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Control-of-FLOW language elements in ASP,

If-statements

IF condition THEN
  instruction that has to be done when true
ELSE
  instruction that has to be done when false
END IF

Example:

age=25
IF age<18 THEN
  response.write("Non-adult")
ELSE
  response.write("Adult")
END IF

With nesting you'll have to use ELSEIF 

IF condition1 THEN
  instruction that has to be done when first condition true
ELSEIF condition2 THEN
  instruction that has to be done when second condition true
ELSE
  instruction that has to be done when false
END IF

Select or Multiple choice-statement

SELECT CASE variable
  CASE value1
	instruction
  CASE value2
	instruction
  CASE ELSE
	else-instruction
END SELECT

variable Name of the variable that has to be tested
value1, value2,... A value for the test
instruction if the variable=value then the instruction is executed
else-instruction If the value of the variable is not one of the values listed the this instruction is executed

Example:

<% @language=vbscript %>
<HTML>
<HEAD><TITLE>Example on select-case</TITLE></HEAD>
<BODY>

<%
theday=Weekday(now())
response.write('The day of the week is "& theday &"<HR>")
SELECT CASE theday
  CASE vbSunday
	response.write("Sunday")
  CASE vbMonday
	response.write("Monday")
  CASE vbTuesday
	response.write("Tuesday")
  CASE vbWednesday
	response.write("Wednesday")
  CASE vbThursday
	response.write("Thursday")
  CASE vbFriday
	response.write("Friday")
  CASE vbSaturday
	response.write("Saturday")
  CASE ELSE
	response.write("Another day")
END SELECT
%>

</BODY>
</HTML>

FOR ... NEXT-statement

There are 2 versions of FOR, the classic one and FOR EACH.

FOR (clasic)

FOR variable= startvalue TO endvalue STEP stepvalue
  instruction
NEXT

Step value is not obligated, if you don't add it, the value is added 1 at each next instruction

Example:

<% @language=vbscript %>
<HTML>
<HEAD><TITLE>Example on For</TITLE></HEAD>
<BODY>

<%
FOR counter1= 1 TO 3
  response.write("<br>("& counter1 &")")
NEXT
%>

</BODY>
</HTML>

For each...next-statement

This instruction is executed for every element in a table or group. 

FOR EACH element IN group
  instruction
NEXT
element The name of the variable that contains the present value of the element from the group
group The name of the table or group
instruction The instruction that has to be executed

Example:

<% @language=vbscript %>
<HTML>
<HEAD><TITLE>Example on For</TITLE></HEAD>
<BODY>

<%
FOR EACH entry IN Request.form
  response.write( entry &" : "& request.form(entry))
  response.write("<br>")
NEXT
%>

</BODY>
</HTML>

This gets each entry and its value in a form (on a HTML-page)

Do while/until...loop-statement

Do while ... loop 

DO WHILE condition
  instruction
LOOP

When the condition is true the loop continuous. When the condition is false the loop is broken and the program continious.

A typical example is to get every element from a table(database). 

DO WHILE not rs.Eof
  response.write rs("name")
  response.write ("<br>")
  rs.movenext
LOOP

It is important you don't forget rs.movenext or you have a endless loop.

A DO WHILE ... LOOP will not be executed if the condition is immidiatly false.

A DO ... LOOP UNTIL will at least be executed once.

Example:

<% @language=vbscript %>
<HTML>
<HEAD><TITLE>Example do until</TITLE></HEAD>
<BODY>

counter1=0
DO 
  counter1=counter1+1
  response.write(counter1)
LOOP UNTIL counter1=10
%>

</BODY>
</HTML>

 

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