Why is this an issue?
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
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
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
