public KeyValuePair <StateItemKey, Object> Add(Type type, string key, object value)
{
if (Contains(type, key))
{
throw new ArgumentException("Same type+key exists.");
}
var stateKey = new StateItemKey(type, key);
Add(stateKey.ToString(), value);
var item = new KeyValuePair <StateItemKey, object>(stateKey, value);
return(item);
}
public bool Contains(StateItemKey key) => ContainsKey(key.ToString());