Implement In-Memory Cache In The .NET Core API

We are going to discuss Caching in .NET Core and how it works. So, we look at the following things one by one.

• Introduction of Caching
• What is Cache
• Types of cache
• Cache Implementation

So, let’s start one by one.

Introduction

Caching is very popular nowadays in the software industry because it will improve the performance and scalability of the application, as we use and see many web applications like G-mail and Facebook and how responsive they are and great user experience while we using that. There are a lot of users using the internet and if an application has huge network traffic and demand and due to that we need to take care of many things which help us to improve the performance and responsiveness of the application. So, because of that, there is one of the solutions is caching and that’s why caching comes into the picture.

What is Caching?

The cache is the memory storage that is used to store the frequent access data into the temporary storage, it will improve the performance drastically and avoid the unnecessary database hit and store frequently used data into the buffer whenever we need it.

As you see in the above image there are two scenarios one is without using cache and another is with cache and how it works. So here when we do not use the cache, in that case, suppose users want data then they will hit each time database and it will increase the time complexity and reduce performance. In case there are some static data users want and it is same for all users, in that case when we do not use cache then each one hit the unnecessary database to fetch data. And on the other side as you can see if we use cache and in that case, if there same static and same data for all users then only the first user will hit the database and fetch data and store it into the cache memory and then other two users use that from the cache without unnecessarily hitting the database to fetch data.

Types of Cache

Basically, there are two types of caching .NET Core supports

1. In-Memory Caching
2. Distributed Caching

When we use In-Memory Cache then in that case data is stored in the application server memory and whenever we need then we fetch data from that and use it wherever we need it. And in Distributed Caching there are many third-party mechanisms like Redis and many others. But in this section, we look into the In-Memory Cache in detail and how it works in .NET Core.

In-Memory Cache

Basically, In-Memory Cache is used for lightweight and small applications and that will work well in that. It stores data into the server memory on the application side and users use that whenever need arises.

Advantages of In-Memory Cache

• Users fetch data rapidly when we use In-Memory Cache.
• It will increase the performance of the application.
• Best suited for small application which is deployed on a single server.

Disadvantages of In-Memory Cache

• Sometimes In-Memory cache increases the maintenance of the application
• In the In-Memory Cache data is persisted on a single server and if the server will crash then data is lost. Also it’s hard to scale the application in some scenarios.

Now we are going to create one .NET Core API, implement the caching into that and understand how the things are going to work.

Step 1

Create the .NET Core API Web Application

Step 2

Install the following NuGet Packages which need step by step in our application

• Microsoft.EntityFrameworkCore
• Microsoft.EntityFrameworkCore.Design
• Microsoft.EntityFrameworkCore.SqlServer
• Microsoft.EntityFrameworkCore.Tools
• Swashbuckle.AspNetCore
• System.Runtime.Caching

Step 3

Create the Model folder and create one Product Class inside that with details

namespace MemoryCacheDemo.Model
{
    public class Product
    {
        public int ProductId { get; set; }
        public string ProductName { get; set; }
        public string ProductDescription { get; set; }
        public int Stock { get; set; }
    }
}

Step 4

Next, Create the DbContextClass Class for Database related operations as I have shown below

using MemoryCacheDemo.Model;
using Microsoft.EntityFrameworkCore;
namespace MemoryCacheDemo.Data {
    public class DbContextClass: DbContext {
        public DbContextClass(DbContextOptions < DbContextClass > options): base(options) {}
        public DbSet < Product > Products {
            get;
            set;
        }
    }
}

Step 5

Now, we are going to create ICacheService Interface and CacheService Class for In-Memory Cache-related usage.

using System;
using System.Collections.Generic;

namespace MemoryCacheDemo.Cache
{
    public interface ICacheService
    {
        /// <summary>
        /// Get Data using key
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="key"></param>
        /// <returns></returns>
        T GetData<T>(string key);

        /// <summary> 
        /// Set Data with Value and Expiration Time of Key
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="key"></param>
        /// <param name="value"></param>
        /// <param name="expirationTime"></param>
        /// <returns></returns>
        bool SetData<T>(string key, T value, DateTimeOffset expirationTime);

        /// <summary>
        /// Remove Data 
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        object RemoveData(string key);
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Caching;
namespace MemoryCacheDemo.Cache {
    public class CacheService: ICacheService {
        ObjectCache _memoryCache = MemoryCache.Default;
        public T GetData < T > (string key) {
            try {
                T item = (T) _memoryCache.Get(key);
                return item;
            } catch (Exception e) {
                throw;
            }
        }
        public bool SetData < T > (string key, T value, DateTimeOffset expirationTime) {
            bool res = true;
            try {
                if (!string.IsNullOrEmpty(key)) {
                    _memoryCache.Set(key, value, expirationTime);
                }
            } catch (Exception e) {
                throw;
            }
            return res;
        }
        public object RemoveData(string key) {
            try {
                if (!string.IsNullOrEmpty(key)) {
                    return _memoryCache.Remove(key);
                }
            } catch (Exception e) {
                throw;
            }
            return false;
        }
    }
}

Step 6

Create the ProductController class, create the following method as shown below

using MemoryCacheDemo.Cache;
using MemoryCacheDemo.Data;
using MemoryCacheDemo.Model;
using Microsoft.AspNetCore.Mvc;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
namespace MemoryCacheDemo.Controllers {
    [Route("api/[controller]")]
    [ApiController]
    public class ProductController: ControllerBase {
        private readonly DbContextClass _dbContext;
        private readonly ICacheService _cacheService;
        public ProductController(DbContextClass dbContext, ICacheService cacheService) {
                _dbContext = dbContext;
                _cacheService = cacheService;
            }
            [HttpGet("products")]
        public IEnumerable < Product > Get() {
                var cacheData = _cacheService.GetData < IEnumerable < Product >> ("product");
                if (cacheData != null) {
                    return cacheData;
                }
                var expirationTime = DateTimeOffset.Now.AddMinutes(5.0);
                cacheData = _dbContext.Products.ToList();
                _cacheService.SetData < IEnumerable < Product >> ("product", cacheData, expirationTime);
                return cacheData;
            }
            [HttpGet("product")]
        public Product Get(int id) {
                Product filteredData;
                var cacheData = _cacheService.GetData < IEnumerable < Product >> ("product");
                if (cacheData != null) {
                    filteredData = cacheData.Where(x => x.ProductId == id).FirstOrDefault();
                    return filteredData;
                }
                filteredData = _dbContext.Products.Where(x => x.ProductId == id).FirstOrDefault();
                return filteredData;
            }
            [HttpPost("addproduct")]
        public async Task < Product > Post(Product value) {
                var obj = await _dbContext.Products.AddAsync(value);
                _cacheService.RemoveData("product");
                _dbContext.SaveChanges();
                return obj.Entity;
            }
            [HttpPut("updateproduct")]
        public void Put(Product product) {
                _dbContext.Products.Update(product);
                _cacheService.RemoveData("product");
                _dbContext.SaveChanges();
            }
            [HttpDelete("deleteproduct")]
        public void Delete(int Id) {
            var filteredData = _dbContext.Products.Where(x => x.ProductId == Id).FirstOrDefault();
            _dbContext.Remove(filteredData);
            _cacheService.RemoveData("product");
            _dbContext.SaveChanges();
        }
    }
}

Step 7

Add the SQL Server connection string inside appsetting.json

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  },
  "AllowedHosts": "*",
  "ConnectionStrings": {
    "DefaultConnection": "Data Source=server;Initial Catalog=MemoryCache;User Id=****;Password=***;"
  }
}

Step 8

Next, Register the ICacheService inside Configure Service method of Startup Class and also add some configuration related to Swagger to test our API endpoints

using MemoryCacheDemo.Cache;
using MemoryCacheDemo.Data;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.OpenApi.Models;
namespace MemoryCacheDemo {
    public class Startup {
        public Startup(IConfiguration configuration) {
            Configuration = configuration;
        }
        public IConfiguration Configuration {
            get;
        }
        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services) {
            services.AddControllers();
            services.AddScoped < ICacheService, CacheService > ();
            services.AddDbContext < DbContextClass > (options => options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
            services.AddSwaggerGen(c => {
                c.SwaggerDoc("v1", new OpenApiInfo {
                    Title = "MemoryCacheDemo", Version = "v1"
                });
            });
        }
        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env) {
            if (env.IsDevelopment()) {
                app.UseDeveloperExceptionPage();
                app.UseSwagger();
                app.UseSwaggerUI(c => c.SwaggerEndpoint("/swagger/v1/swagger.json", "MemoryCacheDemo v1"));
            }
            app.UseHttpsRedirection();
            app.UseRouting();
            app.UseAuthorization();
            app.UseEndpoints(endpoints => {
                endpoints.MapControllers();
            });
        }
    }
}

Step 9

Perform Migration and Database Update for DB Creation using the following commands in Package Manager Console.

add-migration “FirstMigration”

update-database

So, when you enter and execute this command it will generate few things related to migration and create the database inside SQL Server as you put inside Connection String in the appsetting.json

Step 10

Finally, run the application and add the data using swagger UI and then check how caching works inside products and product endpoint.

Basically, I added cache into the product and products endpoints in the controller, as you see when the user wants to fetch data of all products then firstly it will check whether the data is present inside the In-Memory Cache or not and if it’s present inside the cache then return that data to the user and if the data is not present inside the cache, then it will fetch the data from database and also, set that into the cache. So next time user will get that from cache only and avoid hitting the database unnecessarily 

Also, when the user wants to fetch data by using product id as you see in the controller in product second endpoint, we fetch data from cache of all products then filter using product id and if that is present then return to user from cache and if not then fetch from database and return to the user after applying the filter.

So, as you see inside update, delete and post endpoint of Product Controller then we use remove method to remove data of product key which is present inside the cache. So, there are many scenarios and use of memory caches you can use as per your need and requirements. I just want to introduce the basics of the Memory Cache and how it works inside the .NET Core that I covered here.

Also, there is one scenario you need to take care of while using caching like suppose, there are two users using your application then the following scenarios will come

• When the first user sends the request to fetch the data of all products then the first request comes and then it will check if the data is present inside the cache or not and if the data is present inside the cache, then it will fetch the data from database and also set it to the cache.
• Meanwhile, the second user sends the request to get the product details then request also hits the database before completing the first user’s request and because of that second user also hit the database to fetch product details.
• So, there is one solution for this to use the Lock Mechanism as shown below

Add create a lock object top of the class and then in the method as I showed below

private static object _lock = new object();

 

public IEnumerable < Product > Get() {
    var cacheData = _cacheService.GetData < IEnumerable < Product >> ("product");
    if (cacheData != null) {
        return cacheData;
    }
    lock(_lock) {
        var expirationTime = DateTimeOffset.Now.AddMinutes(5.0);
        cacheData = _dbContext.Products.ToList();
        _cacheService.SetData < IEnumerable < Product >> ("product", cacheData, expirationTime);
    }
    return cacheData;
}

So here as you see first, we check if the data is present inside the cache or not if data is available then return that. Next, if the value is not present in the memory cache, then we apply the lock over there and then the request is locked and entered into the section and fetch the product details from the database, and then also set it to the cache and then return the data. So, when the second user sends a request before the user one’s request is complete. So, in that case, the second request is in the queue and after completing the first user request the second request comes into the picture

This is all about In-Memory Cache in .NET Core. I hope you understand things related to that.

Happy Coding!