How can I delete cache entries by key prefix using built-in hybrid caching in ASP.NET Core 9?
What is the best way to implement prefix-based deletion of cached keys using only the built-in caching packages (without third-party libraries like Ziggurat or EasyCaching)?
Example:
Let’s say I have cached multiple items with the following keys:
"user-picture-1","user-picture-2","user-info-1",...
I want to remove only the cache entries whose keys start with "user-picture-", so that it deletes:
"user-picture-1","user-picture-2"
and does not delete other entries like "user-info-1".
Answer
ASP.NET Core's built-in caching mechanisms (MemoryCache and DistributedCache) do not natively support deletion by key prefix. This is by design — both cache implementations treat keys as opaque strings and lack built-in enumeration or prefix-based operations for performance and scalability reasons.
However, you can implement prefix-based deletion yourself by maintaining a key index or using a naming/versioning pattern.
public class CacheManager
{
private readonly IMemoryCache _cache;
private readonly Dictionary<string, HashSet<string>> _prefixIndex = new();
public CacheManager(IMemoryCache cache)
{
_cache = cache;
}
public void Set<T>(string key, T value, string prefix, TimeSpan? expiration = null)
{
// Add to cache
var options = new MemoryCacheEntryOptions();
if (expiration.HasValue)
{
options.SetAbsoluteExpiration(expiration.Value);
}
_cache.Set(key, value, options);
// Track key in index
if (!_prefixIndex.ContainsKey(prefix))
{
_prefixIndex[prefix] = new HashSet<string>();
}
_prefixIndex[prefix].Add(key);
}
public T? Get<T>(string key)
{
return _cache.TryGetValue(key, out T value) ? value : default;
}
public void RemoveByPrefix(string prefix)
{
if (_prefixIndex.TryGetValue(prefix, out var keys))
{
foreach (var key in keys)
{
_cache.Remove(key);
}
_prefixIndex.Remove(prefix);
}
}
}