Question 235614 in Visual Studio Code Question posted in
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Visual Studio Code – In VB: convert a string to a statement label

In Visual Basic, is there a way to convert a string, entered on the command line, to a statement label? The intent is to execute only select portions of code. I’m working with a large program that includes many individual steps. For testing purposes I want to execute just one step without having to run through all of the previous steps.
I know how to extract the desired substring from the command line argument list.

So, given that string TestStep = "Step_3:"

somehow convert TestStep to point to label "Step_3:

GoTo TestStep
...
Step_1: 'do something
   GoTo Elsewhere
Step_2: 'do something else
   GoTo Elsewhere
Step_3: ' do the thing we want
   GoTo Elsewhere
Step_4: ' do other stuff
   GoTo Elsewhere
...

I’ve looked in "Visual Basic.NET" by Jesse Liberty and "VB.NET Language Pocket Reference" by Roman, Petrusha & Lomax without success.
Of course, just trying
GoTo TestStep where TestStep is a string results in Visual Studio responding: Label "TestStep" not defined

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2

Answers


  1. 0

    I had a similar problem with a large and complicated Select..Case block that I didn’t like due to potential complexity. I solved it by using Action variable type and a Dictionary of function pointers as below.

    <TestMethod>
Public Sub TestMethod1()

    Dim stepsToExecute As Dictionary(Of String, Action) = CreateStepsArray()

    Dim testStep As Action = stepsToExecute("Sub1")
    testStep()
    testStep()
    testStep = stepsToExecute("Sub2")
    testStep()

    testStep = stepsToExecute("Sub3")
    testStep()

End Sub

Private Function CreateStepsArray() As Dictionary(Of String, Action)
    Dim functionsList As New Dictionary(Of String, Action) From
    {
        {"Sub1", AddressOf Sub1},
        {"Sub2", AddressOf Sub2},
        {"Sub3", AddressOf Sub3}
    }

    Return functionsList
End Function

Private Sub Sub1()
    Debug.WriteLine("Sub 1")
End Sub

Private Sub Sub2()
    Debug.WriteLine("Sub 2")
End Sub

Private Sub Sub3()
    Debug.WriteLine("Sub 3")
End Sub

    When the test is run, it will produce this output:

    Sub 1
Sub 1
Sub 2
Sub 3
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  2. 0

    The lightest touch that I can think of would be something based on Select Case which would probably also require labels and GoTos to jump between cases. My idea is that if you started with something like this (not actually executable VB code, more like a VB-Fortran hybrid pseudocode):

    Dim target As String
Dim label As Object

Assign target To Label 'Hypothetical nonexistent Fortran-style "assigned GoTo"

GoTo Label

Qwerty:
' Stuff to do under one label

Dvorak:
' Stuff to do under another

Uiop:
' Stuff to do under a third

    Then maybe it could convert to something like this:

    Dim target As String

Select Case target
    Case "Qwerty"
        'Stuff
        'If (and only if) it should fall through
        GoTo Dvorak

    Case "Dvorak"
Dvorak:
        'Stuff
        'Optional fall-through
        GoTo Uiop

    Case "Uiop"
Uiop:
        'Stuff
End Select
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