Mastering NullReferenceException Prevention in C#/

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C# 6.0-8.0 Nullable Operators

Use nullable operators to simplify null checks.

We'll cover the following...

Without nullable operators
With nullable operators

So far, we covered that to avoid the NullReferenceException:

We should check for null before accessing the methods or properties of an object.
We should reject null from our methods when they require some parameters.

Let’s look at the new operators C# introduced to simplify our null checks: ?., ??, and ??=. These operators don’t prevent us from having null in the first place, but they help us simplify our work of checking for null values.

Without nullable operators

Let’s start with an example and refactor it to use these new operators.

Let’s say we want to find one movie from our catalog to follow its director.

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main.cs

NRE.csproj

string name = null;
var movie = FindMovie();
if (movie == null
    || movie.Director == null
    || movie.Director.Name == null)
{
    name = "Steven Spielberg";
}
else
{
    name = movie.Director.Name;
}
Console.WriteLine($"Follow: {name}");
static Movie FindMovie()
{
    // Imagine this is a database call that might
    // or might not return a movie
    var lordOfTheRings = new Movie("The Lord of the Rings: The Two Towers", 2002, 8.8f)
    {
        Director = new Director("Peter Jackson", new DateTime(1961, 10, 31))
    };
    // To add some randomness and emulate a database call
    // without results
    var random = new Random();
    var bit = random.NextDouble();
    return (bit >= 0.5) ? null : lordOfTheRings;
}
record Movie(string Name, int ReleaseYear, float Rating)
{
    public Director Director { get; set; }
}
record Director(string Name, DateTime BirthDate);