Variable declaration question mark

I was looking at so开发者_如何学JAVAme existing code and stumbled across a variable declaration I didn't understand:

public foo as Boolean?

What does the question mark signify?

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It means a nullable Boolean.

Boolean?, or any other value type (number or struct), is shorthand for Nullable(Of Boolean).

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aah, no sooner did I post the question that I realised that it may signify that it can be nullable.

I tested in code and that seems to be the case.