非 atomic

DistributedCacheExtensions.cs

    public static class DistributedCacheExtensions {

        public static async Task<T> GetOrSetAsync<T>(this IDistributedCache cache
            , string key
            , Func<byte[], T> deserialize
            , Func<Task<(T, byte[], DistributedCacheEntryOptions options)>> factory
            , CancellationToken token = default
        ) {
            if (cache is null) { throw new ArgumentNullException(nameof(cache)); }
            if (key is null) { throw new ArgumentNullException(nameof(key)); }
            if (deserialize is null) { throw new ArgumentNullException(nameof(deserialize)); }
            if (factory is null) { throw new ArgumentNullException(nameof(factory)); }

            byte[]? value = await cache.GetAsync(key, token).ConfigureAwait(false);
            if (value is { }) {
                return deserialize(value);
            }

            (T result, value, DistributedCacheEntryOptions options) = await factory().ConfigureAwait(false);
            if (options is null) {
                await cache.SetAsync(key, value, token).ConfigureAwait(false);
            }
            else {
                await cache.SetAsync(key, value, options, token).ConfigureAwait(false);
            }
            return result;
        }
    }