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 “ Click here ” 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 = “ ” then Response.Write “Please enter your address.” ElseIf varConfirm = “Voic ” 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 “ Fax Case “Telephone” Response.Write “ Telephone Case “ ” Response.Write “ 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. ” 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. ” 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. ” 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 ForNext One Response Weekly Client Contacts for George Washington <% varStart=CDate(Request.Form("start")) varEnd=CDate(Request.Form("end")) varNumberDays=(varEnd-varStart) For varLineCounter = 0 to varNumberDays Response.Write "Clients: ___________________" Response.Write " " Next %> signed _________________________ George Washington

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 & “ ” Next %>

ASP-5-20 Do While Example Do While Sales Calls for This Month <% varRowCount = 1 varTodayDate = day(now()) Do While varRowCount <= varTodayDate Response.Write "For ____________ " Response.Write "number of clients met was ______ " varRowCount = varRowCount + 1 Loop %>

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 for a test condition when = 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 ” 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)