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ASP.NET Architecture: 

ASP.NET Architecture ASP.NET uses the CLR to replace the existing ISAPI/ASP infrastructure of IIS with a more efficient and easier-to-use framework for servicing HTTP requests. At the same time, ASP.NET provides its own framework for compilation, execution, and building user interfaces.


Evolution On one hand, ASP.NET is an evolution of the ASP programming model Still provides the same intrinsic objects Still can mix script and html Some ASP code can be ported with no changes ASP.NET supports any .NET language Pages use .aspx extension to distinguish from .asp pages


Revolution ASP.NET is more than just ASP 4.0 Pages are compiled into assemblies improving performance and diagnostics Code-behind encourages better separation of code from HTML Extensible, server-side control architecture Server-side data binding model Form validation architecture Web Services allow Assemblies to expose themselves as SOAP servers

Page Compilation: 

Page Compilation Every ASP.NET page is compiled into an assembly on first access It is compiled into an assembly containing a single class that derives from System.Web.UI.Page The name for the Page-derived class is the file name of the page, replacing the '.' with a '_' (like foo_aspx) Any static HTML along with any interspersed code is rendered in the Render function of a single control embedded in the page The generated assembly is stored in the CodeGen directory on the server machine


ASP.NET Page Compilation

ASP.NET Compilation model: 

ASP.NET Compilation model ASP.NET compiles code on demand based on source code dependencies (much like NMAKE) ASP.NET compiles .ASPX files once and caches the resultant DLL If source file(s) newer than cached DLL, a new compilation takes place and the new DLL is cached If source file(s) not newer than cached DLL, the cached DLL is used Shadow-copies of the DLLs are used to allow existing requests to be processed using the "old" code


System.Web.UI.Page The Page class provides facilities for rendering HTML Response and Request objects are available as properties of the class Methods for rendering are provided Events associated with generating the page are defined


class Page : TemplateControl, IHttpHandler { // State management public HttpApplicationState Application {get;} public HttpSessionState Session {virtual get;} public Cache Cache {get;} // Intrinsics public HttpRequest Request {get;} public HttpResponse Response {get;} public HttpServerUtility Server{get;} public string MapPath(string virtualPath); public void Navigate(string url); // Client information public ClientTarget ClientTarget {get; set;} public bool IsUplevel {virtual get;} public IPrincipal User {get;} //... } System.Web.UI.Page


class Page : TemplateControl, IHttpHandler { // Core public UserControl LoadControl(string virtualPath); public ControlCollection Controls {virtual get;} public string ID {virtual get; virtual set;} public bool IsPostBack {get;} protected virtual void Render(HtmlTextWriter writer); // Events public event EventHandler Init; public event EventHandler Load; public event EventHandler PreRender; public event EventHandler Unload; //... } System.Web.UI.Page


<%@ Page Language="C#" %> <html><body><head><script language="C#" runat=server> private ArrayList m_values = new ArrayList(); void Page_Load(Object sender, EventArgs e) { if (!Page.IsPostBack) { m_values.Add("v1"); m_values.Add("v2"); m_values.Add("v3"); m_values.Add("v4"); } } </script> </head> <h2>My test page</h2> <%if (IsUplevel) { Response.Write("<div style=\"width:100%; filter:"); Response.Write("progid:DXImageTransform.Microsoft."); Response.Write("Wheel(duration=3);\">"); Response.Write("My page array has:</div>"); } else Response.Write("<div>My page array has:</div>"); %> <br/><ul> <% for (int i=0; i<m_values.Count; i++) Response.Write("<li>" + m_values[i] + "</li>"); %> </ul> </body> </html> Sample aspx file customizing Page

Code Behind: 

Code Behind In addition to customizing the generated Page class using embedded code, ASP.NET supports page inheritance Technique of Page inheritance is called code-behind Supported through the Inherits attribute of the Page directive Promotes separation of code and presentation Code-behind files can either be pre-compiled, or compiled on demand using the src attribute of the Page directive


Sample aspx file with code behind <%@ Page Language="C#" src="SamplePage.cs" Inherits="DM.AspDotNet.MyPage" %> <html> <body> <h2>My test page</h2> <% WriteTitle(); %> <br/> <% WriteArray(); %> </body> </html>


Sample code-behind file – SamplePage.cs using System; using System.Web.UI; using System.Collections; namespace DM.AspDotNet { public class MyPage : Page { private ArrayList m_values = new ArrayList(); protected void Page_Load(Object sender, EventArgs e) { if (!Page.IsPostBack) { m_values.Add("v1"); m_values.Add("v2"); m_values.Add("v3"); m_values.Add("v4"); } } public void WriteTitle() { if (IsUplevel) { Response.Write("<div style=\"width:100%; filter:"); Response.Write("progid:DXImageTransform."); Response.Write("Microsoft.Wheel(duration=3);\">"); Response.Write("My page array has the following values:</div>"); } else Response.Write("<div>My page array has the following values:</div>"); } public void WriteArray() { Response.Write("<ul>"); for (int i=0; i<m_values.Count; i++) Response.Write("<li>" + m_values[i] + "</li>"); Response.Write("</ul>"); } } }

ASP.NET Directives: 

ASP.NET Directives ASP.NET supports a variety of directives to control compilation and linkage All assemblies in the bin subdirectory are automatically referenced csc.exe /r command-line parameter exposed via @Assembly directive C# using statement exposed via @Import directive Several techniques available for referencing secondary source files


ASP.NET Directives


@page Directives

Server-side controls: 

Server-side controls Web application development has always involved extracting values from query strings and form data. ASP.NET provides a more traditional application development model through server-side controls.

Traditional HTML generation: 

Traditional HTML generation Traditional ASP development involves explicitly generating client-side HTML Server-side script writes directly to intrinsic Response object Database queries must be turned into HTML elements Form contents must be explicitly queried through Request object Provided little more than server-side printf functionality


Figure 3.1: Traditional ASP page <%@ Language="javascript" %> <html><body> <form> <h3>Enter name: <input name="Name" type=text value="<%=Request("Name") %>"></input> Personality: <select name="Personality"> <option <% if (Request("Personality") == "extraverted") { Response.Write("selected"); }%> >extraverted </option> <option <% if (Request("Personality") == "introverted") { Response.Write("selected"); }%> >introverted </option> <option <% if (Request("Personality") == "in-between") { Response.Write("selected"); }%> >in-between </option> </select> <input type=submit name="Lookup" value="Lookup"></input> <p> <% if (Request("Name") != "") { %> Hi <%=Request("Name") %>, you selected <%=Request("Personality") %> <% } %> </p> </form></body></html>

ASP.NET server side controls: 

ASP.NET server side controls ASP.NET defines server side controls to abstract HTML generation process Server side controls retain state between post-backs Server side controls issue events on the server Server side controls generate appropriate HTML to client


<%@ Page Language="C#" %> <html> <body> <form runat=server> <h3>Enter name: <input ID="txtName" type=text runat=server/> Personality: <select ID="Personality" runat=server> <option>extraverted</option> <option>introverted</option> <option>in-between</option> </select> <input type=submit value="Submit"/> <p> <% if (IsPostBack) {%> Hi <%=txtName.Value%>, you selected <%=Personality.Value%> <% } %> </p> </form> </body> </html> Figure 3.2: ASP.NET page using server-side controls


Figure 3.3: HTML generated by server side controls <html> <body> <form name="ctrl1" method="post" action="ServerSideCtrls.aspx" id="ctrl1"> <input type="hidden" name="__VIEWSTATE" value="YTB6MTY0MDA4NTc2Ml9fX3g=a7d02a14" /> <h3>Enter name: <input name="txtName" id="txtName" type="text" value="Joe" /> Personality: <select name="Personality" id="Personality"> <option value="extraverted">extraverted</option> <option selected value="introverted">introverted</option> <option value="in-between">in-between</option> </select> <input type=submit value="Submit"/> <p> Hi Joe, you selected introverted </p> </form> </body> </html>

Server-side events: 

Server-side events In addition to retaining state, server-side controls can issue events Many events traditionally generated on the client-side can be propagated to the server Primarily 'click' and 'change' events are available Warning: every server-side event generates a post-back round trip


<%@ Page Language="C#" %> <html> <head> <script runat=server> void WriteGreeting(Object sender, EventArgs E) { Greeting.InnerText = "Hi " + txtName.Value + ", you selcted " + Personality.Value; } </script> </head> <body> <form runat=server> <h3>Enter name: <input ID="txtName" type=text runat=server/> Personality: <select ID="Personality" runat=server> <option>extraverted</option> <option>introverted</option> <option>in-between</option> </select> <input type=button value="Submit" runat=server OnServerClick="WriteGreeting" /> <div id="Greeting" runat=server /> </form> </body> </html> Figure 3.4: Using server-side events


Figure 3.5: HTML generated using server-side events <html> <body> <form name="ctrl2" method="post" action="ServerSideEvents.aspx" id="ctrl2"> <input type="hidden" name="__EVENTTARGET" value="" /> <input type="hidden" name="__EVENTARGUMENT" value="" /> <input type="hidden" name="__VIEWSTATE" value="YTB6..." /> <script language="javascript"> function __doPostBack(eventTarget, eventArgument) { var theform = document.ctrl2 theform.__EVENTTARGET.value = eventTarget theform.__EVENTARGUMENT.value = eventArgument theform.submit() } </script> <h3>Enter name: <input name="txtName" id="txtName" type="text" value="Joe" /> Personality: <select name="Personality" id="Personality"> <option value="extraverted">extraverted</option> <option value="introverted">introverted</option> <option selected value="in-between">in-between</option> </select> <input name="ctrl7" type="button" value="Submit" / onclick="javascript:__doPostBack('ctrl7','')"> <div id="Greeting">Hi Joe, you selected in-between</div> </form></body></html>


Controls ASP.NET provides two sets of server controls. HtmlControls that use the same names and syntax as their HTML counterparts, and WebControls which provide a more consistent programming model and a higher level of abstraction.


HtmlControls HtmlControls are server-side representations of standard HTML elements Any HTML element in an ASPX page marked with the runat=server attribute will become an HTML control on the server All derive from HtmlControl class HTML elements with no distinguished server-side functionality (like div, span, etc.) are all represented as HtmlGenericControl instances


Figure 3.6: Hierarchy of HtmlControls and the tags they map to


WebControls WebControls provide a more consistent object model and a higher level of abstraction than HtmlControls Most HTML elements can also be represented as WebControls on the server WebControl versions typically have a more consistent interface (background color is always BackColor property whereas in HTML it may be a style attribute (span) or a property (table) ) WebControls also provide higher-level controls with more functionality than primitive HTML elements (like the Calendar control) WebControls may render themselves differently based on client browser capabilities


Figure 3.7: Hierarchy of WebControls


<%@ Page Language="C#" %> <html> <body> <form runat=server> <input type=radio runat=server>click me</input><br/> <input type=checkbox runat=server>check me</input><br/> <input type=button value="Push me" runat=server /><br/> <input type=text value="type in me" runat=server /><br/> <textarea value="type more in me" runat=server /><br/> <table runat=server> <tr><td>cell00</td><td>cell01</td></tr> <tr><td>cell10</td><td>cell11</td></tr> </table> </form> </body> </html> Figure 3.9: A sample ASP.NET page written with HtmlControls


<%@ Page Language="C#" %> <html> <body> <form runat=server> <asp:RadioButton Text="click me" runat=server/><br/> <asp:CheckBox Text="check me" runat=server/><br/> <asp:Button Text="Push me" runat=server /><br/> <asp:TextBox Text="type in me" runat=server /><br/> <asp:TextBox TextMode=MultiLine rows=3 Text="type more in me" runat=server /><br/> <asp:Table runat=server> <asp:TableRow> <asp:TableCell>cell00</asp:TableCell> <asp:TableCell>cell01</asp:TableCell> </asp:TableRow> <asp:TableRow> <asp:TableCell>cell10</asp:TableCell> <asp:TableCell>cell11</asp:TableCell> </asp:TableRow> </asp:Table> </form> </body> </html> Figure 3.8: A sample ASP.NET page written with WebControls


Summary ASP.NET is a significant departure from classic ASP All pages in ASP.NET are compiled assemblies Pages are rendered by iteratively rendering all controls within them Directives in ASP.NET control page compilation, assembly references, namespace usage, and output caching, among other things Server-side controls retain state between post-backs Server-side controls can issue events on the server HtmlControls provide server-side equivalents of HTML elements WebControls provide more consistent object model for server-side controls, as well as some more sophisticated controls



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