Question

dim val1 As Integer? = If(5 > 2, Nothing, 43)
' val1 = 0

dim val1 As Integer? = If(5 > 2, Nothing, Nothing)
' val1 = Nothing

What gives? Is this a bug, or am I overlooking something?

Answer 1

The problem is that Nothing in VB.NET works differently than, for example, null in C#. When Nothing is used in the context of a value type (such as Integer) it represents the default value of that type. In this case, that’s 0.

In your first example, both branches of the ternary operator are valid Integer values. The true branch represents 0 and the false branch represents 43.

In the second example, neither branch of the ternary operator is a valid Integer value, thus forcing the VB.NET compiler to assume that the overall operator returns Object, not Integer.

To make the first example work the way you intend, you need to make it clear to the compiler that the ternary operator should resolve to an Integer?, not an Integer or an Object. You can do so like this:

dim val1 As Integer? = If(5 > 2, Nothing, New Integer?(43))

By explicitly making the false branch of the operator an Integer?, the Nothing in the true branch will represent the null value, instead of the default Integer value.