Difference between If statements and Cases

[halo combat22]

What is the difference between them and when to use them where?

[richerTextBox]

Technically, there is no difference. It's simply a matter of formatting your code.
To explain, if you had multiple boolean conditions to test, your code starts to get jumbled-looking with multiple IF statements. Compare the two methods below:

If text = "Black" Then
    'Code executes here...
Else If text = "Yellow" Then
    'Code executes here...
Else If text = "Green" Then
    'Code executes here...
Else If text = "Red" Then
    'Code executes here...
End If
 
**********   Now compare the CASE statement  *******
 
Select Case text
    Case "Black"
         'Code executes here...
    Case "Yellow"
         'Code executes here...
    Case "Green"
         'Code executes here...
    Case "Red"
         'Code executes here...
End Case

So in the end it's up to the programmer but it makes your code far more readable to use CASE on multiple condition testing.

Cheers!
Richard

[BlackMustard]

Technically, there is no difference. It's simply a matter of formatting your code.
To explain, if you had multiple boolean conditions to test, you code starts to get jumbled looking with multiple IF statements. Compare the two methods below:

If text = "Black" Then
    'Code executes here...
Else If text = "Yellow" Then
    'Code executes here...
Else If text = "Green" Then
    'Code executes here...
Else If text = "Red" Then
    'Code executes here...
End If
 
**********   Now compare the CASE statement  *******
 
Select Case text
    Case "Black"
         'Code executes here...
    Case "Yellow"
         'Code executes here...
    Case "Green"
         'Code executes here...
    Case "Red"
         'Code executes here...
End Case

So in the end it's up to the programmer but it makes your code far more readable to use CASE on multiple condition testing.

Cheers!
Richard

note that the spaces between "Else" and "If" in richard's code ("Else If" for each new condition) really shouldn't be there. if you put a space between, you need a separate End If at the end of each If clause, and they would all pile up at the end, making the code look even worse... but the idea was right ;)

and his main point stands uncorrected: the code is far more readable (and therefore easier to amend or troubleshoot), and also as far as i know slightly more effective to run. i might be corrected on that point though...

[Killer42]

and his main point stands uncorrected: the code is far more readable (and therefore easier to amend or troubleshoot), and also as far as i know slightly more effective to run. i might be corrected on that point though...

Couldn't say for sure, but my guess would be that a bunch of ElseIf's would produce the same compiled code as Case statements.

Note however, the main difference is that Select Case works based on the value of an expression which is evaluated at the start, while the If/ElseIf tests can be totally unrelated to each other if necessary. In other words, where the example says...

Select Case text
  Case "Black"
    ' Code executes here...
  Case "Yellow"
    ' Code executes here...
  Case "Green"
    ' Code executes here...
  Case "Red"
    ' Code executes here...
End Case

You could be wanting to check different situations. For instance...

If Text = "BLACK" Then
  ' Do something.
ElseIf AgeNextBirthday < 38 Then
  ' Do something else.
ElseIf MyName = "Earl" Then
  ' Do something else again.
Else
  ' Don't do anything.
End If

[AHMEDYO]

hi all

i think the most clear different is select case only work with constanct values

u cant say

select case (x)
case y: ' wrong
end select

but u can say

if (x=y) Then
''''
end if

[Killer42]

i think the most clear different is select case only work with constanct values ...

Actually, I think you're mistaken about that. I'll check and get back to you. (It'll have to wait until lunch time, though.)

[AHMEDYO]

Actually, I think you're mistaken about that. I'll check and get back to you. (It'll have to wait until lunch time, though.)

ok man ,,waiting your reply

[AHMEDYO]

ok man ,,waiting your reply

HI...

you are right Killer42, i was confused about Visual Basic and Visual C++ , because i am ordinary use Case statement only with C++

visual basic will accept this select statement

    Dim i As Long, y As Long, z As Long
    Select Case i
 
    Case y:
        MsgBox "ok"
    Case z:
 
    End Select

with visual C++ you will have error

    DWORD X,Y,Z;
    switch (Z)
    {
    case X:
 
        break;
    case Y:
 
        break;
    }

main.cpp(16) : error C2051: case expression not constant
main.cpp(19) : error C2051: case expression not constant

Sorry Guys.

[Mohan Krishna]

Hi everyone!

If I am not wrong...

Killer2 is right.
The "Switch...case" is used on one variable and whose value is in a list of constants (an Array like). But in the case of "if...else", it is quite observable that the expressions (or conditions) on different variables can be used.

Is'nt it?

ThnQ

[Killer42]

Sorry, haven't had a chance to check yet. I've been very busy.