.net - Nullable type and if issue

Question

Here is simplest piece of code

Dim testInvoiceDate As DateTime? = If(String.IsNullOrEmpty(Nothing),
                                      Nothing,
                                      New DateTime(2018, 3, 20))

Why variable testInvoiceDate is not Nothing , but #1/1/0001 12:00:00 AM# ?! That is very weird !

Answer 1

The If-statement will return the same datatype for both cases.
Because the return-type in the False-case is DateTime, the return-type is the DateTime-default-value for the True-case.

Default for DateTime is DateTime.MinValue which is #1/1/0001 12:00:00 AM#.

This will work as expected:

Dim testInvoiceDate As DateTime? = If(String.IsNullOrEmpty(Nothing),
                                      Nothing,
                                      New DateTime?(New Date(2018, 3, 20)))