ASP.NET - Server Side

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We have studied the page life cycle and how a page contains various controls. The page itself is instantiated as a control object. All web forms are basically instances of the ASP.NET Page class. The page class has the following extremely useful properties that correspond to intrinsic objects:

  • Session
  • Application
  • Cache
  • Request
  • Response
  • Server
  • User
  • Trace

We will discuss each of these objects in due time. In this tutorial we will explore the Server object, the Request object, and the Response object.

Server Object

The Server object in Asp.NET is an instance of the System.Web.HttpServerUtility class. The HttpServerUtility class provides numerous properties and methods to perform various jobs.

Properties and Methods of the Server object

The methods and properties of the HttpServerUtility class are exposed through the intrinsic Server object provided by ASP.NET.

The following table provides a list of the properties:

Property Description
MachineName Name of server computer
ScriptTimeOut Gets and sets the request time-out value in seconds.

The following table provides a list of some important methods:

Method Description
CreateObject(String) Creates an instance of the COM object identified by its ProgID (Programmatic ID).
CreateObject(Type) Creates an instance of the COM object identified by its Type.
Equals(Object) Determines whether the specified Object is equal to the current Object.
Execute(String) Executes the handler for the specified virtual path in the context of the current request.
Execute(String, Boolean) Executes the handler for the specified virtual path in the context of the current request and specifies whether to clear the QueryString and Form collections.
GetLastError Returns the previous exception.
GetType Gets the Type of the current instance.
HtmlEncode Changes an ordinary string into a string with legal HTML characters.
HtmlDecode Converts an Html string into an ordinary string.
ToString Returns a String that represents the current Object.
Transfer(String) For the current request, terminates execution of the current page and starts execution of a new page by using the specified URL path of the page.
UrlDecode Converts an URL string into an ordinary string.
UrlEncodeToken Works same as UrlEncode, but on a byte array that contains Base64-encoded data.
UrlDecodeToken Works same as UrlDecode, but on a byte array that contains Base64-encoded data.
MapPath Return the physical path that corresponds to a specified virtual file path on the server.
Transfer Transfers execution to another web page in the current application.

Request Object

The request object is an instance of the System.Web.HttpRequest class. It represents the values and properties of the HTTP request that makes the page loading into the browser.

The information presented by this object is wrapped by the higher level abstractions (the web control model). However, this object helps in checking some information such as the client browser and cookies.

Properties and Methods of the Request Object

The following table provides some noteworthy properties of the Request object:

Property Description
AcceptTypes Gets a string array of client-supported MIME accept types.
ApplicationPath Gets the ASP.NET application's virtual application root path on the server.
Browser Gets or sets information about the requesting client's browser capabilities.
ContentEncoding Gets or sets the character set of the entity-body.
ContentLength Specifies the length, in bytes, of content sent by the client.
ContentType Gets or sets the MIME content type of the incoming request.
Cookies Gets a collection of cookies sent by the client.
FilePath Gets the virtual path of the current request.
Files Gets the collection of files uploaded by the client, in multipart MIME format.
Form Gets a collection of form variables.
Headers Gets a collection of HTTP headers.
HttpMethod Gets the HTTP data transfer method (such as GET, POST, or HEAD) used by the client.
InputStream Gets the contents of the incoming HTTP entity body.
IsSecureConnection Gets a value indicating whether the HTTP connection uses secure sockets (that is, HTTPS).
QueryString Gets the collection of HTTP query string variables.
RawUrl Gets the raw URL of the current request.
RequestType Gets or sets the HTTP data transfer method (GET or POST) used by the client.
ServerVariables Gets a collection of Web server variables.
TotalBytes Gets the number of bytes in the current input stream.
Url Gets information about the URL of the current request.
UrlReferrer Gets information about the URL of the client's previous request that is linked to the current URL.
UserAgent Gets the raw user agent string of the client browser.
UserHostAddress Gets the IP host address of the remote client.
UserHostName Gets the DNS name of the remote client.
UserLanguages Gets a sorted string array of client language preferences.

The following table provides a list of some important methods:

Method Description
BinaryRead Performs a binary read of a specified number of bytes from the current input stream.
Equals(Object) Determines whether the specified object is equal to the current object. (Inherited from object.)
GetType Gets the Type of the current instance.
MapImageCoordinates Maps an incoming image-field form parameter to appropriate x-coordinate and y-coordinate values.
MapPath(String) Maps the specified virtual path to a physical path.
SaveAs Saves an HTTP request to disk.
ToString Returns a String that represents the current object.
ValidateInput Causes validation to occur for the collections accessed through the Cookies, Form, and QueryString properties.

Response Object

The Response object represents the server's response to the client request. It is an instance of the System.Web.HttpResponse class.

In ASP.NET, the response object does not play any vital role in sending HTML text to the client, because the server-side controls have nested, object oriented methods for rendering themselves.

However, the HttpResponse object still provides some important functionalities, like the cookie feature and the Redirect() method. The Response.Redirect() method allows transferring the user to another page, inside as well as outside the application. It requires a round trip.

Properties and Methods of the Response Object

The following table provides some noteworthy properties of the Response object:

PropertyDescription
Buffer Gets or sets a value indicating whether to buffer the output and send it after the complete response is finished processing.
BufferOutput Gets or sets a value indicating whether to buffer the output and send it after the complete page is finished processing.
Charset Gets or sets the HTTP character set of the output stream.
ContentEncoding Gets or sets the HTTP character set of the output stream.
ContentType Gets or sets the HTTP MIME type of the output stream.
Cookies Gets the response cookie collection.
Expires Gets or sets the number of minutes before a page cached on a browser expires.
ExpiresAbsolute Gets or sets the absolute date and time at which to remove cached information from the cache.
HeaderEncoding Gets or sets an encoding object that represents the encoding for the current header output stream.
Headers Gets the collection of response headers.
IsClientConnected Gets a value indicating whether the client is still connected to the server.
Output Enables output of text to the outgoing HTTP response stream.
OutputStream Enables binary output to the outgoing HTTP content body.
RedirectLocation Gets or sets the value of the Http Location header.
Status Sets the status line that is returned to the client.
StatusCode Gets or sets the HTTP status code of the output returned to the client.
StatusDescription Gets or sets the HTTP status string of the output returned to the client.
SubStatusCode Gets or sets a value qualifying the status code of the response.
SuppressContent Gets or sets a value indicating whether to send HTTP content to the client.

The following table provides a list of some important methods:

Method Description
AddHeader Adds an HTTP header to the output stream. AddHeader is provided for compatibility with earlier versions of ASP.
AppendCookie Infrastructure adds an HTTP cookie to the intrinsic cookie collection.
AppendHeader Adds an HTTP header to the output stream.
AppendToLog Adds custom log information to the InterNET Information Services (IIS) log file.
BinaryWrite Writes a string of binary characters to the HTTP output stream.
ClearContent Clears all content output from the buffer stream.
Close Closes the socket connection to a client.
End Sends all currently buffered output to the client, stops execution of the page, and raises the EndRequest event.
Equals(Object) Determines whether the specified object is equal to the current object.
Flush Sends all currently buffered output to the client.
GetType Gets the Type of the current instance.
Pics Appends a HTTP PICS-Label header to the output stream.
Redirect(String) Redirects a request to a new URL and specifies the new URL.
Redirect(String, Boolean) Redirects a client to a new URL. Specifies the new URL and whether execution of the current page should terminate.
SetCookie Updates an existing cookie in the cookie collection.
ToString Returns a String that represents the current Object.
TransmitFile(String) Writes the specified file directly to an HTTP response output stream, without buffering it in memory.
Write(Char) Writes a character to an HTTP response output stream.
Write(Object) Writes an object to an HTTP response stream.
Write(String) Writes a string to an HTTP response output stream.
WriteFile(String) Writes the contents of the specified file directly to an HTTP response output stream as a file block.
WriteFile(String, Boolean) Writes the contents of the specified file directly to an HTTP response output stream as a memory block.

Example

The following simple example has a text box control where the user can enter name, a button to send the information to the server, and a label control to display the URL of the client computer.

The content file:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" 
   Inherits="server_side._Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
   "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >

   <head runat="server">
      <title>Untitled Page</title>
   </head>
   
   <body>
      <form id="form1" runat="server">
         <div>
            
            Enter your name:
            <br />
            <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
            <asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Submit" />
            <br />
            <asp:Label ID="Label1" runat="server"/>

         </div>
      </form>
   </body>
   
</html>

The code behind Button1_Click:

protected void Button1_Click(object sender, EventArgs e) {

   if (!String.IsNullOrEmpty(TextBox1.Text)) {
   
      // Access the HttpServerUtility methods through
      // the intrinsic Server object.
      Label1.Text = "Welcome, " + Server.HtmlEncode(TextBox1.Text) + ". <br/> The url is " + Server.UrlEncode(Request.Url.ToString())
   }
}

Run the page to see the following result:

ASP.NET Server Side
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