The default scope of a Class, Property, Field, Method is private, so you'll need to tell the compiler that the method is public by writing
public
before your method declaration e.g.
public void MyMethod{ }
If you have implemented the .NET interface
IDictionary<TKey, TValue>[
^] then your code wont even compile if the methods and properties aren't public as the interface is public and thus so must the methods and properties.