StackExchange.Redis - How to add items to a Redis Set

Question

I'm trying to achieve the following scenarios:

1. Add 5 items of type T to a new Redis SET
2. Add 1 item of type T to an existing Redis SET

(i know SETADD doesn't care if the set is existing, but just listing my scenarios for reference)

I can see there is SetAddAsync(RedisKey, RedisValue value) and SetAddAsync(RedisKey, RedisValue[] values), but i'm not sure how to work with it (and which overload to use?)

When i've used StringSet, i simply serialize T to a byte[], then use that as the RedisValue param.

But not sure how to do it for sets.

This is what i have:

var items = values.Select(serializer.Serialize).ToArray();
await cache.SetAddAsync(key, items);

where serializer is a class which converts T to a byte[]

Answer 1

It is basically identical to how you would use StringSet. The only difference is that when setting a string, it only makes sense to set one value - but when adding to a set, you might want to add 1 or more elements at a time.

If you're adding one element, just use:

db.SetAdd[Async](key, serializedValue);

If you want to add a larger number of items to the set in one go, then first get the serialized items, for example:

var items = Array.ConvertAll(values, value => (RedisValue)serializer.Serialize(value));

or to tweak your existing code:

var items = values.Select(value => (RedisValue)serializer.Serialize(value)).ToArray();

The important difference here is that I expect your original code is ending up with a byte[][], where-as you need a RedisValue[]. The (RedisValue) cast in the above should fix that for you.

Then call:

db.SetAdd[Async](key, serializedValues);

This corresponds to the variadic form of SADD.