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Asked: 2026-05-10T15:00:25+00:00

I am reading a .NET book, and in one of the code examples there

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I am reading a .NET book, and in one of the code examples there is a class definition with this field:

private DateTime? startdate

What does DateTime? mean?

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  1. Since DateTime is a struct, not a class, you get a DateTime object, not a reference, when you declare a field or variable of that type.

    And, in the same way as an int cannot be null, so this DateTime object can never be null, because it’s not a reference.

    Adding the question mark turns it into a nullable type, which means that either it is a DateTime object, or it is null.

    DateTime? is syntactic sugar for Nullable<DateTime>, where Nullable is itself a struct.

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