Why is .NET's Version a class and not a struct?

Question

According to ReferenceSource, the Version class is sealed, ICloneable, IComparable, IComparable<Version>, IEquatable<Version>. It also only stores int values. Is there a particular reason why the .NET programmers chose to make this a class instead of a struct? Why would someone need a null version?

Here's the field declaration block from ReferenceSource:

// AssemblyName depends on the order staying the same
private int _Major;
private int _Minor;
private int _Build = -1;
private int _Revision = -1;

They even make a comment, saying they need to keep the fields aligned. Maybe it's just me, but this is really a struct thing?

The difference between a `struct` and a `class` is more than simply allowing a `null` value... — Willem Van Onsem, Jan 09 '16 at 18:36
@WillemVanOnsem The OP clearly knows this, hence all the details mentioned in the question, which are indeed intended to make this class behave mostly like a value. — Konrad Rudolph, Jan 09 '16 at 18:37
@WillemVanOnsem I know, but that's the only use I could think of it as a class instead of a struct... — Philippe Paré, Jan 09 '16 at 18:37
@KonradRudolph that's basically it. I feel it should behave like a value... — Philippe Paré, Jan 09 '16 at 18:38
Related: http://stackoverflow.com/questions/521298/when-to-use-struct — Caramiriel, Jan 09 '16 at 18:42

score 5 · Accepted Answer · answered Jan 09 '16 at 18:32

Why would someone need a null version?

To specify that no version is specified, for instance in AssemblyName as referred to in the comment in your question. An AssemblyName may omit the version when passed to Assembly.Load, for instance, in which case its Version property will be null. Remember that these types were created for .NET 1.0, which didn't have generics, so Nullable<Version> didn't exist yet as an alternative.

Why is .NET's Version a class and not a struct?

1 Answers1