CacheUtility 1.0.20

CacheUtility

A thread-safe, generic wrapper for System.Runtime.Caching that simplifies cache access and supports powerful caching patterns.

Overview

CacheUtility provides an easy-to-use abstraction over the standard .NET memory cache with additional features:

• Automatic cache population
• Various expiration strategies
• Thread-safe operations
• Support for cache groups
• Dependency relationships between cache groups
• Automatic background refresh functionality

Basic usage

Note: All examples assume you have added the using statement:

using CacheUtility;

Simple caching

The most common pattern is to request an item from the cache, providing a function to generate the item if it doesn't exist:

// Basic usage with default 30-minute sliding expiration
var result = Cache.Get("MyKey", "MyGroupName", () => 
{
    return MyLongRunningTask();
});

Caching with expiration

// With custom sliding expiration
var result = Cache.Get("MyKey", "MyGroupName", TimeSpan.FromHours(1), () => 
{
    return MyLongRunningTask();
});

// With absolute expiration
var result = Cache.Get("MyKey", "MyGroupName", DateTime.Now.AddDays(1), () => 
{
    return MyLongRunningTask();
});

Basic examples

Caching user data

// Cache user data with a sliding expiration
var userData = Cache.Get($"User_{userId}", "UserProfiles", TimeSpan.FromMinutes(30), () =>
{
    return database.GetUserById(userId);
});

Caching application settings

// Cache application settings with absolute expiration
var settings = Cache.Get("GlobalSettings", "AppConfig", DateTime.Now.AddHours(12), () =>
{
    return configurationService.LoadSettings();
});

Async operations

For async operations, you can use the utility with async/await:

var result = await Cache.Get("MyKey", "MyGroupName", async () => 
{
    return await MyLongRunningTaskAsync();
});

Cache management

Removing individual items

Remove a specific item from the cache:

Cache.Remove("MyKey", "MyGroupName");

Group operations

Remove an entire group of cached items:

Cache.RemoveGroup("MyGroupName");

Remove multiple groups:

Cache.RemoveGroup("GroupA", "GroupB", "GroupC");

Retrieving all items from a group

Get all cached items that belong to a specific group:

var allItems = Cache.GetAllByGroup("MyGroupName");

// Iterate through all items in the group
foreach (var kvp in allItems)
{
    Console.WriteLine($"Key: {kvp.Key}, Value: {kvp.Value}");
}

// Access specific items if you know the key
if (allItems.ContainsKey("MySpecificKey"))
{
    var specificItem = allItems["MySpecificKey"];
}

Global cache operations

Clear the entire cache:

Cache.RemoveAll();

Clear the cache except for specific groups:

Cache.RemoveAllButThese(new List<string> { "CriticalData", "ApplicationSettings" });

Intermediate features

Removing multiple items

Remove multiple items that contain specific strings:

Cache.Remove(new List<string> { "UserProfile", "123" }, "UserData");
// This will remove any cache key containing both "UserProfile" and "123"

Working with multiple cached items

// Cache some user data
Cache.Get("User1", "UserData", () => GetUserInfo(1));
Cache.Get("User2", "UserData", () => GetUserInfo(2));
Cache.Get("User3", "UserData", () => GetUserInfo(3));

// Get all cached items from the group
var allUsers = Cache.GetAllByGroup("UserData");
Console.WriteLine($"Found {allUsers.Count} cached users");

// Process each cached item
foreach (var user in allUsers)
{
    Console.WriteLine($"User Key: {user.Key}, Data: {user.Value}");
}

Advanced features

Automatic data refresh

CacheUtility supports automatic background refresh of cached data at specified intervals. This feature ensures your cache stays up-to-date with fresh data while maintaining high performance by serving existing data immediately, even during refresh operations.

Key benefits:

• Non-blocking: Cache calls return immediately with existing data, even when refresh is in progress
• High availability: Your application remains responsive during slow data refresh operations
• Automatic updates: Data stays fresh without manual intervention
• Error resilient: Failed refreshes don't impact cache availability

Basic refresh usage

// Cache data with automatic refresh every 5 minutes
var userData = Cache.Get("user_123", "UserProfiles", 
    TimeSpan.FromHours(1), // Sliding expiration
    () => database.GetUserById(123), // Populate method
    refresh: TimeSpan.FromMinutes(5) // Refresh interval
);

Non-blocking behavior example

// Even if GetExpensiveData() takes 10 seconds to execute,
// subsequent cache calls will return immediately with existing data
var expensiveData = Cache.Get("expensive_key", "DataGroup",
    TimeSpan.FromMinutes(30),
    () => GetExpensiveDataFromAPI(), // Slow operation
    refresh: TimeSpan.FromMinutes(2)
);

// This call returns instantly, even if refresh is running in background
var sameData = Cache.Get("expensive_key", "DataGroup",
    TimeSpan.FromMinutes(30),
    () => GetExpensiveDataFromAPI(),
    refresh: TimeSpan.FromMinutes(2)
);

Real-world refresh scenarios

API data caching:

var weatherData = Cache.Get($"weather_{cityId}", "WeatherCache",
    TimeSpan.FromHours(2), // Cache for 2 hours max, after the cache item last has been accessed
    () => weatherAPI.GetCurrentWeather(cityId),
    refresh: TimeSpan.FromMinutes(15) // Refresh every 15 minutes
);

Database result caching:

var reports = Cache.Get("monthly_reports", "Reports",
    TimeSpan.FromHours(4),
    () => database.GenerateMonthlyReports(), // Expensive query
    refresh: TimeSpan.FromHours(1) // Refresh hourly
);

Configuration data:

var config = Cache.Get("app_config", "Configuration",
    TimeSpan.FromDays(1),
    () => configService.LoadConfiguration(),
    refresh: TimeSpan.FromMinutes(30) // Check for config updates every 30 minutes
);

Cache removal callbacks

CacheUtility supports optional removal callbacks that are invoked when cached items are removed from the cache. This is useful for cleanup operations, logging, or triggering dependent actions.

Basic removal callback

var result = Cache.Get("MyKey", "MyGroupName", 
    DateTime.Now.AddHours(1), // Either Absolute expiration
    TimeSpan.FromMinutes(10), // Or Sliding expiration
    CacheItemPriority.Default, // Priority
    () => MyLongRunningTask(),
    removedCallback: (args) => // Optional callback
    {
        Console.WriteLine($"Cache item removed. Key: {args.CacheItem.Key}, Reason: {args.RemovedReason}");
    });

Removal reasons

The callback provides a CacheEntryRemovedArguments object that contains:

• CacheItem: The cache item that was removed
• RemovedReason: The reason for removal (Removed, Expired, Evicted, ChangeMonitorChanged)

Common removal reasons:

• Removed: Item was explicitly removed
• Expired: Item expired (absolute or sliding expiration)
• Evicted: Item was evicted due to memory pressure
• ChangeMonitorChanged: Item was removed due to a dependency change

Practical callback examples

Cleanup resources:

var fileData = Cache.Get("FileData", "Files", 
    TimeSpan.FromMinutes(30), 
    CacheItemPriority.Default,
    () => LoadFileData("myfile.txt"),
    removedCallback: (args) =>
    {
        if (args.CacheItem.Value is IDisposable disposable)
        {
            disposable.Dispose();
        }
    });

Trigger dependent operations:

var config = Cache.Get("AppConfig", "Configuration", 
    DateTime.Now.AddHours(12), 
    () => LoadConfiguration(),
    removedCallback: (args) =>
    {
        // Refresh dependent services when configuration changes
        if (args.RemovedReason == CacheEntryRemovedReason.Expired)
        {
            RefreshDependentServices();
        }
    });

Cache dependencies

Set up dependencies between cache groups so that when one group is cleared, its dependent groups are also cleared:

// Set up dependencies
Cache.SetDependencies("ParentGroup", "ChildGroup1", "ChildGroup2");

// Now when ParentGroup is removed, ChildGroup1 and ChildGroup2 will also be removed
Cache.RemoveGroup("ParentGroup");

Cascading cache invalidation

// Set up dependencies
Cache.SetDependencies("UserData", "UserProfiles", "UserPreferences", "UserActivity");
Cache.SetDependencies("UserProfiles", "ProfilePhotos");

// Now when UserData is cleared, all dependent caches are also cleared
Cache.RemoveGroup("UserData");
// This will clear UserData, UserProfiles, ProfilePhotos, UserPreferences, and UserActivity

Best practices

1. Group related items: Use meaningful group names to organize related cache items.
2. Consider expiration strategies: Choose between sliding expiration (reset on access) and absolute expiration (fixed time) based on your use case.
3. Set dependencies: Use cache dependencies to maintain consistency between related data.
4. Use short keys: Keep your cache keys concise but descriptive.
5. Choose appropriate refresh intervals:
   • Balance data freshness needs with system resources
   • Use longer intervals for stable data, shorter for rapidly changing data
   • Consider the cost of your populate method when setting refresh frequency
   • Remember that refresh happens in background, so cache remains available
6. Use removal callbacks wisely:
   • Use callbacks for cleanup operations (disposing resources, closing connections)
   • Consider performance impact - callbacks are executed synchronously
   • Avoid heavy operations in callbacks to prevent blocking cache operations
   • Use callbacks for logging and monitoring cache behavior

Performance considerations

• The CacheUtility uses locks to ensure thread safety, but is designed to minimize lock contention.
• Populate methods are only called once per cache miss, even under high concurrency.
• Refresh operations are non-blocking: Cache calls return immediately with existing data, even during background refresh.
• Background refresh uses Task.Run() to prevent blocking the main thread.
• Multiple concurrent refresh requests for the same cache key are automatically deduplicated.
• Consider memory usage when caching large objects or collections.

When to use cache groups vs. key prefixes

• Cache groups: Use when you need to invalidate multiple related items at once.
• Key prefixes: Use within your keys when you want to organize items but may need more granular control.

Memory management

The CacheUtility is built on top of .NET's MemoryCache, which has built-in memory pressure detection. However, be mindful of:

• Setting appropriate cache priorities
• Using reasonable expiration times
• Caching only necessary data

Thread safety

All operations in CacheUtility are thread-safe. The implementation uses ReaderWriterLockSlim for efficient concurrent access and CacheLock for synchronizing modifications to the cache.