Working with null values

What if a variable does not yet have a value? How can we indicate that? C# has the concept of a null value, which can be used to indicate that a variable has not been set.

If you are unsure of the difference between reference types and value types in .NET, then I recommend that you read the following online-only section before you continue with this section: https://github.com/markjprice/cs13net9/blob/main/docs/ch06-memory.md.

Making a value type nullable

By default, value types like int and DateTime must always have a value, hence their name. Sometimes, for example, when reading values stored in a database that allows empty, missing, or null values, it is convenient to allow a value type to be null. We call this a nullable value type.

You can enable this by adding a question mark as a suffix to the type when declaring a variable.

Let’s see an example. We will create a new project because some of the null handling options...