Possible Duplicate:
Is there a conditional ternary operator in VB.NET?
Can we use the Coalesce operator(??) and conditional ternary operator(:) in VB.NET as in C#?
4 Answers
I think you can get close with using an inline if statement:
//C#
int x = a ? b : c;
'VB.Net
Dim x as Integer = If(a, b, c)
5 Comments
Nick Josevski
*Note: using the if statement that way only applies in VB.NET 2008 and onwards.
Guillermo Prandi
To use the If() function as a coalesce operator, it must be called with just two parameters, and it must be used for reference types:
Dim objC = If(objA,objB) This would set objC to objA unless objA is Nothing, in which case objC would be set to objB, whether it is Nothing or not.
brandito
For 2006+ support use IIf from memory?
jmoreno
@Brandito: the
IIF function is just that, a function, one that you could write yourself. It does not do coalescence, you would have to write that function yourself. If is a builtin operator, and does do coalescence if you only provide 2 arguments.
Brain2000
Given that IIf( ) is a function and If( ) is not, the main side effect is that If( ) only evaluates the true/false side, where IIf( ) will evaluate BOTH sides, even if it only returns one of them.
Sub Main()
Dim x, z As Object
Dim y As Nullable(Of Integer)
z = "1243"
Dim c As Object = Coalesce(x, y, z)
End Sub
Private Function Coalesce(ByVal ParamArray x As Object())
Return x.First(Function(y) Not IsNothing(y))
End Function
2 Comments
miroxlav
Utilizing LINQ, this is the most effective
Coalesce() implementation around.
James Curran
The problem with this (and ivan's below), is that all parameters will be evaluated. So, if I write
Dim thingie = Coalesce(Session("thingie"), new Thingie) a new Thingie object will be created every time (although it will be thrown away if a Thingie exist in the Session)just for reference, Coalesce operator for String
Private Function Coalesce(ByVal ParamArray Parameters As String()) As String
For Each Parameter As String In Parameters
If Not Parameter Is Nothing Then
Return Parameter
End If
Next
Return Nothing
End Function
Comments
If should be IIf
Dim x as Integer=IIf(a,b,c)
1 Comment
LosManos
Nope. IIf evaluates all parameters since it is a regular call. See dotnetslackers.com/VB_NET/…
Dim x = Obj?.Child?.AnotherChild?.Something?.AStringx is a string that will be Nothing if any object is nothing, or set if all objects are not nothing.