Introduction to ASP.Net ISYS 512
Web Server Web Server: IIS Default directory Default home page Internet Information Service: ControlPanel/AdministrativeTools/Internet Information Services Built-in Web Server VS 05 uses the built-in web server for debugging. IIS Default directory C:\InetPub\wwwroot Default home page Default.aspx, default.asp, default.htm ASP.Net project directory Note: Using the Built-In web server, a web project can be created in any folders.
Web Project (Optional:) Start Internet Information server File/New Website/ ASP.Net Application Website folder Web form: default.aspx Design view and source (HTML) view Default.Aspx.VB CodeBehind Inline coding To set start up page: Point to the web page in the Solution Explorer and right click to choose Set As Start Page.
Inline Coding Example <body> <p>The time is now <%=Now.TimeOfDay()%></p> <p>The time is now <% response.write(Now.TimeOfDay())%></p> <% dim iHour iHour=Now.Hour() if iHour < 12 then response.write("<h1>good morning</h1><br>") else response.write ("<h1>good afternoon</h1><br>") end if %> </body>
VS WebForm Design View Layout/Position/Auto-Position Options HTML Designer CSS Positioning Absolutely positioned Relative
VS Web Project Demo Adding two numbers Creating bound DataGrid by dragging a table from the Server Explorer
HTML Introduction Heading section Body section <head>, <title>, <meta>, <script>, etc. Body section <body>, <p>, <h1> to <h6>, <a>, <br> Formatting: <b>, <I>, <u>, <center> Comment: <!-- comment --> List <ul> Image Table: <table>, <tr>: a new row in table, <td>: a new cell in a table row. Form: <form>, <input>, <select>, <textarea>
META Tag The meta tag allows you to provide additional information about the page that is not visible in the browser: <meta name=“Author” content=“D Chao”> <meta name=“Keywords” content=“apple, orange,peach”> Redirection: <meta http-equiv=“refresh” content=“3;url=http://www.sfsu.edu”> “3” is number of seconds. Demo using FrontPage
TABLE Tag <table border="1" width="100%"> <tr> <td width="25%"></td> <td width="25%"> </td> </tr> </table>
FORM Tag Form attribute: Demo: TestFormGet.Htm, TestFormPost.Htm Action: Specify the URL of a program on a server or an email address to which a form’s data will be submitted. Method: Get: the form’s data is appended to the URL specified by the Action attribute as a QueryString. Post: A prefered method for database processing. Form’s data is sent separately from the URL. Name: Form’s name Demo: TestFormGet.Htm, TestFormPost.Htm
QueryString A QueryString is a set of name=value pairs appended to a target URL. It can be used to pass information from one webpage to another. To create a QueryString: Add a question mark (?) immediately after a URL. Followed by name=value pairs separated by ampersands (&). Example: <A Href=“http://my.com/Target.htm?CustID=C1&Cname=Chao”>
Creating a QueryString Entered with a URL: http://dchaolaptop/testFormGet.aspx?cid=c2&cname=bbb As part of a URL specified in an anchor tag. <A Href=“http://my.com/Target.htm?CustID=C1&Cname=Chao”> Via a form sent to the server with the GET method. Created by script
SCRIPT Tag Client-side script: Server-side script: <SCRIPT LANGUAGE = VBSCRIPT> <!-- statements --> </SCRIPT> Server-side script: <script language=“VB” runat=“server”> </script>
ASP.NET ASP.NET is a server-side technology for creating dynamic web pages. ASP.NET allows you to use a selection of full programming languages. The default language is VB .NET. ASP.NET files have a .aspx extension.
ASP.NET in the .NET Framework 1. The client requests a web page. 2. The web server locates the page. 3. If the page is an ASP.NET page, it is sent to the Common Language Runtime for compilation and execution. 4. The HTML produced by the CLR is returned to the browser.
Benefits of Server-Side Technology Browser compatibility: Every browser reads HTML. Protection of source code. Controls are server-side objects with properties, methods and events. Separating code from content. CodeBehind
Elements of an ASP.Net Page Directives Code blocks ASP.NET controls HTML tags and text
Directives A directive controls how an ASP.Net page is compiled. Page directives: Specify default language, enable tracing and debugging for a page. <%@ Page Language=“VB” %>, <%@ Page Language=“C#” %> <%@ Page Trace=“True” %> Imports name spaces To process Access database, we need to import: <%@ Import Namespace=“System.Data” %> <%@ Import Namespace=“System.Data.Oledb” %>
Inserting ASP.NET Code into Web Pages Place ASP.NET code between <script> and </script> with a RUNAT attribute. <script language=“VB” runat=“server”> Your script </script> <script runat="server"> ---- ASPNET/ADD2.ASPX sub clickHandler(Sender As Object, E As EventArgs) sum.text=cstr(cdbl(num1.text)+cdbl(num2.text)) end sub Inline Code Block: ASP code is placed between <% and %>. <p>The time is now <%=Now.TimeOfDay()%></p> <p>The time is now <% response.write(Now.TimeOfDay())%></p> “=“ is shorthand for response.write Server-side comments: <%-- Comments --%> CodeBehind file (Partial class): <%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default2.aspx.vb" Inherits="Default2" %>
ASP.NET Object Model Server Request Object Object Client Server Response Object Application Object Session Object
ASP.NET Request Object When a page is requested, much information is passed along with the request, such as the URL, queryString, and data from a form. The request object allows you to get the information passed along with the request. It is created from the System.Web.HttpRequest class. Demo: testRequest.Htm, TestRequest.aspx
<body> <% response.write ("<h1> cid=" & request.form("cid") & "</h1><br>") response.write ("<h1> cname=" & request.form("cname")& "</h1><br>") Response.Write("<h1> filepath " & Request.FilePath & "</h1><br>") Response.Write("<h1> httpMethod " & Request.HttpMethod & "</h1><br>") Response.Write("<h1> path " & Request.Path & "</h1><br>") Response.Write("<h1> Url " & Request.Url.ToString & "</h1><br>") Response.Write("<h1> urlReferer " & Request.UrlReferrer.ToString & "</h1><br>") Response.Write("<h1> HostName " & Request.UserHostName & "</h1><br>") Response.Write("<h1> HostAddress " & Request.UserHostAddress & "</h1><br>")%> </body> Note: In Request.Form(“cid”), the CID is the Name property of the tetbox, not ID property.
Request Object Collections QueryString http://my.com/Target.htm?CustID=C1&CustName=Chao cid = Request.queryString(“CustID”) cName=Request.queryString(“CustName”) Form A form with two text boxes:CustID, CustName cid = Request.Form(“CustID”) cName=Request.Form(“CustName”) Cookies ClientCertificates Path, ApplicationPath, PhysicalApplicationPath, etc. Demo: testReqForm.htm, testReqForm.aspx
TestReqForm <form method="POST" action="testReqForm.aspx?myquery=testquery"> <p>EnterCID:<input type="text" name="CID" size="20"></p> <p>EnterName:<input type="text" name="CNAME" size="20"></p> <p><input type="checkbox" name="C1" value="ON">checkbox1 <input type="checkbox" name="C2" value="ON">checkbox 2</p> <p><input type="radio" value="V1" checked name="R1">radio1</p> <p><input type="radio" name="R1" value="V2">radio 2</p> <p><select size="1" name="D1"> <option value="A">A</option> <option value="B">B</option> <option value="C">C</option> </select>listbox</p> <p><input type="submit" value="Submit" name="B1"><input type="reset" value="Reset" name="B2"></p> <input type="hidden" name="hidden1" value="Hi, it's me!"> </form>
TestReqForm.Aspx <% response.write ("<h1> cid=" & request.form("cid") & "</h1><br>") response.write ("<h1> cname=" & request.form("cname")& "</h1><br>") response.write ("<h1> hidden variable=" & request.form("hidden1")& "</h1><br>") if request.form("C1")="ON" then response.write ("<h1>You select checkbox 1</H1><br>") end if if request.form("C2")="ON" then response.write ("<h1>You select checkbox 2</H1><br>") if request.form("R1")="V1" then response.write ("<h1>You select Radio 1</H1><br>") else response.write ("<h1>You select Radio 2</H1><br>") response.write ("<h1> listBox=" & request.form("D1")& "</h1><br>") response.write ("<h1>" & request.queryString("myquery")& "</h1><br>") %>
ASP.NET Response Object This object allows you to send information back to client. It is created from the System.Web.HttpResponse class. Properties: Buffer Cookies (a collection) Methods: Response.Write (“…..”) *** MessageBox is not available for web project ***. Response.Clear(), Response.Flush(): clear/flush buffer Response.Redirect (“URL”)
Buffer When ASP.Net is running the code, it gradually builds up the HTML that will be sent back to the browser. As the HTML is generated, it is placed in a buffer. Normally, the HTML is held in the buffer so that it isn’t sent to the browser until the page finishes executing. Response.Buffer: The default value for this property is true which means the page is buffered and sent in one block. Response.Buffer=False sends html as it is generated.
The Application and Session Objects Application state: A central, site-wide store of variables that we can get from any page. A session is a single visit to a web site, and normally includes visits to a number of pages. Each time a visitor comes to your web site, a session object is created for the visitor. Session state is a store of variables that relates to a session.
Examples of Using the Application and Session Objects Examples of session variables are: user’s id, user’s name, Shopping cart, etc. Examples of application variables are: visitor counter.
Working with the Application and Session To place a value into the Application and Session simply assign it a key and then assign the value: Application (“Name”)=“Smith” Session (“Age”)=25 To read values from the Application and Session: Cname=Application(“Name”) myAge = Session(“Age”) To remove an item, or all items: Remove, RemoveAll() Application.Remove(“Name”) Session.RemoveAll()
ApplicationState/SessionState Properties Lock, Unlock SessionState: SessionID TimeOut
The Events of the Application and Session Objects Application_Start Web site start, and the first view Application_End Web site shut down Session_Start Session_End
The Global.ASAX File Eery ASP.NET application has this special script file. Must reside in the web site’s root directory. It can contain script code that belongs to the application, or each session. The event handler of the application and session objects must be placed in the Global.asax file. Note: Website/Add New Item/Global
<%@ import Namespace="System.Data" %> <%@ import Namespace="System.Data.Oledb" %> <script runat="server"> Dim strConn As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\salesDB.mdb" Dim objConn As New OleDbConnection(strConn) Dim strSQL As String Dim objDataReader As OleDbDataReader Dim objComm As New OleDbCommand() Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs) objConn.Open() strSQL = "select VisitorCounter from VCounterTable where CounterDate = (" strSQL = strSQL + "Select Max(CounterDate) from VCounterTable);" Dim objComm As New OleDbCommand(strSQL, objConn) objDataReader = objComm.ExecuteReader() objDataReader.Read() Application("visitor") = objDataReader("VisitorCounter") objConn.Close() End Sub Sub Application_End(ByVal sender As Object, ByVal e As EventArgs) objComm.Connection = objConn objComm.CommandType = CommandType.Text strSQL = "Insert Into VCounterTable Values (#" + CStr(DateTime.Now()) + "#, " + CStr(Application("visitor")) + ");" objComm.CommandText = strSQL objComm.ExecuteNonQuery() Sub Session_Start(ByVal sender As Object, ByVal e As EventArgs) Application.Lock() Application("visitor") = Application("visitor") + 1 Session("visitor") = Application("visitor") Application.UnLock() Sub Session_End(ByVal sender As Object, ByVal e As EventArgs) ' Code that runs when a session ends. End Sub </script>
Web Form vs HTML Form HTML Form: A web page that contains one or more HTML form controls such as textbox, checkbox, dropdown list, and button inside an HTML <form> tag. Web Form: A web page that contains: ASP.NET server controls, and/or HTML form controls inside a <form runat=“server”> tag. ASP.NET code that produces dynamic content to be displayed within the web form.
Web Form Events Every time a page is called the page object goes through a series of stage: initializing, loading, processing and disposing of information. It happens every time a round trip to the server occurs. Page_Init Page_Load: Occurs when a page is visible. Control Events Page_Unload Note: A webform is handled by itself. Demo: web form with regular HTML controls – ASPNET/TestRequestFormHTML.ASPX
ASP.NET Server Controls Intrinsic Controls: These controls correspond to their HTML counterparts. Ex. Textbox, listbox, button, etc. Data-Centric Controls: Controls used for binding and displaying data from a data source, such as the DataGrid control. Rich Controls: Such as Calendar, AdRotator. Validation Controls: Such as RequiredFieldValidator. Namespace:System.Web.UI.Webcontrols
Example of ASP.Net Control Tag Textbox: <asp:TextBox ID="TextBox1" runat="server" Style="z-index: 100; left: 80px; position: absolute; top: 64px"></asp:TextBox> Properties: Control type ID BackColor, ForeColor, Height, Width Runat=“server”
ASP.Net Composite Controls DropdownList: Control tag + ListItem tag <asp:dropdownlist id="list1" runat="server"> <asp:listitem>Apple</asp:listitem> <asp:listitem>Orange</asp:listitem> <asp:listitem>Banana</asp:listitem> </asp:dropdownlist> <asp:listbox/> Demo:TestListBox.aspx <asp:radiobuttonlist/> <asp:checkboxlist/>
Server Control Events Object Browser System.Web.UI.Webcontrols
Postback Postback is the process by which the browser posts information back to the server telling the server to handle the event, the server does so and sends the resulting HTML back to the browser.
The effects of Postback Remember the state of the form by adding a hidden _VIEWSTATE variable. Enable to write event handler. Page.ISPostBack property. IF Not Page.ISPostBack Then This is the first time the page is loaded. Demo: Display welcome message only once.
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load If Not Page.IsPostBack Then Response.Write("Welcome to this demo page") End If End Sub
ASP.Net Controls’ AutoPostBack Property Button always triggers postback. Other controls, by default, this property is set to false.