return types

Question

is this type of thing ok.

namespace myclass
{
        class set
        {
        List<object> mList
        //constructors and stuff

        public set union(set passedSet)
        {
                set tempSet = new set();
                        //do stuff
                return tempSet;
        }
        
        }
    
}

Basically I have a class library and the methods in that library need to return the type that the class its self is building.  Is that ok.  When I worte it the word set turned light blue - so I though every thing cool.  Now that im using the class library the words set have tured black and im getting data type eror when values are passes to methods etc.