C#•2y ago

✅ When calling a generic function, how can I tell it that I'm going to be passing null?

I've got a generic function which is something like this:

public ReturnType GetValue<ReturnType, ContentType>(ContentType content);

public ReturnType GetValue<ReturnType, ContentType>(ContentType content);

I always want to call it with a ReturnType specified, but sometimes I want to pass in null as the content. How can I call this to say that I want to pass in null? Ideally, I'd like to be able to do something like this:

string result = GetValue<string, NullType>(null);

string result = GetValue<string, NullType>(null);

Or even:

string result = GetValue<string, NullType>();

string result = GetValue<string, NullType>();

This second one is possible if I pick any type as the second generic type and change the function definition to this

public ReturnType GetValue<ReturnType, ContentType>(ContentType? content = null);

public ReturnType GetValue<ReturnType, ContentType>(ContentType? content = null);

However, I don't like putting a valid type in there if that's not what I mean, as that will be confusing to future developers (including future myself) Thanks

2 Replies

ero•2y ago

you need to specify multiple overloads for that, i think. passing in null isn't exactly a good pattern (at least in my opinion) for that, i'd just have a second, empty overload

public TReturn GetValue<TContent, TReturn>(TContent? content);
public TReturn GetValue<TReturn>();

public TReturn GetValue<TContent, TReturn>(TContent? content);
public TReturn GetValue<TReturn>();

HughOP•2y ago

Thanks - that's really helpful - I didn't realise that I could do overloads like that

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✅ When calling a generic function, how can I tell it that I'm going to be passing null?