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Response Object
Response.Expires Property
   Syntax:
   Parameters:
   Remarks:
   Examples:
Response.ExpiresAbsolute Property
   Syntax:
   Parameters:
   Remarks: Remarks:
   Examples:

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.Expires Property

Response.Expires property sets the length of the time in minutes that the HTML page can be cached on the browser to calculate the absolute expires date & time according to the date & time on the server for the HTTP Expires header.

Syntax:

Response.Expires [=number]

 Or in an ASP file. Imply

<% Response.Expires = number  %>

Parameters:

number

The parameter "number" is the value of duration time in minute of a page in a cache. The data type of "number" is numbers. A value of negative number means immediate expiration. When the calculated absolute expires date from the supplied value of number exceeds January 18, 2038, IIS server will returns an error.

Remarks:

If the same page is requested by client before the page expires, the cached version will be displayed by the client.

If there are multiple Response.Expires or Response.ExpiresAbsolute  on the same page, the web server will use the shortest time period.

Since the system time on the client may not be the same as the system time on the server, setting the parameter of expires to zero sometime does not have the effect of expiring the response immediately. Therefore setting the parameter of expires to a negavtive number can ensure the expiring of the response immediately.

Examples:

  • Default value with No Response.Expires

    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.Expires with value 10

    ASP script command:

    <% Response.Expires = 10 %>

    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
    Expires: Tue, 31 Jan 2012 15:29:08 GMT:29:08 GMT
    Content-Type: text/html
    Set-Cookie: ASPSESSIONIDPPPP=PPPPPPPP; path=/
    Cache-control: private

  • Response.Expires with value 0

    ASP script command:

    <% Response.Expires = 0 %>

    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
    Expires: Tue, 31 Jan 2012 15:19:08 GMT:19:08 GMT
    Content-Type: text/html
    Set-Cookie: ASPSESSIONIDPPPP=PPPPPPPP; path=/
    Cache-control: private

  • Response.Expires with value -1

    ASP script command:

    <% Response.Expires = -1 %>

    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
    Expires: Tue, 31 Jan 2012 15:18:08 GMT:18:08 GMT
    Content-Type: text/html
    Set-Cookie: ASPSESSIONIDPPPP=PPPPPPPP; path=/
    Cache-control: private

  • Multiple Response.Expires with value 10 and 20

    ASP script command:

    <% Response.Charset = 10 %>
    <% Response.Charset = 20 %> 

    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
    Expires: Tue, 31 Jan 2012 15:29:08 GMT:29:08 GMT
    Content-Type: text/html
    Set-Cookie: ASPSESSIONIDPPPP=PPPPPPPP; path=/
    Cache-control: private

Response.ExpiresAbsolute Property

Response.ExpiresAbsolute property sets the actual  expire date and time that the HTML page can be cached on the browser for the HTTP Expires header.

Syntax:

Response.ExpiresAbsolute [=[date][time]]

 Or in an ASP file. Imply

<% Response.Expires = [date][time]  %>

Parameters:

date

The parameter "date" is the value of expire date of a page in a cache. The data type of "date" is window date format. In general, Date values must be enclosed within pound signs (#) and be in the format M/d/yyyy. But the value sent in the HTTP Expires header will convert to the RFC-1123 date format. If the value of date is not set, the default value of date is the day of the ASP file run. When the absolute expires date from the supplied value of number exceeds January 18, 2038, IIS server will returns an error.

time

The parameter "time" is the value of expire time of a page in a cache. The data type of "time" is window time format. In general, time values must be enclosed within pound signs (#) and be in the format hh:mm:ss. But the value sent in the HTTP Expires header will convert to the RFC-1123 date format with GMT time zone. If the value of time is not set, the default value of time is the midnight of the day of the ASP file run in GMT format.

Remarks: Remarks:

The value of the parameters must be enclosed in pound marks (# #)

If the same page is requested by client before the page expires, the cached version will be displayed by the client.

If there are multiple Response.ExpiresAbsolute or Response.Expires in the same page, the web server will use the shortest time period.

Examples:

  • Default value with No Response.ExpiresAbsolute

    ASP script command:t 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.ExpiresAbsolute with value "February 18, 2012 13:30:15"

    ASP script command:

    <% Response.ExpiresAbsolute = #February 18, 2012 13:30:15# %>

    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
    Expires: Sat, 18 Feb 2012 05:30:14 GMT
    Content-Type: text/html
    Set-Cookie: ASPSESSIONIDPPPP=PPPPPPPP; path=/
    Cache-control: private

  • Response.ExpiresAbsolute with value "February 18, 2012"

    ASP script command

    <% Response.ExpiresAbsolute = #February 18, 2012# %>

    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
    Expires: Fri, 17 Feb 2012 16:00:00 GMT
    Content-Type: text/html
    Set-Cookie: ASPSESSIONIDPPPP=PPPPPPPP; path=/
    Cache-control: private

  • Response.ExpiresAbsolute with value "February 18, 2012 13:30:15"

    ASP script command:

    <% Response.ExpiresAbsolute = #13:30:15# %>

    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
    Expires: Tue, 31 Jan 2012 05:30:14 GMT
    Content-Type: text/html
    Set-Cookie: ASPSESSIONIDPPPP=PPPPPPPP; path=/
    Cache-control: private

  • Multiple Response.ExpiresAbsolute with value "February 18, 2012 13:30:15" and Response.Expires with value 10

    ASP script command:

    <% Response.Charset = 10 %>
    <% Response.ExpiresAbsolute = #February 18, 2012 13:30:15# %>  

    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
    Expires: Tue, 31 Jan 2012 15:29:08 GMT
    Content-Type: text/html text/html
    Set-Cookie: ASPSESSIONIDPPPP=PPPPPPPP; path=/
    Cache-control: private


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ID: 120200002 Last Updated: 1/2/2012 Revision: 0 Ref:

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References

  1. Active Server Pages,  
  2. ASP Overview,  
  3. ASP Best Practices,  
  4. ASP Built-in Objects,  
  5. Response Object,  
  6. Request Object,  
  7. Server Object (IIS),  
  8. Application Object (IIS),  
  9. Session Object (IIS),  
  10. ASPError Object,  
  11. ObjectContext Object (IIS),  
  12. Debugging Global.asa Files,  
  13. How to: Debug Global.asa files,  
  14. Calling COM Components from ASP Pages,  
  15. IIS ASP Scripting Reference,  
  16. ASP Keywords,  
  17. Creating Simple ASP Pages,  
  18. Including Files in ASP Applications,  
  19. ASP Overview,  
  20. FileSystemObject Object,  
  21. http://msdn.microsoft.com/en-us/library/windows/desktop/ms675944(v=vs.85).aspx,  
  22. ADO Fundamentals,  
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