Visual Basic 2015 Unleashed

Introducing Nullable Types

As you read in the discussion of value types and reference types, value types have a default value that is zero, whereas reference types have a default value that is a null reference and is represented in VB by the Nothing language literal. This is because a reference type can store null values, but value types cannot. Attempting to assign a null value to a value type would result in resetting to the default value for that type. This is a limitation because there are situations in which you need to store null values in value types, such as when fetching data from a SQL Server database. You can have a hypothetical Orders table where the Ship date column enables null values. SQL Server has its own data types, one of ...