== 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 `Nothing`.

The value stored 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 `Nothing`. 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,vbnet,diff-id=1,diff-type=noncompliant]
----
Sub Sample(condition As Boolean)
    Dim nullableValue As Integer? = If(condition, 42, Nothing)
    Console.WriteLine(nullableValue.Value)             ' Noncompliant: InvalidOperationException is raised

    Dim nullableCast As Integer? = If(condition, 42, Nothing)
    Console.WriteLine(CType(nullableCast, Integer))    ' Noncompliant: InvalidOperationException is raised
End Sub
----

==== Compliant solution

[source,vbnet,diff-id=1,diff-type=compliant]
----
Sub Sample(condition As Boolean)
    Dim nullableValue As Integer? = If(condition, 42, Nothing)
    If nullableValue.HasValue Then
        Console.WriteLine(nullableValue.Value)
    End If
            
    Dim nullableCast As Integer? = If(condition, 42, Nothing)
    If nullableCast.HasValue Then
        Console.WriteLine(CType(nullableCast, Integer))
    End If
End Sub
----

== 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[]
