vb.net - IIF Throwing Strange Exception
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14-11-2019 - |
Domanda
Sto avendo un problema strano.IIF sta scherzando quando sto lavorando con un array.Apparentemente sta controllando la mia affermazione anche se non è attivata.Ecco alcuni codici che dimostrano il problema:
'works
Dim test As String = "bleh"
If values.Length < 6 Then
test = "200"
Else
test = values(5)
End If
'throws indexoutofrange exception
Dim itemLimit As String = IIf(values.Length < 6, "200", values(5))
. Soluzione
The Iif
operator doesn't implement short circuiting and will evaluate both the true and false case. If you want a short-circuit version then use If
.
Dim itemLimit As String = If(values.Length < 6, "200", values(5))
Altri suggerimenti
Have a look at this article: http://www.fmsinc.com/free/newtips/net/nettip33.asp
From the article:
Visual Basic, VBA, and Visual Basic .NET support the IIF function as an alternative to the If...Then...Else statement. Although this may seem like a shortcut, IIF functions differently than If...Then...Else.
IIF must evaluate the entire statement when preparing the argument, which can lead to undesirable side effects.
In other words, your If...Then...Else
works because the Else
clause isn't being evaluated if the condition fails. The IIf
, on the other hand, evaluates all the statements, causing the IndexOutOfBounds
exception.