CacheUtility 1.0.10

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

Basic Usage

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

using CacheUtility;

Retrieving or Creating Cached Items

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();
});

// 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();
});

// With full customization
var result = Cache.Get("MyKey", "MyGroupName", 
    DateTime.Now.AddDays(1), // Absolute expiration
    TimeSpan.FromMinutes(10), // Sliding expiration
    CacheItemPriority.Default, // Priority
    () => MyLongRunningTask());

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");

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"

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" });

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), // Absolute expiration
    TimeSpan.FromMinutes(10), // Or use 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();
        }
    });

Advanced Features

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");

Practical 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();
});

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}");
}

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. 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.
• 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.