VB.NET Switch Statement GoTo Case

Question

I am writing some code in VB.NET that uses a switch statement but in one of the cases it needs to jump to another block. In C# it would look like this:

switch (parameter)
{
    case "userID":
        // does something here.
    case "packageID":
        // does something here.
    case "mvrType":
        if (otherFactor)
        {
            // does something here.
        }
        else
        {
            goto default;
        }
    default:
        // does some processing...
        break;
}

However, I don't know how to convert this to VB.NET. I tried this:

Select Case parameter 
    Case "userID"
        ' does something here.
    Case "packageID"
        ' does something here.
    Case "mvrType" 
        If otherFactor Then 
            ' does something here. 
        Else 
            GoTo Case Else 
        End If 
    Case Else 
        ' does some processing... 
        Exit Select 
End Select

But when I do this I get a compiler error: "Identifier expected". There'sa squiggly line under "Case". Any ideas?

Also, is it wrong to use a GoTo statement in this case? It seems any other way I would have to re-write it.

I have changed my code to as follows:

If otherFactor AndAlso parameter = "mvrType" Then 
    'does something here 
Else 
    ' My original "Select Case statement" here without the case for "mvrType" 
End If

score 25 · Answer 1 · answered May 04 '09 at 13:42

25

Why not just do it like this:

Select Case parameter     
   Case "userID"                
      ' does something here.        
   Case "packageID"                
      ' does something here.        
   Case "mvrType"                 
      If otherFactor Then                         
         ' does something here.                 
      Else                         
         ' do processing originally part of GoTo here
         Exit Select  
      End If      
End Select

I'm not sure if not having a case else at the end is a big deal or not, but it seems like you don't really need the go to if you just put it in the else statement of your if.

answered May 04 '09 at 13:42

ryanulit

4,983
6
42
66

Also, the article below explains criticisms of the goto statement. http://en.wikipedia.org/wiki/GOTO#Criticism_of_goto_usage – ryanulit May 04 '09 at 13:48
This would means I would have to write the processing code twice; first for the "Else" case on the If statement, and second for the "Case Else" statement on the "Select" statement. I would have to update both, and its actually quite a few lines of code. It seems like a real bad idea. – KTF May 04 '09 at 14:00
It's a bad idea to have so much code duplicated, a bad idea to use goto, and a bad idea to have so much code (as implied by your comments) in a SWITCH structure. Extract the method (the duplicated code) into a function; also consider replacing polymorphism by inheritance. – Carl Manaster May 04 '09 at 14:11

Nick Berardi · Accepted Answer · 2009-05-04T13:58:02.617

There is no equivalent in VB.NET that I could find. For this piece of code you are probably going to want to open it in Reflector and change the output type to VB to get the exact copy of the code that you need. For instance when I put the following in to Reflector:

switch (args[0])
{
    case "UserID":
        Console.Write("UserID");
        break;
    case "PackageID":
        Console.Write("PackageID");
        break;
    case "MVRType":
        if (args[1] == "None")
            Console.Write("None");
        else
            goto default;
        break;
    default:
        Console.Write("Default");
        break;
}

it gave me the following VB.NET output.

Dim CS$4$0000 As String = args(0)
If (Not CS$4$0000 Is Nothing) Then
    If (CS$4$0000 = "UserID") Then
        Console.Write("UserID")
        Return
    End If
    If (CS$4$0000 = "PackageID") Then
        Console.Write("PackageID")
        Return
    End If
    If ((CS$4$0000 = "MVRType") AndAlso (args(1) = "None")) Then
        Console.Write("None")
        Return
    End If
End If
Console.Write("Default")

As you can see you can accomplish the same switch case statement with If statements. Usually I don't recommend this because it makes it harder to understand, but VB.NET doesn't seem to support the same functionality, and using Reflector might be the best way to get the code you need to get it working with out a lot of pain.

Update:

Just confirmed you cannot do the exact same thing in VB.NET, but it does support some other useful things. Looks like the IF statement conversion is your best bet, or maybe some refactoring. Here is the definition for Select...Case

http://msdn.microsoft.com/en-us/library/cy37t14y.aspx

Very interesting. What is the benefit of using Select statements? I thought a lookup table was used? Either way- this is what I suspected (that VB.NET did not support it) — KTF, May 04 '09 at 14:04
No a select statement or a switch statement is just compiler "magic" in .NET, it actually transforms everything in to a big harder to read if-else statement. — Nick Berardi, May 04 '09 at 16:36
Not always true (I know this comment is quite old, but it's new to me!) - http://blogs.msdn.com/abhinaba/archive/2006/12/13/why-can-we-only-use-constants-in-a-switch-case-statement.aspx — Ant, Nov 12 '09 at 08:55
@Ant: Nice! I always wondered about that... thanks for that additional comment! — KTF, Dec 18 '11 at 02:55

score 12 · Answer 3 · answered May 04 '09 at 14:02

12

Why don't you just refactor the default case as a method and call it from both places? This should be more readable and will allow you to change the code later in a more efficient manner.

answered May 04 '09 at 14:02

Nicolas De Irisarri

1,077
1
14
27

score 7 · Answer 4 · edited Jun 26 '12 at 21:34

In VB.NET, you can apply multiple conditions even if the other conditions don't apply to the Select parameter. See below:

Select Case parameter 
    Case "userID"
                ' does something here.
        Case "packageID"
                ' does something here.
        Case "mvrType" And otherFactor
                ' does something here. 
        Case Else 
                ' does some processing... 
End Select

Meta-Knight · Answer 5 · 2012-05-25T12:42:59.930

I'm not sure it's a good idea to use a GoTo but if you do want to use it, you can do something like this:

Select Case parameter 
    Case "userID"
        ' does something here.
    Case "packageID"
        ' does something here.
    Case "mvrType" 
        If otherFactor Then 
            ' does something here. 
        Else 
            GoTo caseElse
        End If 
    Case Else
caseElse:
        ' does some processing... 
End Select

As I said, although it works, GoTo is not good practice, so here are some alternative solutions:

Using elseif...

If parameter = "userID" Then
    ' does something here.
ElseIf parameter = "packageID" Then
    ' does something here.
ElseIf parameter = "mvrType" AndAlso otherFactor Then
    ' does something here.
Else
    'does some processing...
End If

Using a boolean value...

Dim doSomething As Boolean

Select Case parameter
Case "userID"
     ' does something here.
Case "packageID"
     ' does something here.
Case "mvrType"
     If otherFactor Then
          ' does something here. 
     Else
          doSomething = True
     End If
Case Else
     doSomething = True
End Select

If doSomething Then
     ' does some processing... 
End If

Instead of setting a boolean variable you could also call a method directly in both cases...

You are missing the point of the switch case specific GoTo, it doesn't act like a GoTo, just a procedural jump to another case. — Nick Berardi, May 04 '09 at 13:38
Yeah- What Nick Berardi is talking about is exactly what I need. Is there anything like that in VB.NET? — KTF, May 04 '09 at 13:40
I don't think there's such a thing as a switch case specific GoTo in Vb.Net. But I would probably use If/Elseif, or set some boolean variable to true and do the processing outside of the select case. — Meta-Knight, May 04 '09 at 13:51

score 3 · Answer 6 · answered May 04 '09 at 13:45

3

you should declare label first use this :

    Select Case parameter 
        Case "userID"
                    ' does something here.
            Case "packageID"
                    ' does something here.
            Case "mvrType" 
                    If otherFactor Then 
                            ' does something here. 
                    Else 
                            GoTo else
                    End If 

            Case Else 
else :
                    ' does some processing... 
                    Exit Select 
    End Select

answered May 04 '09 at 13:45

Sadegh

6,654
4
34
44

Same issue as Meta-Knight, you don't want to use actual GoTo statements. A GoTo in the a CASE statement is a procedural jump to another case, not a line jump as you have done above. – Nick Berardi May 04 '09 at 13:47
1

wasn't down voted because it didn't work, it was down voted because it is a bad solution and not the same thing as the original C# that the OP is trying to convert. – Nick Berardi May 04 '09 at 13:50

score 2 · Answer 7 · edited May 26 '15 at 15:07

2

Select Case parameter 
    ' does something here. 
    ' does something here. 
    Case "userID", "packageID", "mvrType" 
        If otherFactor Then 
            ' does something here. 
        Else 
            goto case default 
        End If 
    Case Else 
        ' does some processing... 
        Exit Select 
End Select

edited May 26 '15 at 15:07

DanM7

2,203
3
28
46

answered Sep 17 '09 at 03:19

score 0 · Answer 8 · answered Aug 13 '15 at 02:22

Select Case parameter 
    Case "userID"
        ' does something here.
    Case "packageID"
        ' does something here.
    Case "mvrType" 
        If otherFactor Then 
            ' does something here.
        End If 
    Case Else 
        ' does some processing... 
        Exit Select 
End Select

Is there a reason for the goto? If it doesn't meet the if criterion, it will simply not perform the function and go to the next case.

score 0 · Answer 9 · answered Jul 21 '21 at 18:35

There's a way that works now at least in Visual Basic 2017. It's not the prettiest though.

GoTo Case "[label]" and Goto [Case-label] still do not work.

The label (Number2 here) must be after the Case. That was the most disappointing part.

dim Value = "1"
Select Case Value
    Case "0"
       ' do nothing, example
    Case "1"
        MsgBox("one")
        GoTo Number2
    Case "2"
Number2:
        MsgBox("two")
    Case "boolean"
        MsgBox("three")
        ' just to show it won't fall through
End Select

score -1 · Answer 10 · edited Aug 29 '12 at 09:41

-1

Select Case parameter
    ' does something here.
    ' does something here.
    Case "userID", "packageID", "mvrType"
                ' does something here.
        If otherFactor Then
        Else
            goto case default
        End If
    Case Else
        ' does some processing...
        Exit Select
End Select

edited Aug 29 '12 at 09:41

j0k

22,600
28
79
90

answered Aug 29 '12 at 09:39

Taran

2,895
25
22

2

-1 `goto case default` (or `goto case else`) is a syntax error for me. – Mark Hurd Oct 05 '12 at 01:07

VB.NET Switch Statement GoTo Case

10 Answers10

Linked