Coding practices for C# Nullable type

Question

I have never used nullable types in my C# code. Now I have decided to change my coding practice by introducing nullable types in my code.

What are the major changes in the coding practices should be made while making a transition from normal datatypes to nullable data-types in case of application programming?

What are the areas that should be taken care of?

What are the points I should always watch out for?

Answer 1

Don't use nullable types because they are a "cool new thing" you have discovered. Use them where they are applicable and genuinely useful.

There are overheads to using them, and if used incorrectly they will unnecessarily increase the complexity of your code.

You also have to be careful to avoid null dereferences, so they place additonal burden on programmers working with that code. (In some cases this is preferable to the cost of a workaround approach though!)

Answer 2

This good article should help you.

Answer 3

I rarely use nullable types. The only place I've use them is when I'm dealing with null types in the database.

Answer 4

Nullable<T> is useful for when you need a possible invalid state for a value type, or if the data is being retrieved from a database that may contain a null value for the column. It is very common in some old FORTRAN code I am porting to C# for invalid values to be negative or 0, but this is troublesome especially when the values are used in mathematical functions. It is far more explicit to use Nullable<T> to show that possible invalid state.

It is worth mentioning that the following is the same:

Nullable<int> myNullableInt;
int? myNullableInt;

Answer 5

A couple of other good ideas for using nullable types:

• Don't forget the flexibility in syntax. Nullable<int> is the same as int?
• Check for null (var.HasValue) and cast it to base type before using it as the base type.

Answer 6

They seem suitable for the starting value of some value type variables.

int? lastCodeReceived;

if (lastCodeReceived.HasValue)
{
    // At least one code has been received.
}