All that the line you posted does is copy the _reference_ from one
variable to another.  The reference refers to the same instance of the
Dictionary<>.

What you need is a method that will create a whole new instance of the
Dictionary<>.  I don't believe this is built into the Dictionary<> class
(some classes implement ICloneable, but Dictionary<> doesn't), but you
can easily do it yourself using the generic ICollection<>.CopyTo() method:

    Dictionary<string, myClass> Clone(Dictionary<string, myClass> dict)
    {
        KeyValuePair<string, myClass>[] rgkvp =
            new KeyValuePair<string, myClass>(dict.Count);
        Dictionary<string, myClass> dictNew = new Dictionary<string,
myClass>(dict.Count);

        dict.CopyTo(rgkvp, 0);

        foreach (KeyValuePair<string, myClass> kvp in rgkvp)
        {
            dictNew.Add(kvp.Key, kvp.Value);
        }

        return dictNew;
    }

Hope that helps.

Pete