Handling nullable value types in .NET 1.x

One of the great new features in .NET 2.0 is support for nullable types, especially important when dealing with value types such as Int or DateTime values coming from a database. Previously you were forced to either set and track another binary flag or to use a “special” value to represent null that sooner or later would turn up in real data.

In C# 2.0 thanks to a bit of syntactic sugar we can do this;

int? nullable1 = 1;
if (nullable1 == null) nullable1 = 2;

Which the C# compiler actually turns into the following:

Nullable<int> nullable1 = new Nullable<int>(1);
if (!nullable1.HasValue) nullable1 = new Nullable<int>(2);

This makes use of the new Nullable<T> generic structure to wrap the value with an additional boolean HasValue property.

That looks surprisingly similar to the syntax of the open-source NullableTypes project you can use with .NET 1.1 (or 2.0):

NullableInt32 nullable1 = new NullableInt32(1);
if (nullable1.IsNull) nullable1 = new NullableInt(2);

Disclaimer: I’ve worked on the NullableTypes project specifically implementing the IXmlSerializable, NullableGuid & NullableTimeSpan.

[)amien