Contrary to VO, many datatypes in the .NET Framework don't allow null values.

One of the most important ones is the DataTime class, that cannot have a null value, contrarily to VO, where a date variable can contain null_date.

In the .NET Framework there is the Nullable datatype, defined as follows:

Nullable<T>

and to be used like this:

local dDate as Nullable<DateTime>

dDate := null
dDate := DateTime.Now

Reference types in the .NET Framework don't need Nullable, they already support null values.

For more information see docs.microsoft.com/en-us/dotnet/csharp/programming-guide/nullable-types/