Question

I’m trying to store IEnumerable<T> into memcached, however, I have only been able to successfully store only an instance of T.

Is there different code for storing an enumeration in memcached?

public IEnumerable<UsContentView> GetContentViewByUserId(int userId)
    {
        Expire("contentViewUserId_" + userId);
        var result = Memcached.Get<IEnumerable<UsContentView>>("contentViewUserId_" + userId);

        if (result == null)
        {
            result = db.UsContentViews.Where(m => m.UserID == userId).OrderBy(m => m.ArticleId).Distinct();

            var arr = result.ToArray();
            var arrList = arr.ToList();
            //store it in the cache, with the key
            StoreList(arrList, "contentViewUserId_" + userId);

            MemoryStream mem = new MemoryStream();
            BinaryFormatter b = new BinaryFormatter();
            try
            {
                b.Serialize(mem, result);
            }
            catch (EntitySqlException ex)
            {
                throw new ApplicationException("The object query failed", ex);
            }
            catch (EntityCommandExecutionException ex)
            {
                throw new ApplicationException("The object query failed", ex);
            }
            catch (SerializationException ex)
            {
                throw new ApplicationException("The object graph could not be serialized", ex);
            }
        }

        return result;
    }

Answer 1

Resolve it to an array or list and store in the same manner as T.

using System.Linq;

var array = myEnumerable.ToArray();
var list = myEnumerable.ToList();

With lists of things, be careful not to hit the 2MB per key in-memory maximum on Memcached, 10MB if you have disk-backing enabled for keys.

We actually get around this by storing byte[] and using custom serialization (sometimes home-brew, sometimes ProtoBuf) to keep things speedy and light.