CIS 451: ASP.NET Debugging and Server-Side Includes Dr. Ralph D. Westfall February, 2009.

CIS 451: ASP.NET Debugging and Server-Side Includes

Dr. Ralph D. WestfallFebruary, 2009

Error Handling/Debugging client side vs. server scripts syntax errors logical errors good coding practices to minimize

errors testing your code debugging statements

Need to Identify as Server Script code will run on client if doesn't

have: <% [code] %> or <script language="VB" runat="server"> [code] </script> filetype needs to be .aspx, not .htm(l)

Syntax Errors spelling

Reesponse.Write("something") EndIf '2 words: needs a space

missing parts of control structures For but no Next If but no End If

extra parts for control structures extra Next or extra End If at end

Syntax Errors - 2 using a method as a property

Response.Write = "Welcome" don't use = with methods

using a property as a method buffer("true") properties are values, so need to use

=

Syntax Errors - 3 writing to a "read only" propertyDim prices() As Double = {3.00, 2.00}

prices.Length = 5 'read only property using Set to create an object

Set objMail = _ Server.CreateObject("CDO.Message")

'remove Set (ASP 3.0 still needs Set)

Logical Errors division by a variable that has value of

zero if Option Explicit or Strict is not On a = 2 c = a / b 'no value given for b

type mismatch e.g. can't do arithmetic with text 5 / "hello" missing period can cause a type mismatch a=CInt(RequestQueryString("card")) 5 / a

Good Coding Practices indent code inside loops and

conditionals "pretty listing" (automatic in VS.NET) For intI = 0 to 2 intJ = intI Next I

use comments where appropriate 'single quote creates a comment

Good Coding Practices - 2 use Option Strict at start of file

<%@ Page Language="vb" Strict="true"%>

forces you to use Dim for all variables helps spot spelling mistakes forces you to handle all type

conversions explicitlytxtCount.Text=CStr(intCount)

Good Coding Practices - 3 use consistent object naming prefixes

btnSubmit 'a button txtLastName 'a textbox for data

capitalize function names e.g. conversions CInt(7.3) 'Convert to Integer CCur(9.9) 'Convert to Currency

Good Coding Practices - 4 type checking: is data what you

expect? If IsNumeric(Request.Form("num")) Then intTot = intTot + intNum End If

type conversion: change data so it is usable

intValue = CInt(dblItem1 + dblItem2)

Good Coding Practices - 5 use subprocedures and/or functions

for anything substantial (5 or more lines?) that gets done in more than 1 place

advantages: shorter program easier to debug and maintain may be able to reuse them in other

programs

Good Coding Practices - 6 use "server-side includes" in .aspx

files <% 'prices.aspx file Dim dblProdPrice(11) dblProdPrice(0)=29.99 'etc. %> <html>  

advantages similar to subprocedures, etc. See Notes Page

Testing Your Code test the different ways a user could go

through the application example: shopping cart with 2 catalog pages

entry page to catalog page 1 to checkout entry page to catalog page 2 to checkout entry, catalog 1, catalog 2, checkout entry, catalog 2, catalog 1, checkout using browser Back button instead of form button? using link instead of button?

Testing Your Code - 2 test possible data values example: zip codes

boundary values (included, or not?) 00000 and 99999

values in between boundaries 00001 to 99998

out-of-bounds values negative #s? 6 digit #s? text #s? (ninety thousand and one)

VS Debugging Capabilities break points and icons for stepping

through code Step Into, Step Over, Step Out

special windows Locals, Output, Watch, View Stack,

etc.

Debugging Statements insert "trace" statements to

determine values before code where problem is

Response.Write([variable name]) use <form method="get" > so you

can see form input values in query string

MsgBox to show specific values

Debugging with "Include" Files some programmers put tracing

procedures in separate file add #include file=[trace file name] at top of file being debugged

need to then insert calls to trace file procedures in code

NET tracing capabilities

More on Server Side Includes special features for HTML files only?

extension is .shtml or .shtm so server knows that special processing required

#fsize - gives file size #flastmod - gives file last modified date

include works in both ASP and HTML # include - includes text (code) from

another file so it is processed as if it is in the current file

Server Side Include Issues data is text, so could use .txt as

extension can hide file by using .aspx extension Microsoft recommends .inc extension

to conveniently identify include files convenient way to keep data in

programs up-to-date e.g., put shopping cart product prices

data in an include, then update just that file

Using Server Side Includes in ASP.NET need to put "directive" in HTML

comments<!--#include file="file1.aspx"->'path not needed if in current directory can use physical path (address on

drive) <!--#include file="[C:\path\]file.aspx"-> can also use virtual path (server

address) <!--#include virtual="[path]/file.aspx"->

SSI Exercise view Using Server Side Includes click "basic page," View>Source,

edit URLs and Save As basic.shtml note: save it as .shtml, not .html

also save code for the other linked pages (includes) in same directory

modify include files view effects on basic.shtml in browser

CIS 451: ASP.NET Debugging and Server-Side Includes Dr. Ralph D. Westfall February, 2009.

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Transcript of CIS 451: ASP.NET Debugging and Server-Side Includes Dr. Ralph D. Westfall February, 2009.