c# - Is it possible to create a method that returns one of two possible types? -

c# - Is it possible to create a method that returns one of two possible types? -

i have 2 info structures: dictionary<string, string> , multimap<string, string>. multimap dictionary under hood. took must of code this question. here's class definition:

public class multimap<tkey, tvalue> : dictionary<tkey, hashset<tvalue>> { ... }

both info structures have .add(tkey key, tvalue value) method.

i have class responsible populating these maps files. have next 2 methods:

public dictionary<string, string> populatedictionary(...) { dictionary<string, string> returndictionary = new dictionary<string, string>(); ... foreach (...) { ... returndictionary.add(key, value); } homecoming returndictionary; } public multimap<string, string> populatemultimap(...) { multimap<string, string> returnmultimap = new multimap<string, string>(); ... foreach (...) { ... returnmultimap.add(key, value); } homecoming returnmultimap; }

as can see, they're same, both around 25 lines long, , difference homecoming type. looking condense 1 method. first effort have method

public dictionary<string, object> populategenericdictionary(...) { ... }

where object either string or hashset<string>. didn't have much luck casting dictionary<string, object> multimap<string, string>.

extracting logic out of methods option, it's not great. because of foreach loops, there's going logic within 2 methods. end methods twice small, there's still 2 identical methods, doesn't solve problem.

this ideal method structure:

public dictionary<string, string> populatedictionary(...) { homecoming methodthatdoesallthelogic(...); } public multimap<string, string> populatemultimap(...) { homecoming methodthatdoesallthelogic(...); } public ??? methodthatdoesallthelogic(...) { ... }

i've been fiddling around casting , generics, can't work. ideas?

edit

i have used millimoose's solution. here's code now:

public dictionary<string, string> generatedictionary(...) { dictionary<string, string> returnmap = new dictionary<string, string>(); populatedictionary(returnmap.add, ...); homecoming returnmap; } public multimap<string, string> generatemultimap(...) { multimap<string, string> returnmap = new multimap<string, string>(); populatedictionary(returnmap.add, ...); homecoming returnmap; } private static void populategenericdictionary(action<string, string> addfunc, ...) { ... foreach (...) { addfunc(key, value); } }

much cleaner!

to work around lack of mutual interface, can invent 1 ad-hoc using bunch of delegate type parameters:

void methodthatdoesallthelogic(action<string, string> addfunc) { // ... addfunc(key, value); // ... } public dictionary<...> populatedictionary() { // ... methodthatdoesallthelogic(result.add); }

(adding more parameters necessary.)

c# generics dictionary casting