How do you implement a file-based cache system?

Question

ICSM Computer · Answer

Implementing a file-based cache system in C# allows you to store and retrieve data on disk efficiently, which is useful for scenarios like:
Caching API responsesStoring expensive computation resultsAvoiding redundant downloads or processing
Basic Structure
A simple file-based cache can:Use the filename as a key.Store serialized data (e.g., JSON or binary).Check timestamps or a TTL (time-to-live) to determine staleness.
Step-by-Step Implementation
using System;
using System.IO;
using System.Text.Json;
public class FileCache
{
    private readonly string _cacheDir;
    private readonly TimeSpan _defaultTtl;
    public FileCache(string cacheDir, TimeSpan? ttl = null)
    {
        _cacheDir = cacheDir;
        _defaultTtl = ttl ?? TimeSpan.FromMinutes(30);
        Directory.CreateDirectory(_cacheDir);
    }
    private string GetCachePath(string key)
    {
        string safeName = Convert.ToBase64String(System.Text.Encoding.UTF8.GetBytes(key));
        return Path.Combine(_cacheDir, safeName + ".json");
    }
    public void Setandlt;Tandgt;(string key, T value)
    {
        var path = GetCachePath(key);
        var cacheItem = new CacheItemandlt;Tandgt;
        {
            Timestamp = DateTime.UtcNow,
            Value = value
        };
        File.WriteAllText(path, JsonSerializer.Serialize(cacheItem));
    }
    public bool TryGetandlt;Tandgt;(string key, out T value)
    {
        var path = GetCachePath(key);
        value = default;
        if (!File.Exists(path))
            return false;
        try
        {
            var json = File.ReadAllText(path);
            var cacheItem = JsonSerializer.Deserializeandlt;CacheItemandlt;Tandgt;andgt;(json);
            if (DateTime.UtcNow - cacheItem.Timestamp andlt; _defaultTtl)
            {
                value = cacheItem.Value;
                return true;
            }
            else
            {
                File.Delete(path); // Cache expired
            }
        }
        catch
        {
            // corrupted cache file or deserialization failure
            File.Delete(path);
        }
        return false;
    }
    private class CacheItemandlt;Tandgt;
    {
        public DateTime Timestamp { get; set; }
        public T Value { get; set; }
    }
}
Usage Example
var cache = new FileCache("cache");
string key = "user_profile_123";
if (cache.TryGet(key, out string profileJson))
{
    Console.WriteLine("Cache hit: " + profileJson);
}
else
{
    // Simulate slow data fetch
    profileJson = "{ \"name\": \"John\" }";
    cache.Set(key, profileJson);
    Console.WriteLine("Cache miss. Data fetched and cached.");
}
Features You Can Add:
TTL per entryCustom serialization (binary or XML)Compression (e.g., GZip)Max file count or max total size limitCleanup policy (oldest files deleted when disk use is high)

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How do you implement a file-based cache system?

ICSM Computer

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1 Answers

Basic Structure

Step-by-Step Implementation

Usage Example

Features You Can Add:

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