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Advanced Patterns

Query Caching with HybridCache

For automatic query caching, use the DSoftStudio.Mediator.HybridCache companion package — it provides ICachedRequest, CachingBehavior, and AddMediatorHybridCache() out of the box.

If you prefer a manual approach without the package dependency, you can write a custom caching behavior in ~30 lines. The pattern below constrains the behavior to queries only (via IQuery<TResponse>):

public interface ICachedQuery
{
    string CacheKey => $"{GetType().Name}:{this}";
    static virtual TimeSpan Duration => TimeSpan.FromSeconds(60);
}

public sealed class QueryCacheBehavior<TRequest, TResponse>
    : IPipelineBehavior<TRequest, TResponse>
    where TRequest : IQuery<TResponse>, ICachedQuery
{
    private readonly HybridCache _cache;

    public QueryCacheBehavior(HybridCache cache) => _cache = cache;

    public async ValueTask<TResponse> Handle(
        TRequest request,
        IRequestHandler<TRequest, TResponse> next,
        CancellationToken ct)
    {
        return await _cache.GetOrCreateAsync(
            request.CacheKey,
            async token => await next.Handle(request, token),
            new HybridCacheEntryOptions { Expiration = TRequest.Duration },
            cancellationToken: ct);
    }
}

// Registration
services.AddHybridCache();
services.AddTransient(typeof(IPipelineBehavior<,>), typeof(QueryCacheBehavior<,>));