If Else & ElseIF conditional program structure control in ASP

To control the structure and flow of script we use if then else conditional statements of VBScript used in ASP. By using different combinations of if else condition we can control the program execution flow as per requirement. Before going into more details on this let us try the basic syntax of if - condition - Then - Else - Endif syntax.

If  condition  Then
Script block 1  here if condition is true
Else 
Script block 2  here if condition is false 
EndIf

In the above script block we have first tested the condition and if it is TRUE then Script block 1 gets executed and if the condition is FALSE then script block 2 is executed.

Here is a simple sample code for printing greatest of two numbers.

Dim n1,n2
n1=25
n2=45
If n1 > n2 Then 
	Response.Write "Greatest number is" & n1
Else 
	Response.Write "Greatest number is" & n2
End If

By changing the assigned values to n1 and n2 we can check how the if else control structure works.

We can keep If conditions inside another If conditions but each If condition has to have matching End If condition. We call it nested If conditions. The above code is changed to add one more If condition inside main If condition.

Dim n1,n2
n1=-25
n2=-45
If n1 > n2 Then
	Response.Write " Greatest number is " & n1
  If n1 < 0 Then 
	Response.Write "First number is a negetive number" 
	End IF

Else 
	Response.Write "Greatest number is " & n2 
End If

Some places we can use ElseIF condition than using more nested If Else condition. Here is an example of uses of ElseIf Condition.

Dim my_num
my_num=40
If my_num < 100 Then 
		Response.Write "It is less than 100" & "<br>"
	If my_num < 50 Then
		Response.Write "It is less than 50 also" & "<br>"
	End If

ElseIf my_num > 200 Then
  Response.Write "It is greater than 200 " & "<br>"
Else
  Response.Write "This is greater than 100 but less than 200"&"<br>"
End if

Note that ElseIf doest not require an End If to close but the original If condition should have its own.

ElseIf condition can't be used just after one Else condition. Where as Else condition can be used before ElseIF condition.
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If Else and nested If conditional script control