给IDistributedCache新增了扩展方法GetOrCreate、GetOrCreateAsync

public static class distributedcacheextensions
{
    public static titem getorcreate<titem>(this idistributedcache cache, string key, func<distributedcacheentryoptions, titem> factory)
    {
        titem t = default(titem);
        byte[] vs = cache.get(key);
        if (vs == null)
        {
            var options = new distributedcacheentryoptions();
            t = factory.invoke(options);
            cache.set(key, messagepack.messagepackserializer.serialize<titem>(t), options);
        }
        else
        {
            t = messagepack.messagepackserializer.deserialize<titem>(vs);
        }

        return t;
    }

    public static async task<titem> getorcreateasync<titem>(this idistributedcache cache, string key, func<distributedcacheentryoptions, task<titem>> factory)
    {
        titem t = default(titem);
        byte[] vs = cache.get(key);
        if (vs == null)
        {
            var options = new distributedcacheentryoptions();
            t = await factory.invoke(options);
            await cache.setasync(key, messagepack.messagepackserializer.serialize<titem>(t), options);
        }
        else
        {
            t = messagepack.messagepackserializer.deserialize<titem>(vs);
        }

        return t;
    }
}

user user = _distributedcache.getorcreate("key", (options) =>
{
    options.absoluteexpirationrelativetonow = timespan.fromseconds(20);

    return new user
    {
        id = 1,
        name = "bidianqing"
    };
});

[datacontract]
public class user
{
    [datamember(order =0)]
    public int id { get; set; }

    [datamember(order = 1)]
    public string name { get; set; }
}

install-package messagepack