A Simple Example of Using the Memory Cache in .NET 6 with API Endpoints

It took me a little longer than I expected to write the code for this example, and whenever that happens I assume it will take some other people more time than they expect too. That is why I am writing it down.

In principle it is very simple, I want to use a MemoryCache inside an API endpoint. When the endpoint is called, the memory cache is injected into it.

I check the cache for the key I’m looking for. If the key is in the cache, I return the value. If the key is not in the cache, I do a fake lookup in the database, and then I add the key and value to the cache.

Once the code is complete it is very clear and easy to read, so I won’t add anything else. Hope this helps you.

 1using Microsoft.Extensions.Caching.Memory;
 3var builder = WebApplication.CreateBuilder(args);
 5// Add services to the container.
 6builder.Services.AddMemoryCache(); // add the memory cache to the service collection
 7builder.Services.AddSingleton<Random>(); // add the random number generator to the service collection
 8var app = builder.Build();
10app.MapGet("/Inventory/{itemId}", (int itemId, IMemoryCache memoryCache, Random random) =>
12    Console.WriteLine($"You requested item:{itemId}, looking in cache...");
13    if (memoryCache.TryGetValue<int>(itemId, out var quantity))
14    {
15        Console.WriteLine($"Found item:{itemId}, in the cache!");
16        return Results.Ok($"Found item:{itemId}, in the cache. We have {quantity} in stock.");
17    }
18    else
19    {
20        Console.WriteLine("Could not find id:{id} in the cache! Searching the database...");
21        // Not really going to look in the database
22        quantity = random.Next(100);
23        memoryCache.Set(itemId, quantity, TimeSpan.FromSeconds(10));
24        return Results.Ok($"Found item:{itemId} in the database. We have {quantity} in stock. Adding it to the cache now.");
25    }   
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