Bits of .NET

⚡ 100x Faster Responses with One Line of Code

Same endpoint called repeatedly? Database query every time? Output caching stores HTTP responses. No database, no processing.

📝 Basic Output Caching

// Program.cs
builder.Services.AddOutputCache();

app.UseOutputCache();

// Controller
[ApiController]
[Route("api/[controller]")]
public class ProductsController : ControllerBase
{
    [HttpGet]
    [OutputCache(Duration = 60)]  // Cache for 60 seconds
    public async Task> GetProducts()
    {
        return await _context.Products.ToListAsync();
    }
    
    [HttpGet("{id}")]
    [OutputCache(Duration = 300, VaryByQueryKeys = new[] { "id" })]
    public async Task GetProduct(int id)
    {
        return await _context.Products.FindAsync(id);
    }
}

🎯 Advanced Configuration

builder.Services.AddOutputCache(options =>
{
    options.AddPolicy("LongCache", policy =>
    {
        policy.Expire(TimeSpan.FromHours(1))
              .SetVaryByQuery("search", "page")
              .Tag("products");
    });
    
    options.AddPolicy("NoCacheForAdmin", policy =>
    {
        policy.Expire(TimeSpan.FromSeconds(10))
              .VaryByUser();
    });
});

// Usage
[HttpGet]
[OutputCache(PolicyName = "LongCache")]
public async Task> GetProducts() { }

// Invalidate cache
[HttpPost]
public async Task CreateProduct(Product product)
{
    await _context.Products.AddAsync(product);
    await _context.SaveChangesAsync();
    
    await _outputCacheStore.EvictByTagAsync("products", CancellationToken.None);
    
    return CreatedAtAction(nameof(GetProduct), new { id = product.Id }, product);
}

💡 When to Use

• Read-only endpoints (GET requests)
• Public data (same for all users)
• Expensive database queries
• External API calls that change rarely
• Static reference data (country lists, categories)