Nullable Bool and Radiobuttons in ASP.NET MVC

It’s quite common to have Yes/No answers in a form. What’s the best way to represent these? Well, a binary answer like that maps best to a boolean, right? True, but what about null?

There’s two possible ways in which we might use a null. It could represent a N/A or Don’t Care response to the question. I don’t think this is a valid use of null however. Null should mean there is literally no value for this yet. So if we view this field in the DB, and we see a null, we can take it to read ‘this has not been answered’.

So if we want a N/A option, I don’t think we should be using a bool. We should have an enumerated type of some kind at this point.

OK so what input element do we use? Maybe a checkbox. Well, this only gives us two possible scenarios – checked and unchecked. And we have no way of differentiating between unchecked and null. If the checkbox is unchecked, is that because the user wants to select false, or is it because they simply haven’t answered this question yet?

So we can use radio buttons. One radio for yes, one for no. And if the user hasn’t answered the question yet, then neither yes or no is checked. we have a nullable bool? Because the response to something may currently be unanswered. We can’t assume that because it is null that that means true or false.

One possible option is to have 3 radio options – one meaning yes, one meaning no, and one meaning something like N/A or Don’t Care.

It might work in some cases (what cases?), but in our case, N/A or Don’t Care is not a valid answer. Null means this question has not yet been answered.

Does null mean a 3rd option, such as N/A? No, it means unanswered. So we don’t want a 3rd option.

What we want is Yes and No radio buttons, and then for neither of them to be selected if the user has currently not answered.

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