rspec/rules/S3655/csharp/rule.adoc

== Why is this an issue?

https://learn.microsoft.com/en-us/dotnet/api/system.nullable-1[Nullable value types] can hold either a value or `null`.

The value held in the nullable type can be accessed with the `Value` property or by casting it to the underlying type. Still, both operations throw an `InvalidOperationException` when the value is `null`. A nullable type should always be tested before accessing the value to avoid raising exceptions.

== How to fix it

=== Code examples

==== Noncompliant code example

[source,csharp,diff-id=1,diff-type=noncompliant]
----
void Sample(bool condition)
{
    int? nullableValue = condition ? 42 : null;
    Console.WriteLine(nullableValue.Value); // Noncompliant: InvalidOperationException is raised

    int? nullableCast = condition ? 42 : null;
    Console.WriteLine((int)nullableCast);   // Noncompliant: InvalidOperationException is raised
}
----

==== Compliant solution

[source,csharp,diff-id=1,diff-type=compliant]
----
void Sample(bool condition)
{
    int? nullableValue = condition ? 42 : null;
    if (nullableValue.HasValue)
    {
      Console.WriteLine(nullableValue.Value);
    }

    int? nullableCast = condition ? 42 : null;
    if (nullableCast is not null)
    {
      Console.WriteLine((int)nullableCast);
    }
}
----

== Resources

=== Documentation

* https://learn.microsoft.com/en-us/dotnet/api/system.nullable-1[Nullable<T>]
* https://cwe.mitre.org/data/definitions/476[MITRE, CWE-476] - NULL Pointer Dereference

include::../rspecator-dotnet.adoc[]