如何在Linq to SQL中实现缓存？

using System.Runtime.Caching;

public class DataContext : System.Data.Linq.DataContext
{
    private static readonly MemoryCache Cache = MemoryCache.Default;

    public DataContext(string connectionString) : base(connectionString) { }

    public override object GetChangeTrackingToken(object entity)
    {
        var key = GetCacheKey(entity);
        var token = Cache.Get(key);
        if (token == null)
        {
            token = base.GetChangeTrackingToken(entity);
            Cache.Add(key, token, new CacheItemPolicy { AbsoluteExpiration = DateTimeOffset.Now.AddMinutes(1) });
        }
        return token;
    }

    private string GetCacheKey(object entity)
    {
        return $"{entity.GetType().FullName}:{entity.GetHashCode()}";
    }
}