Response Object

Another important function of Response object is the output of HTTP headers to the client. As part of the HTTP header, these types of response objects should be sent before sending any body content to the client.

Response.ContentType Property

Response.ContentType sets the value of content-type header to specify the content type of the HTTP response .

Syntax:

Response.ContentType [=Content Type]

 Or in an ASP file. Imply

<% Response.Charset = Content Type %>

Parameters:

Content Type

The parameter "Content Type" is the value of the content-type header. The data type of "Content Type" is strings of format "type/subtype" and the value must be enclosed in quotation marks (" "). "type" is the general content category and "subtype" is the specific content type. The possible values of "Content Type" are

Type	Type/Subtype
text : textual information	text/plain : textual data
	text/html : HTML
	text/css : Cascading Style Sheets
	text/xml : Extensible Markup Language
image : image data	image/gif : GIF image
	image/jpeg : JPEG image
	image/png : Portable Network Graphics
	image/tiff : Tag Image File Format
	image/svg+xml : SVG vector image
audio : audio data	audio/mp4 : MP4 audio
	audio/mpeg : MP3 audio
	audio/ogg : Ogg
video : video data	video/mpeg : MPEG-1
	video/mp4 : MP4
	video/quicktime : QuickTime video
	video/ogg : Ogg video
application : processed data	application/pdf : Portable Document Format
	application/xhtml+xml : XHTML

Remarks:

In general, the default value of the Content Type parameter is "text/html" if there is  Content Type property is not set for the page.

Since each page can only be assigned to one Content Type, the last instance of Response.ContentType in the HTTP header setting of a ASP file will replace all previous Response.ContentType Setting.

If the response buffering is not enbled, the ContentType header setting must be set before any response is sent to the client.

Examples:

• Default value with No Response.ContentType propertye property

  ASP script command:

  <%  %>

  HTTP header response:

  HTTP/1.1 200 OK
  Server: Microsoft-IIS/5.1
  Date: Tue, 31 Jan 2012 15:19:08 GMT
  X-Powered-By: ASP.NET
  Content-Length: 0
  Content-Type: text/html
  Set-Cookie: ASPSESSIONIDPPPP=PPPPPPPP; path=/
  Cache-control: private

• Response.ContentType with value "image/jpeg"

  ASP script command:

  <% Response.Charset = "image/jpeg" %>

  HTTP header response: 

  HTTP/1.1 200 OK
  Server: Microsoft-IIS/5.1
  Date: Tue, 31 Jan 2012 15:19:08 GMT
  X-Powered-By: ASP.NET
  Content-Length: 0
  Content-Type: image/jpeg
  Set-Cookie: ASPSESSIONIDPPPP=PPPPPPPP; path=/
  Cache-control: private

• Multi Response.Charset with value "image/jpeg" and "text/html"

  ASP script command:

  <% Response.Charset = "image/jpeg" %>
  <% Response.ContentType = "text/html" %> 

  HTTP header response: response: 

  HTTP/1.1 200 OK
  Server: Microsoft-IIS/5.1
  Date: Tue, 31 Jan 2012 15:19:08 GMT
  X-Powered-By: ASP.NET
  Content-Length: 0
  Content-Type: text/html
  Set-Cookie: ASPSESSIONIDPPPP=PPPPPPPP; path=/PPP; path=/
  Cache-control: private

Response.Charset Property

Response.Charset property appends the name of character set to the charset parameter in the content-type header to specify the character encoding of the response contents for the browser.

Syntax:

Response.Charset (CharsetName)

 Or in an ASP file. Imply

<% Response.Charset = CharsetName  %>

Parameters:

CharsetName

The parameter "CharsetName" is the value of the Character set name appended to the charset parameter of the content-type header. The data type of "CharsetName" is strings and the value must be enclosed in quotation marks (" "). The possible values of "CharsetName" are

Remarks:

Response.Charset property only appends the specified value to the charset parameter of the content-type header. There is no mechanism to validate whether the specified value represents a valid character set. And there is no browser can understand all character set.

Since each page can only be encoded in one charset, the last instance of Response.Charset in the HTTP header setting of a ASP file will replace all previous Response.charset Setting.

If the response buffering is not enbled, the Charset header setting must be set before any response is sent to the client.

The Unicode encoding, UTF-8 is one of the widely used charset to represent Unicode text in page with mixed languages

Besides, the value of CharsetName and value of codepage should match with each other. Since the code page is the value to specify the encoding code page used by the web server to general the response contents, while the character set is the value to specify the decoding character set used by the page browser. Therefore, a codepage setting, by Response.CodePage, Session.CodePage, @CodePage, or AspCodePage, is needed to ensure the readability of the displayed text. And a charsetname setting should also be used to ensure the decoding character set used in client browser match with the encoding code page used in the web server.web server.

Name of Character set can refer to http://www.iana.org/assignments/character-sets

Examples:

• Default value with No Response.Charset property

  ASP script command:

  <%  %>

  HTTP header response:

  HTTP/1.1 200 OK
  Server: Microsoft-IIS/5.1
  Date: Tue, 31 Jan 2012 15:19:08 GMT
  X-Powered-By: ASP.NET
  Content-Length: 0
  Content-Type: text/html
  Set-Cookie: ASPSESSIONIDPPPP=PPPPPPPP; path=/
  Cache-control: private

• Response.Charset with value "UTF-8"

  ASP script command:

  <% Response.Charset = "UTF-8" %>

  HTTP header response: 

  HTTP/1.1 200 OK
  Server: Microsoft-IIS/5.1
  Date: Tue, 31 Jan 2012 15:19:08 GMT
  X-Powered-By: ASP.NET
  Content-Length: 0
  Content-Type: text/html; Charset=UTF-8
  Set-Cookie: ASPSESSIONIDPPPP=PPPPPPPP; path=/
  Cache-control: private

• Multiple Response.Charset with value "UTF-8" and "Big5"

  ASP script command:pt command:

  <% Response.Charset = "UTF-8" %>
  <% Response.Charset = "Big5" %> 

  HTTP header response: 

  HTTP/1.1 200 OK
  Server: Microsoft-IIS/5.1
  Date: Tue, 31 Jan 2012 15:19:08 GMT
  X-Powered-By: ASP.NET
  Content-Length: 0
  Content-Type: text/html; Charset=Big5
  Set-Cookie: ASPSESSIONIDPPPP=PPPPPPPP; path=/
  Cache-control: private