Upload
maryann-holt
View
222
Download
0
Embed Size (px)
Citation preview
ASP-5-1
ASP Control Structures
Colorado Technical University
IT420
Tim Peterson
ASP-5-2
Definitions
• Flow - Order of execution of statements.
• Execution - Process of carrying out the instruction in a statement.
• Action Statement - Statements that perform an activity.
• Control Statement - Statements that provide instructions on which statements to execute.
• Code Structures - Several lines of a code that achieve a task.
• Control Structures - a set of statements that govern the order of execution.
ASP-5-3
Control Statements
• Three types of control statements exist:– Branching Structures - Perform a test
• If..Then..Else
• Select Case
– Looping Controls - allow same block of code to run repetitively.
• For Next
• Do While
– Jumping Controls - allows the programmer to pass execution to another block of code.
• Subprocedure
• Function
ASP-5-4
If Then Else
• If Then Else can consists of four parts:– An expression used to test for a true false
answer– “if true” section of code– “if false” section of code– Ending statement
ASP-5-5
If Then Else Examples
• If Then Else can be built four different ways:– 1st method - Used if you only have one
statement to perform in case of a “true” test<%
If varFaxConfirm = “Yes” then Response.Write “Please enter your fax number”
%>
ASP-5-6
If Then Else Examples - Cont’d
– 2nd method - Used if you have more than one statement to execute in the case of a “true” test
<%
If varFaxConfirm =“Yes” Then
Response.Write “Please click below and provide your fax number.”
Response.Write “<A HREF=http://www.ctu.com/FaxForm>Click here</A>”
End If
%>
ASP-5-7
If Then Else Examples - Cont’d
– 3rd method - Used if you want to perform one state in the case of a “true” and a “false” test.
<%
If varFaxConfirm =“Yes” Then
Response.Write “Please enter your fax number.”
Else
Response.Write “No fax confirmation will be sent.”
End If
%>
ASP-5-8
If Then Else Examples - Cont’d
– 4th method - Used to continually nest statements using ElseIf
<%
If varConfirm = “Fax” then
Response.Write “Please enter your fax number.”
ElseIf varConfirm = “Email” then
Response.Write “Please enter your email address.”
ElseIf varConfirm = “Voicemail” then
Response.Write “Please enter your voice mail number.”
Else
Response.Write “No confirmation will be sent.”
End If
%>
ASP-5-9
If Then Else Common Errors
• Devising a test that does not resolve to true or false
• Leaving out the End If
• Leaving out the Else
• Coding End If as EndIf
• Multiple tests can only be accomplished with the ElseIf.
ASP-5-10
Select Case
• Select Case consists of four parts:– State which variable to test– State a possible answer and what to do if the
answer is a match– Repeat for all possible answers that are to be
handled– End the Select Case Structure
ASP-5-11
Select Case Examples
– 1st example - This is the simplest method:<%
Select Case varConfirmation
Case “Fax”
Response.Write “<A HREF = ‘FaxConfirmation.asp’ >Fax</A>
Case “Telephone”
Response.Write “<A HREF = ‘Telephone.asp’>Telephone</A>
Case “Email”
Response.Write “<A HREF = “Email.asp’>Email</A>
End Select
%>
ASP-5-12
Select Case Examples - Cont’d
– 2nd example - Illustrates how to process data that does not match any selection criteria.
<%
Select Case varMonthPref
Case “march”
Response.Write “Your meeting will be held on March 15th “
Case “March”
Response.Write “Your meeting will be held on March 15th “
Case “april”
Response.Write “Your meeting will be held on April 16th “
Case “April”
Response.Write “Your meeting will be held on April 16th “
Case Else
Response.Write “your request for “ & varMonthPref
Response.Write “is not recognized. Please click the back button on your browser “
Response.Write “and reset then re-enter the form data again. <BR>”
End Select
%>
ASP-5-13
Select Case Examples - Cont’d
• 3rd Example - Multiple selection criteria can be used for one Case statement.
<%
Select Case varMonthPref
Case “march”, “March”, “mar”, “Mar”, “MAR”
Response.Write “Your meeting will be held on March 15th “
Case “april”, “April”, “apr”, “Apr”, “APR”
Response.Write “Your meeting will be held on April 16th “
Case Else
Response.Write “your request for “ & varMonthPref
Response.Write “is not recognized. Please click the back button on your browser “
Response.Write “an reset then re-enter the form data again. <BR>”
End Select
%>
ASP-5-14
Select Case Examples - Cont’d
• 4th Example - Lets fix the case problem.<%
Select Case Lcase(varMonthPref)
Case “march”, “mar”
Response.Write “Your meeting will be held on March 15th “
Case “april”, “apr”
Response.Write “Your meeting will be held on April 16th “
Case Else
Response.Write “your request for “ & varMonthPref
Response.Write “is not recognized. Please click the back button on your browser “
Response.Write “an reset then re-enter the form data again. <BR>”
End Select
%>
ASP-5-15
Common Select Case Errors
• Putting more than one variable on the Select..Case line.
• Not making answers mutually exclusive.• Not have a possible answer for each case line.• Typing Select Case or End Select as one word.• Finishing the structure with End Case instead of
End Select
ASP-5-16
For Next
• For Next statement consists of three parts:– First line describes how many times to go
through the loop.– 2nd- A set of lines that define the action
statements to carry out within the loop.– 3rd - Final line indicates the end of the action
statements and tells ASP to go back and start the loop over.
ASP-5-17
For Next Example
<HTML>
<HEAD>
<TITLE>ForNext One Response</TITLE>
</HEAD>
<BODY>
<H2>Weekly Client Contacts for George Washington</H2><BR>
<%
varStart=CDate(Request.Form("start"))
varEnd=CDate(Request.Form("end"))
varNumberDays=(varEnd-varStart)
For varLineCounter = 0 to varNumberDays
Response.Write "Clients: ___________________"
Response.Write "<BR ><BR><BR>"
Next
%>
signed _________________________
George Washington
</BODY>
</HTML>
ASP-5-18
Common For..Next Errors
• Leaving out the counter variable
• Forgetting “=“ or the “to” on the first line
• Leaving out the Next statement
• Forgetting the start or end number
ASP-5-19
For Each..Next
• This is used for array elements and ASP objects.<%
Dim Item
Dim strCities(1)
strCities(0) = “Colorado Springs”
strCities(1) = “Denver”
For Each Item in strCities
Response.Write Item & “<BR>”
Next
%>
ASP-5-20
Do While Example
<HTML>
<HEAD>
<TITLE>Do While</TITLE>
</HEAD>
<BODY>
<H1>Sales Calls for This Month</H1><BR>
<%
varRowCount = 1
varTodayDate = day(now())
Do While varRowCount <= varTodayDate
Response.Write "For ____________ "
Response.Write "number of clients met was ______<BR>"
varRowCount = varRowCount + 1
Loop
%>
</BODY>
</HTML>
ASP-5-21
Common Do..While Errors
• Using Next instead of Loop for closing statement
• Not changing the expression variable (infinite loops)
• Performing one too many or few cycles.
• Using < or >for a test condition when <= or >= should have been used.
ASP-5-22
DO Loop..While
• This is a variation and forces the code to be executed once before an evaluation is accomplished:
Do
.. Place code here.
Loop While varRowCount <= varTodayDate
ASP-5-23
Jumping Structures
• Allow you to reuse code.• Subprocedures are used to carry out an action .e.g
putting text on a page.• Functions carry out action statements and return a
result.• Procedures require the following:
– Name
– Code in the body of the procedure
– Ending statement
ASP-5-24
Subprocedure Examples
Sub SalesContactInfo
Response.Write “Price quotes can be obtained from”
Response.Write “Tom at 719-555-1234.<BR>”
End Sub
many lines about gears
Call SalesContactInfo
…
many lines about bolts
Call SalesContactInfo
…
ASP-5-25
Functions
• Written similar to procedures• 1st line of a function starts with “Function”• Last line of a function is “End Function”• Function usually receive a parameter
– Function SimpleDollar(varMoney)
• The function name becomes the variable passed back out of the function “SimpleDollar”
• Functions are called by just typing its name– varMyMoney = SimpleDollar(BigMoney)