source: TFP-WebServer/WebServer/src/FileCache/SimpleCache.cs@ 499

using System;
using System.Collections.Generic;
using System.IO;

namespace Webserver.FileCache {
        // Caching all files, useful for completely static folders only
        public class SimpleCache : AbstractCache {
                private readonly Dictionary<string, byte[]> fileCache = new Dictionary<string, byte[]> ();

                public override byte[] GetFileContent (string _filename) {
                        try {
                                lock (fileCache) {
                                        if (fileCache.TryGetValue(_filename, out byte[] content)) {
                                                return content;
                                        }

                                        if (!File.Exists (_filename)) {
                                                return null;
                                        }

                                        byte[] newContent = File.ReadAllBytes (_filename);
                                        fileCache.Add (_filename, newContent);

                                        return newContent;
                                }
                        } catch (Exception e) {
                                Log.Out ($"Error in SimpleCache.GetFileContent: {e}");
                        }

                        return null;
                }

                public override (int, int) Invalidate () {
                        (int, int) result = (0, 0);
                        
                        lock (fileCache) {
                                result.Item1 = fileCache.Count;
                                foreach ((string _, byte[] data) in fileCache) {
                                        result.Item2 += data.Length;
                                }
                                
                                fileCache.Clear ();
                        }

                        return result;
                }
        }
}