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 the value is accessed to avoid the exception.

Noncompliant Code Example

public void Sample(bool condition)
{
    int? nullableValue = condition ? 42 : null;
    Console.WriteLine(nullableValue.Value); // Noncompliant

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

Compliant Solution

public 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);
    }
}

See

• MITRE, CWE-476 - NULL Pointer Dereference