Asp.net Core 改变了之前的封闭，现在开源且开放，下面我们来用Redis存储Session来做一个简单的测试，或者叫做中间件（middleware）。
对于Session来说褒贬不一，很多人直接说不要用，也有很多人在用，这个也没有绝对的这义，个人认为只要不影什么且又可以方便实现的东西是可以用的，现在不对可不可用做表态，我们只关心实现。
类库引用
这个相对于之前的.net是方便了不少，需要在project.json中的dependencies节点中添加如下内容：
"StackExchange.Redis": "1.1.604-alpha", "Microsoft.AspNetCore.Session": "1.1.0-alpha1-21694"
Redis实现
这里并非我实现，而是借用不知道为什么之前还有这个类库，而现在NUGET止没有了，为了不影响日后升级我的命名空间也用 Microsoft.Extensions.Caching.Redis
可以看到微软这里有四个类，其实我们只需要三个，第四个拿过来反而会出错：
using System; using System.Threading.Tasks; using Microsoft.Extensions.Caching.Distributed; using Microsoft.Extensions.Options; using StackExchange.Redis; namespace Microsoft.Extensions.Caching.Redis { public class RedisCache : IDistributedCache, IDisposable { // KEYS[1] = = key // ARGV[1] = absolute-expiration - ticks as long (-1 for none) // ARGV[2] = sliding-expiration - ticks as long (-1 for none) // ARGV[3] = relative-expiration (long, in seconds, -1 for none) - Min(absolute-expiration - Now, sliding-expiration) // ARGV[4] = data - byte[] // this order should not change LUA script depends on it private const string SetScript = (@" redis.call('HMSET', KEYS[1], 'absexp', ARGV[1], 'sldexp', ARGV[2], 'data', ARGV[4]) if ARGV[3] ~= '-1' then redis.call('EXPIRE', KEYS[1], ARGV[3]) end return 1"); private const string AbsoluteExpirationKey = "absexp"; private const string SlidingExpirationKey = "sldexp"; private const string DataKey = "data"; private const long NotPresent = -1; private ConnectionMultiplexer _connection; private IDatabase _cache; private readonly RedisCacheOptions _options; private readonly string _instance; public RedisCache(IOptions<RedisCacheOptions> optionsAccessor) { if (optionsAccessor == null) { throw new ArgumentNullException(nameof(optionsAccessor)); } _options = optionsAccessor.Value; // This allows partitioning a single backend cache for use with multiple apps/services. _instance = _options.InstanceName ?? string.Empty; } public byte[] Get(string key) { if (key == null) { throw new ArgumentNullException(nameof(key)); } return GetAndRefresh(key, getData: true); } public async Task<byte[]> GetAsync(string key) { if (key == null) { throw new ArgumentNullException(nameof(key)); } return await GetAndRefreshAsync(key, getData: true); } public void Set(string key, byte[] value, DistributedCacheEntryOptions options) { if (key == null) { throw new ArgumentNullException(nameof(key)); } if (value == null) { throw new ArgumentNullException(nameof(value)); } if (options == null) { throw new ArgumentNullException(nameof(options)); } Connect(); var creationTime = DateTimeOffset.UtcNow; var absoluteExpiration = GetAbsoluteExpiration(creationTime, options); var result = _cache.ScriptEvaluate(SetScript, new RedisKey[] { _instance + key }, new RedisValue[] { absoluteExpiration?.Ticks ?? NotPresent, options.SlidingExpiration?.Ticks ?? NotPresent, GetExpirationInSeconds(creationTime, absoluteExpiration, options) ?? NotPresent, value }); } public async Task SetAsync(string key, byte[] value, DistributedCacheEntryOptions options) { if (key == null) { throw new ArgumentNullException(nameof(key)); } if (value == null) { throw new ArgumentNullException(nameof(value)); } if (options == null) { throw new ArgumentNullException(nameof(options)); } await ConnectAsync(); var creationTime = DateTimeOffset.UtcNow; var absoluteExpiration = GetAbsoluteExpiration(creationTime, options); await _cache.ScriptEvaluateAsync(SetScript, new RedisKey[] { _instance + key }, new RedisValue[] { absoluteExpiration?.Ticks ?? NotPresent, options.SlidingExpiration?.Ticks ?? NotPresent, GetExpirationInSeconds(creationTime, absoluteExpiration, options) ?? NotPresent, value }); } public void Refresh(string key) { if (key == null) { throw new ArgumentNullException(nameof(key)); } GetAndRefresh(key, getData: false); } public async Task RefreshAsync(string key) { if (key == null) { throw new ArgumentNullException(nameof(key)); } await GetAndRefreshAsync(key, getData: false); } private void Connect() { if (_connection == null) { _connection = ConnectionMultiplexer.Connect(_options.Configuration); _cache = _connection.GetDatabase(); } } private async Task ConnectAsync() { if (_connection == null) { _connection = await ConnectionMultiplexer.ConnectAsync(_options.Configuration); _cache = _connection.GetDatabase(); } } private byte[] GetAndRefresh(string key, bool getData) { if (key == null) { throw new ArgumentNullException(nameof(key)); } Connect(); // This also resets the LRU status as desired. // TODO: Can this be done in one operation on the server side? Probably, the trick would just be the DateTimeOffset math. RedisValue[] results; if (getData) { results = _cache.HashMemberGet(_instance + key, AbsoluteExpirationKey, SlidingExpirationKey, DataKey); } else { results = _cache.HashMemberGet(_instance + key, AbsoluteExpirationKey, SlidingExpirationKey); } // TODO: Error handling if (results.Length >= 2) { // Note we always get back two results, even if they are all null. // These operations will no-op in the null scenario. DateTimeOffset? absExpr; TimeSpan? sldExpr; MapMetadata(results, out absExpr, out sldExpr); Refresh(key, absExpr, sldExpr); } if (results.Length >= 3 && results[2].HasValue) { return results[2]; } return null; } private async Task<byte[]> GetAndRefreshAsync(string key, bool getData) { if (key == null) { throw new ArgumentNullException(nameof(key)); } await ConnectAsync(); // This also resets the LRU status as desired. // TODO: Can this be done in one operation on the server side? Probably, the trick would just be the DateTimeOffset math. RedisValue[] results; if (getData) { results = await _cache.HashMemberGetAsync(_instance + key, AbsoluteExpirationKey, SlidingExpirationKey, DataKey); } else { results = await _cache.HashMemberGetAsync(_instance + key, AbsoluteExpirationKey, SlidingExpirationKey); } // TODO: Error handling if (results.Length >= 2) { // Note we always get back two results, even if they are all null. // These operations will no-op in the null scenario. DateTimeOffset? absExpr; TimeSpan? sldExpr; MapMetadata(results, out absExpr, out sldExpr); await RefreshAsync(key, absExpr, sldExpr); } if (results.Length >= 3 && results[2].HasValue) { return results[2]; } return null; } public void Remove(string key) { if (key == null) { throw new ArgumentNullException(nameof(key)); } Connect(); _cache.KeyDelete(_instance + key); // TODO: Error handling } public async Task RemoveAsync(string key) { if (key == null) { throw new ArgumentNullException(nameof(key)); } await ConnectAsync(); await _cache.KeyDeleteAsync(_instance + key); // TODO: Error handling } private void MapMetadata(RedisValue[] results, out DateTimeOffset? absoluteExpiration, out TimeSpan? slidingExpiration) { absoluteExpiration = null; slidingExpiration = null; var absoluteExpirationTicks = (long?)results[0]; if (absoluteExpirationTicks.HasValue && absoluteExpirationTicks.Value != NotPresent) { absoluteExpiration = new DateTimeOffset(absoluteExpirationTicks.Value, TimeSpan.Zero); } var slidingExpirationTicks = (long?)results[1]; if (slidingExpirationTicks.HasValue && slidingExpirationTicks.Value != NotPresent) { slidingExpiration = new TimeSpan(slidingExpirationTicks.Value); } } private void Refresh(string key, DateTimeOffset? absExpr, TimeSpan? sldExpr) { if (key == null) { throw new ArgumentNullException(nameof(key)); } // Note Refresh has no effect if there is just an absolute expiration (or neither). TimeSpan? expr = null; if (sldExpr.HasValue) { if (absExpr.HasValue) { var relExpr = absExpr.Value - DateTimeOffset.Now; expr = relExpr <= sldExpr.Value ? relExpr : sldExpr; } else { expr = sldExpr; } _cache.KeyExpire(_instance + key, expr); // TODO: Error handling } } private async Task RefreshAsync(string key, DateTimeOffset? absExpr, TimeSpan? sldExpr) { if (key == null) { throw new ArgumentNullException(nameof(key)); } // Note Refresh has no effect if there is just an absolute expiration (or neither). TimeSpan? expr = null; if (sldExpr.HasValue) { if (absExpr.HasValue) { var relExpr = absExpr.Value - DateTimeOffset.Now; expr = relExpr <= sldExpr.Value ? relExpr : sldExpr; } else { expr = sldExpr; } await _cache.KeyExpireAsync(_instance + key, expr); // TODO: Error handling } } private static long? GetExpirationInSeconds(DateTimeOffset creationTime, DateTimeOffset? absoluteExpiration, DistributedCacheEntryOptions options) { if (absoluteExpiration.HasValue && options.SlidingExpiration.HasValue) { return (long)Math.Min( (absoluteExpiration.Value - creationTime).TotalSeconds, options.SlidingExpiration.Value.TotalSeconds); } else if (absoluteExpiration.HasValue) { return (long)(absoluteExpiration.Value - creationTime).TotalSeconds; } else if (options.SlidingExpiration.HasValue) { return (long)options.SlidingExpiration.Value.TotalSeconds; } return null; } private static DateTimeOffset? GetAbsoluteExpiration(DateTimeOffset creationTime, DistributedCacheEntryOptions options) { if (options.AbsoluteExpiration.HasValue && options.AbsoluteExpiration <= creationTime) { throw new ArgumentOutOfRangeException( nameof(DistributedCacheEntryOptions.AbsoluteExpiration), options.AbsoluteExpiration.Value, "The absolute expiration value must be in the future."); } var absoluteExpiration = options.AbsoluteExpiration; if (options.AbsoluteExpirationRelativeToNow.HasValue) { absoluteExpiration = creationTime + options.AbsoluteExpirationRelativeToNow; } return absoluteExpiration; } public void Dispose() { if (_connection != null) { _connection.Close(); } } } }