Why is this an issue?

Visual Basic .NET offers a non-short-circuit conditional function, IIf(), which returns either its second or third parameter based on the expression in the first parameter. Using it is slower than using If() because each parameter is unconditionally evaluated. Further, its use can lead to runtime exceptions because IIf always evaluates all three of its arguments.

The newer version, If(), should be used instead because it short-circuits the evaluation of its parameters.

Noncompliant code example

Public Class Foo
    Public Sub Bar()
        Dim var As Object = IIf(Date.Now.Year = 1999, "Lets party!", "Lets party like it is 1999!") ' Noncompliant
    End Sub
End Class

Compliant solution

Public Class Foo
    Public Sub Bar()
        Dim var As String = If(Date.Now.Year = 1999, "Lets party!", "Lets party like it is 1999!")
    End Sub
End Class

Resources

• IIf Function (MSDN)
• If Operator (MSDN)