In-Memory Caching

What is Caching?

Caching stores frequently accessed data in memory to avoid expensive operations like database queries or API calls.

Setup

builder.Services.AddMemoryCache();

Using IMemoryCache

public class ProductsController : Controller
{
    private readonly IMemoryCache _cache;

    public ProductsController(IMemoryCache cache)
    {
        _cache = cache;
    }
}

Setting and Getting Cache

// Set cache
_cache.Set("products", products);

// Get cache
if (_cache.TryGetValue("products", out List<Product> cachedProducts))
{
    return cachedProducts;
}

GetOrCreate Pattern

var products = _cache.GetOrCreate("products", entry =>
{
    entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(5);
    return _context.Products.ToList();
});

Cache Expiration

Absolute Expiration

Cache expires at a specific time.

_cache.Set("products", products, new MemoryCacheEntryOptions
{
    AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(10)
});

Sliding Expiration

Cache expires if not accessed within the time window.

_cache.Set("products", products, new MemoryCacheEntryOptions
{
    SlidingExpiration = TimeSpan.FromMinutes(5)
});

Cache Eviction

_cache.Remove("products");

InvenTrack Example

public class ProductsController : Controller
{
    private readonly IMemoryCache _cache;
    private readonly InvenTrackDbContext _context;

    [HttpGet]
    public async Task<IActionResult> Index()
    {
        const string cacheKey = "products_list";

        // Try get from cache
        if (!_cache.TryGetValue(cacheKey, out List<Product> products))
        {
            // Not in cache, fetch from database
            products = await _context.Products.ToListAsync();

            // Set cache with 5 minute expiration
            var cacheOptions = new MemoryCacheEntryOptions
            {
                AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(5),
                SlidingExpiration = TimeSpan.FromMinutes(2)
            };

            _cache.Set(cacheKey, products, cacheOptions);
        }

        return View(products);
    }

    [HttpPost]
    public async Task<IActionResult> Create(Product product)
    {
        _context.Products.Add(product);
        await _context.SaveChangesAsync();

        // Invalidate cache
        _cache.Remove("products_list");

        return RedirectToAction("Index");
    }
}

Key Takeaways

• Caching: Store data in memory for fast access
• AddMemoryCache(): Register caching service
• IMemoryCache: Inject to use caching
• Set()/Get(): Store and retrieve data
• GetOrCreate(): Get or create if missing
• Absolute expiration: Expires at specific time
• Sliding expiration: Expires if not accessed
• Remove(): Invalidate cache