readonly IConfiguration _configuration;
        private static readonly object _lockObj = new();
        private readonly IDistributedCache _cache;
        public AnalyticsController(MyDbContext context, IConfiguration configuration, IDistributedCache cache)
        {
            _dbContext = context;
            _configuration = configuration;
            _cache = cache;
        }

        [HttpPost]
        [Route("CreatePosts/{authorId}")]
        public async Task<bool> CreatePosts(string authorId)
        {
            try
            {
                XDocument doc = XDocument.Load("https://www.c-sharpcorner.com/members/" + authorId + "/rss");
                if (doc == null)
                {
                    return false;
                }
                var entries = from item in doc.Root.Descendants().First(i => i.Name.LocalName == "channel").Elements().Where(i => i.Name.LocalName == "item")
                              select new Feed
                              {
                                  Content = item.Elements().First(i => i.Name.LocalName == "description").Value,
                                  Link = (item.Elements().First(i => i.Name.LocalName == "link").Value).StartsWith("/") ? "https://www.c-sharpcorner.com" + item.Elements().First(i => i.Name.LocalName == "link").Value : item.Elements().First(i => i.Name.LocalName == "link").Value,
                                  PubDate = Convert.ToDateTime(item.Elements().First(i => i.Name.LocalName == "pubDate").Value, culture),
                                  Title = item.Elements().First(i => i.Name.LocalName == "title").Value,
                                  FeedType = (item.Elements().First(i => i.Name.LocalName == "link").Value).ToLowerInvariant().Contains("blog") ? "Blog" : (item.Elements().First(i => i.Name.LocalName == "link").Value).ToLowerInvariant().Contains("news") ? "News" : "Article",
                                  Author = item.Elements().First(i => i.Name.LocalName == "author").Value
                              };

                List<Feed> feeds = entries.OrderByDescending(o => o.PubDate).ToList();
                string urlAddress = string.Empty;
                List<ArticleMatrix> articleMatrices = new();
                _ = int.TryParse(_configuration["ParallelTasksCount"], out int parallelTasksCount);

                Parallel.ForEach(feeds, new ParallelOptions { MaxDegreeOfParallelism = parallelTasksCount }, feed =>
                {
                    urlAddress = feed.Link;

                    var httpClient = new HttpClient
                    {
                        BaseAddress = new Uri(urlAddress)
                    };
                    var result = httpClient.GetAsync("").Result;

                    string strData = "";

                    if (result.StatusCode == HttpStatusCode.OK)
                    {
                        strData = result.Content.ReadAsStringAsync().Result;

                        HtmlDocument htmlDocument = new();
                        htmlDocument.LoadHtml(strData);

                        ArticleMatrix articleMatrix = new()
                        {
                            AuthorId = authorId,
                            Author = feed.Author,
                            Type = feed.FeedType,
                            Link = feed.Link,
                            Title = feed.Title,
                            PubDate = feed.PubDate
                        };

                        string category = "Videos";
                        if (htmlDocument.GetElementbyId("ImgCategory") != null)
                        {
                            category = htmlDocument.GetElementbyId("ImgCategory").GetAttributeValue("title", "");
                        }

                        articleMatrix.Category = category;

                        var view = htmlDocument.DocumentNode.SelectSingleNode("//span[@id='ViewCounts']");
                        if (view != null)
                        {
                            articleMatrix.Views = view.InnerText;

                            if (articleMatrix.Views.Contains('m'))
                            {
                                articleMatrix.ViewsCount = decimal.Parse(articleMatrix.Views[0..^1]) * 1000000;
                            }
                            else if (articleMatrix.Views.Contains('k'))
                            {
                                articleMatrix.ViewsCount = decimal.Parse(articleMatrix.Views[0..^1]) * 1000;
                            }
                            else
                            {
                                _ = decimal.TryParse(articleMatrix.Views, out decimal viewCount);
                                articleMatrix.ViewsCount = viewCount;
                            }
                        }
                        else
                        {
                            var newsView = htmlDocument.DocumentNode.SelectSingleNode("//span[@id='spanNewsViews']");
                            if (newsView != null)
                            {
                                articleMatrix.Views = newsView.InnerText;

                                if (articleMatrix.Views.Contains('m'))
                                {
                                    articleMatrix.ViewsCount = decimal.Parse(articleMatrix.Views[0..^1]) * 1000000;
                                }
                                else if (articleMatrix.Views.Contains('k'))
                                {
                                    articleMatrix.ViewsCount = decimal.Parse(articleMatrix.Views[0..^1]) * 1000;
                                }
                                else
                                {
                                    _ = decimal.TryParse(articleMatrix.Views, out decimal viewCount);
                                    articleMatrix.ViewsCount = viewCount;
                                }
                            }
                            else
                            {
                                articleMatrix.ViewsCount = 0;
                            }
                        }
                        var like = htmlDocument.DocumentNode.SelectSingleNode("//span[@id='LabelLikeCount']");
                        if (like != null)
                        {
                            _ = int.TryParse(like.InnerText, out int likes);
                            articleMatrix.Likes = likes;
                        }

                        lock (_lockObj)
                        {
                            articleMatrices.Add(articleMatrix);
                        }
                    }
                });

                _dbContext.ArticleMatrices.RemoveRange(_dbContext.ArticleMatrices.Where(x => x.AuthorId == authorId));

                foreach (ArticleMatrix articleMatrix in articleMatrices)
                {
                    if (articleMatrix.Category == "Videos")
                    {
                        articleMatrix.Type = "Video";
                    }
                    articleMatrix.Category = articleMatrix.Category.Replace("&", "&");
                    await _dbContext.ArticleMatrices.AddAsync(articleMatrix);
                }

                await _dbContext.SaveChangesAsync();
                await _cache.RemoveAsync(authorId);
                return true;
            }
            catch
            {
                return false;
            }
        }

        [HttpGet]
        [Route("GetAll/{authorId}/{enableCache}")]
        public async Task<List<ArticleMatrix>> GetAll(string authorId, bool enableCache)
        {
            if (!enableCache)
            {
                return _dbContext.ArticleMatrices.Where(x => x.AuthorId == authorId).OrderByDescending(x => x.PubDate).ToList();
            }
            string cacheKey = authorId;

            // Trying to get data from the Redis cache
            byte[] cachedData = await _cache.GetAsync(cacheKey);
            List<ArticleMatrix> articleMatrices = new();
            if (cachedData != null)
            {
                // If the data is found in the cache, encode and deserialize cached data.
                var cachedDataString = Encoding.UTF8.GetString(cachedData);
                articleMatrices = JsonSerializer.Deserialize<List<ArticleMatrix>>(cachedDataString);
            }
            else
            {
                // If the data is not found in the cache, then fetch data from database
                articleMatrices = _dbContext.ArticleMatrices.Where(x => x.AuthorId == authorId).OrderByDescending(x => x.PubDate).ToList();

                // Serializing the data
                string cachedDataString = JsonSerializer.Serialize(articleMatrices);
                var dataToCache = Encoding.UTF8.GetBytes(cachedDataString);

                // Setting up the cache options 
                DistributedCacheEntryOptions options = new DistributedCacheEntryOptions()
                    .SetAbsoluteExpiration(DateTime.Now.AddMinutes(5))
                    .SetSlidingExpiration(TimeSpan.FromMinutes(3));

                // Add the data into the cache
                await _cache.SetAsync(cacheKey, dataToCache, options);
            }
            return articleMatrices;
        }
    }
}

We have two methods inside the above controller.

“CreatePosts” will fetch the authored posts data for a particular C# Corner author and save to the database.

GetAll method in AnalyticsController.cs

        [HttpGet]
        [Route("GetAll/{authorId}/{enableCache}")]
        public async Task<List<ArticleMatrix>> GetAll(string authorId, bool enableCache)
        {
            if (!enableCache)
            {
                return _dbContext.ArticleMatrices.Where(x => x.AuthorId == authorId).OrderByDescending(x => x.PubDate).ToList();
            }
            string cacheKey = authorId;

            // Trying to get data from the Redis cache
            byte[] cachedData = await _cache.GetAsync(cacheKey);
            List<ArticleMatrix> articleMatrices = new();
            if (cachedData != null)
            {
                // If the data is found in the cache, encode and deserialize cached data.
                var cachedDataString = Encoding.UTF8.GetString(cachedData);
                articleMatrices = JsonSerializer.Deserialize<List<ArticleMatrix>>(cachedDataString);
            }
            else
            {
                // If the data is not found in the cache, then fetch data from database
                articleMatrices = _dbContext.ArticleMatrices.Where(x => x.AuthorId == authorId).OrderByDescending(x => x.PubDate).ToList();

                // Serializing the data
                string cachedDataString = JsonSerializer.Serialize(articleMatrices);
                var dataToCache = Encoding.UTF8.GetBytes(cachedDataString);

                // Setting up the cache options 
                DistributedCacheEntryOptions options = new DistributedCacheEntryOptions()
                    .SetAbsoluteExpiration(DateTime.Now.AddMinutes(5))
                    .SetSlidingExpiration(TimeSpan.FromMinutes(3));

                // Add the data into the cache
                await _cache.SetAsync(cacheKey, dataToCache, options);
            }
            return articleMatrices;
        }

“GetAll” method will fetch the data from the database/cache for an author. I have added a parameter “enableCache” in this method to examine the performance of Caching.

When we are fetching the data for an author, first it will check inside the cache using author id as a key. If the data is available, it will deserialize the data to model and return. But if the data is not available or expired, data will be fetched from the database and set to the Redis cache.

We must change the Program.cs class with the code change below. So that, the Entity framework connection and Redis cache connection have been provided.

Program.cs

using Microsoft.EntityFrameworkCore;
using RedisCacheASP.NET6.Models;

var builder = WebApplication.CreateBuilder(args);
ConfigurationManager configuration = builder.Configuration;

// Add services to the container.

builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

builder.Services.AddDbContext<MyDbContext>(options => options.UseSqlServer(configuration.GetConnectionString("ConnStr")));
builder.Services.AddStackExchangeRedisCache(options => { options.Configuration = configuration["RedisCacheUrl"]; });

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseAuthorization();

app.MapControllers();

app.Run();

We can create the SQL database and table using migration commands.

We can use the command below to create migration scripts in Package Manager Console.

PM > add-migration InititalScript

Above command will create a new migration script. We can use the script below to create our database and table.

PM> update-database

We can run the application and use Postman tool to create few C# Corner posts data and save to the database.

We must run our local Redis cache server as well. (Execute redis-server.exe file)

We can create posts for a particular C# Corner author. Here I am using my own author id. (You can get the author id from C# Corner profile)

There are 100 post details created for my author id. We can try to fetch these data in Postman.

Please note that it has taken 21 milliseconds to fetch the data. Because there is no data available in the cache and data is fetched directly from the database.

Now we can try to fetch the data again.

We can notice that there is a significant performance improvement. It just took 5 milliseconds only. Because data is fetched from Redis cache instead of database.

Now we can fetch the data without Caching. We have already added a parameter in the “GetAll” method to enable or disable cache.

This time data is fetched directly from database because we have passed cache flag as false. We can notice that it took 30 milliseconds to fetch the same data from database. If you are fetching huge data from a database, you can see more improvement using Redis cache.

Now we can create an Azure cache for Redis and check with our application.

Create Azure Cache for Redis on Azure Portal

Choose Azure Cache for Redis from Databases tab.

We can create a new resource group or choose any existing resource group and give a valid name for Redis instance. There are various pricing plans available for Redis cache. I have chosen the basic plan for testing purposes.

Choose the Redis version. By default, the selected version is 4. Currently, there are two versions available. I have chosen version 6 for our Redis cache.

After validation passed, we can click “Create” button to start the deployment.

Deployment will take some time. After deployment, we can open the resource and click on Show access keys link.

This will open a pop-up window and show various cache keys. We can choose the Primary connection string.

Get this primary connection string and replace it in appsetting (Currently, we have given local Redis server connection string).

Now we can run the application without our local Redis server.

If we are hosting our application on Azure, we can see significant performance improvement while using the Azure Redis cache.

Conclusion

In this post, we have discussed distributed caching and Redis cache. We have seen how to install and test the Redis cache server on Windows machine. We have then created an ASP.NET 6.0 Web API and it is used with the local Redis server on Windows. We have also seen how to create an Azure cache for Redis on Azure portal and used it with our application.