Nesting If/Else

[FZ1]

Seems like a simple thing...I have tried to nest If statements (I have seen examples on the web) but it doesn't seem to like it. If I put and "End IF" between every statement it likes it... Here it is as I have it nested. I can just do it the other day but it bothers me when I can't find out why it's no good.

		If Salesamount > 0 And Salesamount <= 5000 Then
			Salesamount = Salesamount * 0.01
			If Salesamount > 5000 And Salesamount <= 10000 Then
				Salesamount = Salesamount * 0.03
				If Salesamount > 10000 Then
					Salesamount = Salesamount * 0.07
				End If

[juanchoc]

You must end every IF with a End If, if what you want is nested Ifs...
A complete diferent story would be if what you want is a ElseIf, where you just need one End If at the end.

Try this:

        If Salesamount > 0 And Salesamount <= 5000 Then
            Salesamount = Salesamount * 0.01
        ElseIf Salesamount > 5000 And Salesamount <= 10000 Then
            Salesamount = Salesamount * 0.03
        ElseIf Salesamount > 10000 Then
            Salesamount = Salesamount * 0.07
        End If

Or this:

        If Salesamount > 0 And Salesamount <= 5000 Then
            Salesamount = Salesamount * 0.01
            If Salesamount > 5000 And Salesamount <= 10000 Then
                Salesamount = Salesamount * 0.03
                If Salesamount > 10000 Then
                    Salesamount = Salesamount * 0.07
                End If
            End If
        End If

Hope that helps.

[HanneSThEGreaT]

You also get a "Single Line" If Statement
Example:

If Sales > 1000 Then Profit = Profit * 2

Note that what should be done when Sales > 1000 is placed next to Then, and not underneath it - denoting a single line If statement.

[gigemboy]

I prefer using Select Case over a lot of If.. Else statements... I think its prettier

        Select Case SalesAmount
            Case Is < 5000
                MessageBox.Show("less than 5000")
            Case 5000 To 10000
                MessageBox.Show("between 5000 and 10000")
            Case Is > 10000
                MessageBox.Show("greater than 10000")
            Case Else
                MessageBox.Show("Invalid Value!!")
        End Select

[FZ1]

You must end every IF with a End If, if what you want is nested Ifs...

Thank you. I guess I had the wrong idea about nested IF statements. If you have to put an END IF statement after every line then I'm not seeing where nesting helps other than making the code a little easier (visually) to debug. Then again, maybe that's the point. The book I am using sucks. It's says you can nest them but doesn't give an example or define it.

[juanchoc]

It always depends on what you want to do.
Remember that there can be multiple levels of nesting, not just the linear example above.

[aniskhan]

u can have multiple levels of nesting like this

If condition Then
	If condition Then
		If condition Then

		End If
	End If
End If

[HanneSThEGreaT]

You could also have a nested Select Case Statement

Select Case Gender
    Case "Female"
      Select Case Age
         Case 20
        
         Case 30

     End Select
    Case "Male"
      Select Case Age
         Case 20
        
         Case 30

     End Select
End Select

[FZ1]

So guys, what is the benefit of nesting - just for visual clarity? It looks like it takes the same amount of coding. Sorry if this is a lame question but I'm all about efficiency and it doesn't appear to be more effiicient.

[Shuja Ali]

So guys, what is the benefit of nesting - just for visual clarity? It looks like it takes the same amount of coding. Sorry if this is a lame question but I'm all about efficiency and it doesn't appear to be more effiicient.

Basically you would avoid nesting Ifs and use a Select Case statement rather.

And it all depends on what you want to do?

[DeepButi]

So guys, what is the benefit of nesting - just for visual clarity? It looks like it takes the same amount of coding. Sorry if this is a lame question but I'm all about efficiency and it doesn't appear to be more effiicient.

What exactly do you understand by "nesting"?
Same amount of coding than what?
More efficient than what?

End If tells the compiler where the If ends.

Consider the following

If condition1 Then
    statement1
    If condition2 Then
        statement2
        If condition3 Then
            statement3
            statement4
        End If
        statement5
    End If 
    statement6
End If

How will you tell the compiler which statements are to be executed by every If without End If counterparts?

How will you code it without nested Ifs in a more efficient way?

[FZ1]

End If tells the compiler where the If ends.

How will you tell the compiler which statements are to be executed by every If without End If counterparts?

I understand that now but I guess I never got the answer to: what's the point of nesting?

Same amount of coding than what?
More efficient than what?

My original thought process was this - I thought (by assumption - I know this is bad) by nesting you would be able to only use 1 final "END IF" statement at the end of all the IF instructions thereby saving some coding and being more efficient. Also bear in mind that our homework assignment came from a problem in our text book which was nice enough to say: "(hint: You can nest an IF...THEN...ELSE statement, which means you can place one IF...THEN...ELSE statement inside another IF...THEN...ELSE statement.)" That's all the explanation I got and nowhere was it discussed in detail in the book. So, I took this to be telling me that its more efficient to do it this way so I guess I read a little into it but again, I wasn't given much to work with.

[FZ1]

OK, so I have been monkeying around with the code because that's the best way to learn, right? So when I code this:

		If Salesamount > 0 And Salesamount <= 5000 Then
			Bonus = Salesamount * 0.01
			If Salesamount > 5000 And Salesamount <= 10000 Then
				Bonus = Salesamount * 0.03
				If Salesamount > 10000 Then
					Bonus = Salesamount * 0.07
				End If
			End If
		End If

The program will only look at the first statement. If I enter an amount >5000 it will not return an answer. However, if I code it this way:

		If Salesamount > 0 And Salesamount <= 5000 Then
			Bonus = Salesamount * 0.01
		End If
		If Salesamount > 5000 And Salesamount <= 10000 Then
			Bonus = Salesamount * 0.03
		End If
		If Salesamount > 10000 Then
			Bonus = Salesamount * 0.07
		End If

The logic for all statements is evaluated and the correct results are displayed. This tells me there is a difference between the 2 ways of formatting the code other than being visually different. The question is, why is it interpreting it different and when would you want to use the nested version vs. the non? Again, the book is no help on the subject and apparently something we aren't going to learn in class

[aniskhan]

Using nesting depends on what u want to do , it depends on the logic u adapt to solve a problem.
very important in sophisticated programming like games, its good until it is in ur control, but turns bad if u loose control(diagrams used to draw the flow of control).
Although deeply nested structures are confusing, difficult to understand and maintain, so u should minimize the depth of nested control structures, not more then 5 levels.
following example will show the use of nesting. Counts the words in sentence.

   'ch is the sharacter from sentence
        If ch = " " Then ' It is a space 

            ' Handle spaces 
            If (inAWord) Then ' reset 
                inAWord = False
            Else ' Just another space
                  
            End If

        Else

            If inAWord Then ' It is part of a word 

            Else ' Starting a new word 
                numWords += 1  ' count it
                inAWord = True
            End If

        End If

[vanidosa27]

This is the way my text explains Nested If statements...

Nested, If/ElseIf/Else, and Case Selection Structures
Nested Selection Structures
You use the selection structure when you want a procedure to make a decision and then select one of two paths—either the true path or the false path—based on the result of that decision
Both paths in a selection structure can include instructions that declare and initialize variables, perform calculations, and so on
Both also can include other selection structures
When either a selection structure’s true path or its false path contains another selection structure, the inner selections structure is referred to as a nested selection structure, because I is contained (nested) within the outer selection structure
You use a nested selection structure when more than one decision must be made before the appropriate action can be taken
Assume you want to create a procedure that determines whether a person can vote, and then, based on the result of that determination, displays one of three messages
The person’s voter registration status is important only after his or her age is determined
You can think of the decision regarding the age as the primary decision, and the decision regarding the registration status as being the secondary decision, because whether the registration decision needs to be made by the outer selection structure, while the secondary decision is always made by the inner (nested) selection structure
The lines connecting the selection structures in the pseudocode and code are included in the figure to help you see which clauses are related to each other
The procedure begins by declaring the variables and then getting the age from the user
The condition in the outer selection structure then checks whether the age is greater than or equal to 18
If the condition is false, it means that the person is not old enough to vote
In that case, only one message—the “You are too young to vote.” message—is appropriate
After the message is displayed, both the outer selection structure and the procedure end
If the outer selection structure’s condition is true, it means that the person is old enough to vote
If he or she is registered, the instruction in the nested selection structure’s true path displays the “You can vote” message
Otherwise, the false path displays the “You need to register before you can vote” message
After the appropriate message is displayed, both selection structures and the procedure end
The nested selection structure in this procedure is processed only when the outer selection structure’s condition is true
The new example first declares the necessary variables and then gets the age from the user
However, rather than checking whether the age is greater than or equal to 18, the outer selection structure in this version checks whether the age is less than 18
If the condition is true, the instruction in the outer selection structure’s true path displays a message
If the condition is false, the instructions first get the registration status from the user, and then use a nested selection structure to determine whether the person is registered
Then it displays a message
Otherwise, it displays another message
The nested selection structure in this version is processed only when the outer selection is false
Both versions of the voter eligibility procedure produce the same results
Neither version is better than the other
Each simply represents a different way of solving he same problem