[RESOLVED] Select Case Statement Question

[Ellis Dee]

The Select Case structure can only evaluate one variable. You have two: .Top and .Height. So you need to stick with If...ElseIf chains.

You can hack the Select Case as techgnome showed, but it's a nonstandard implementation -- a hack -- and therefore reduces the maintainability of your code.

[MartinLiss]

Why do you consider Select case True a nonstandard hack? Concerning the construct MS says:

A Select Case structure works with a single test expression that is evaluated once, at the top of the structure. Visual Basic then compares the result of this expression with the values for each Case in the structure. If there is a match, it executes the block of statements associated with that Case:

"True" is a test expression (albeit a very simple one) just like any other test expression.

[Ellis Dee]

"True" is a test expression (albeit a very simple one) just like any other test expression.

Not in this case. Top and Height are the test expressions, not True.

The whole point of the Select Case construct is to evaluate a single expression. The Select Case True hack is conceptually the exact opposite of that, where the series of cases are completely unrelated to one another. That's what makes it a nonstandard hack.

[MartinLiss]

Not in this case. Top and Height are the test expressions, not True.

The whole point of the Select Case construct is to evaluate a single expression. The Select Case True hack is conceptually the exact opposite of that, where the series of cases are completely unrelated to one another. That's what makes it a nonstandard hack.

I won't clutter this thread up any more after this but see the following and many others...
http://www.devx.com/tips/Tip/15288
http://c2.com/cgi/wiki?VbFlexibleSelectCase
http://social.microsoft.com/Forums/e...3-128cd8d551d5

[Ellis Dee]

Ihttp://www.devx.com/tips/Tip/15288

This example argues that this is more elegant than If...ElseIf chains:

Select Case True
    Case TypeOf c Is TextBox
    Case TypeOf c Is ComboBox
    Case TypeOf c Is ListBox
    Case TypeOf c Is CheckBox
    Case TypeOf c Is OptionButton
End Select

The better way, which is more elegant still:

Select Case TypeName(c)
    Case "TextBox"
    Case "ComboBox"
    Case "ListBox"
    Case "CheckBox"
    Case "OptionButton"
End Select

http://c2.com/cgi/wiki?VbFlexibleSelectCase

The "BeginsWith" hack is a very nice hack, but it's still a hack. And I still probably wouldn't use that technique. Instead, I'd probably tokenize the line, identify the type of declaration (function, sub, property) using a dedicated function that returns an enumerated declaration type. That enumerated value would then get processed by a Select Case structure.

phttp://social.microsoft.com/Forums/e...3-128cd8d551d5

This just looks like you googled "Select Case True" and linked the first three results you found.

I don't dispute that it functions. I'm disputing that it's a best practice. The fact that none of your links are affiliated with Microsoft in any way is pretty good evidence that this technique is, in fact, a nonstandard hack.

[Pradeep1210]

This example argues that this is more elegant than If...ElseIf chains:

Select Case True
    Case TypeOf c Is TextBox
    Case TypeOf c Is ComboBox
    Case TypeOf c Is ListBox
    Case TypeOf c Is CheckBox
    Case TypeOf c Is OptionButton
End Select

I wonder how that Select...Case structure is superior to the If..ElseIf..End If structure.
Does anyone see any clear gain here? It doesn't save you with any significant typing work, nor does it add any performance gain etc.

If TypeOf c Is TextBox Then
ElseIf TypeOf c Is ComboBox Then
ElseIf TypeOf c Is ListBox Then
ElseIf TypeOf c Is CheckBox Then
ElseIf TypeOf c Is OptionButton Then
End If

[MartinLiss]

I wonder how that Select...Case structure is superior to the If..ElseIf..End If structure.
Does anyone see any clear gain here? It doesn't save you with any significant typing work, nor does it add any performance gain etc.

According to a test I just did with GetTickCount the Select Case code is about 10% faster.