CIS 451: ASP.NET Objects Dr. Ralph D. Westfall January, 2009

Object Oriented Programming many popular newer programming languages are object-oriented C++, Java, JavaScript Visual Basic.NET is a true object- oriented (OO) language in contrast to VB 6 (which however did have objects with very useful properties)

What Is an Object? 3 types of things grouped together properties (like variables: descriptive) like a "super" variable (cf. hours PM) methods (like functions: actions) events (things that it responds to) similarities with real world objects car (properties? methods? events?) dog " "

Object Features properties: name/value pairs age = 21; height = 66"; weight = 135#; methods: code that does something calculations, write to screen, send may have either/both of following: parameters (inputs) return values (outputs)

Object Features - 2 events: things happen, object responds to them like a method, but triggered externally user clicks a button, or time runs out can have parameters and/or return values asynchronous: can occur at any time rather than scheduled, or at same time as something else (synchronous)

Other Object Concepts class = template or general model instance of class has specific attributes telephone = class, my phone = instance encapsulation: details of object hidden inside a "black box" only need to know the interface: how to call the methods and what the inputs and/or outputs are

Other Object Concepts - 2 "dot" notation identifies attributes and methods of objects Request.TotalBytes Request.QueryString.Count Count (of arguments) in QueryString is a property of Request Object Response.Write() Write is a method of Response Object

ASP Core Objects Request: messages from caller (e.g., web page or process) Response: messages to caller (browser) Server: variables and utility functions Application: data storage in memory for all web pages in the application Session: identifies individual user interactions

Request Object html or another asp file requests an asp file Request Object has information from page that requested the asp file information is stored in "collections" contain pairs of variable names and their values (name/value pairs) data values can be accessed by item name Request.QueryString("page")

Request Object Data "get" method in HTML calling page "get" appends data to URL (URL encoding) limit around 1000 characters (256 – 2000+) data available in Request.QueryString "collection," indexed by name of form element Request.QueryString("page") form has textbox, textarea, checkbox, radio button, or etc. element with name="page"

URL Encoding ? after URL shows start of data pairs of: name=value & (ampersands) between pairs + between separate words (= space) special characters coded as %nn (+ is %2B) …?cust=Jabbar&address=231+10th+St example: try doing a Yahoo searchYahoo

Request Object Data - 2 "post" method in HTML calling page sends data by a separate route size is essentially unlimited data available through Request.Form "collection," indexed by name of form element Request.Form("prod1") form has textbox, textarea, checkbox, radio button, or etc. element with name="prod1"

Get versus Post get (Request.QueryString) [object.property]) better for debugging (can look at query string in URL box on browser) post (uses Request.Form) can handle more data safer (less susceptible to hacking) always use post for database updates easy to convert Request.QueryString to Request.Form with global search/replace

Using QueryString in an aspx File can create the same effect sending from an aspx file as from a html file Response.Redirect("rsp.aspx?Name=" & _ this.txtName.Text & "&LastName=" & _ this.txtLastName.Text) values are URL encoded and visible in browser address of destination page one way to migrate from html to aspx

Response Object sends information to client can control when and how to send it can control caching/expiration of page can send parts or all of a web page to client

Response Methods Response.Write(x1 [& " " & x2 [&...]]) x1 etc. can be anything printable (text, #s, etc., or functions that return printable characters).NET has parentheses hold argument(s) same effect as Response.Write, in less space less efficient (don't use <%= a lot)

Response Methods - 2 redirecting to another page Response.Redirect("buya.aspx") stops processing on current page and goes to the other page can go to external pages too

Server Transfer Method can also use to redirect to another page, but only if it's on same server Server.Transfer("buya.aspx") doesn't change URL in browser address comparison of Response.Redirect and Server.Transfer comparison

Exercise: Form Processing use Dreamweaver to create a form that uses 8+ form elements/variations in its Windows>Objects>Forms toolbar set name property for each element select options (e.g., text input can be single or multiline, or password) see HTML Form Reference for syntaxHTML Form Reference save file as a.html file

Exercise: Form Processing - 2 use Visual Studio to create a project add the.html file you created on the previous page to the project create a.aspx file with Response.Write statements to print inputs/selections from each input element from the.html file test it on your workstation or computer

Multiple Selection Data can allow multiple selections in a list box on a form Paris Sydney Buenos Aires may send multiple items with same name ("loc" in this example)

Multiple Selection Data - 2 For intI = 1 to _ Request.Form("loc").Count Response.Write _ (Request.Form("loc")(intI)) Next note dot connecting Form object's ("loc") item to Count