Redis HashKey erroring out

Redis HashKey erroring out

I created a HaskKey using Boolsleve c#, i am providing a unique field each
time and my item is Json string.
public virtual void AddHashSetKey(string item, string hashField)
{
_redisClient.Hashes.Set(_database, Key, hashField, item);
}
After adding about thousands fields (141988) i try to check the number of
fields in the hash key but get error below. not sure where i can find more
details or why am i getting this error?
redis 127.0.0.1:6379[1]> Exists C:
(integer) 1
redis 127.0.0.1:6379[1]> HLEN C:
(error) ERR Operation against a key holding the wrong kind of value
redis 127.0.0.1:6379[1]>