Combine Predicates and Actions for a clean and efficient way to manage in memory lists.

CleanCache.cs

using System.Globalization;

var _cache = new Dictionary<string, CacheItem<Transfer>>() {
    { "1", new CacheItem<Transfer> { Item = new Transfer { Id = 100, Status = TransferStatus.Completed, LastModified = DateTime.ParseExact("2024-07-16 11:00", "yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture) }  } },
    { "2", new CacheItem<Transfer> { Item = new Transfer { Id = 200, Status = TransferStatus.Incomplete, LastModified = DateTime.ParseExact("2024-07-16 11:00", "yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture) }  } },
    { "3", new CacheItem<Transfer> { Item = new Transfer { Id = 300, Status = TransferStatus.Canceled, LastModified = DateTime.ParseExact("2024-07-16 11:00", "yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture) }  } },
    };

// Global method to access and clean up cache.
void CleanUpCache<T>(KeyValuePair<string, CacheItem<T>> entry) =>
    _cache.Remove(entry.Key);

// Filter for specific type and condition.
Predicate<KeyValuePair<string, CacheItem<Transfer>>> staleTransfers = transfer =>
    transfer.Value.Item.Status is (TransferStatus.Incomplete or TransferStatus.Canceled)
    &&
    transfer.Value.Item.LastModified.AddHours(1) <= DateTime.Now;

// Execution on each item.
Action<KeyValuePair<string, CacheItem<Transfer>>> removeStaleTransfers = transfer =>
    CleanUpCache(transfer);

// Do work.
_cache.ToList().FindAll(staleTransfers).ForEach(removeStaleTransfers);

public class CacheItem<T>
{
    public T Item { get; set; }
}

public partial class Transfer
{
    public int Id { get; set; }
    public TransferStatus Status { get; set; }
    public DateTime LastModified { get; set; }
}
public enum TransferStatus : int
{
    Completed = 1,
    Incomplete = 2,
    Canceled = 3,
    AwaitingFunds = 4
}

Predicates, Funcs and Actions can make your life so much easier.

Simply put they offer a way to pass around a method as a parameter and combing them can be an effective strategy.

This example showcases how to take care of managing a cache dictionary, cleaning it up by removing drop-offs older than 1 hour. This effectively leads to better memory usage and faster response times as the cache is kept to a minimum, all while enforcing clean, extendable, and testable code.

This implementation can also be extended to support abandoned order baskets, placing back orders for specific products or even sending out a reengagement notification.

In summary, Func is for returning values, Action is for performing actions, and Predicate is a specialized form of Func<T, bool> for boolean evaluations.

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