Implement In-Memory Cache In The .NET Core API

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!