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Tips, Trick and Techniques for ASP Developers Atlanta ASP User Group

Tips, Trick and Techniques for ASP Developers Atlanta ASP User Group. Don Draper Draper Consulting, Inc. Don@draperconsulting.com http://www.draperconsulting.com. Topics. Transact-SQL Techniques Handling Expired Session Techniques Background Images in Tables JavaScript Tips

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Tips, Trick and Techniques for ASP Developers Atlanta ASP User Group

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  1. Tips, Trick and Techniquesfor ASP DevelopersAtlanta ASP User Group Don Draper Draper Consulting, Inc. Don@draperconsulting.com http://www.draperconsulting.com

  2. Topics • Transact-SQL Techniques • Handling Expired Session Techniques • Background Images in Tables • JavaScript Tips • The Response Object • Understanding HTTP Headers Draper Consulting, Inc. http://www.draperconsulting.com

  3. Transact-SQL Techniques Draper Consulting, Inc. http://www.draperconsulting.com

  4. Transact-SQL, Technique #1Ad-Hoc WHERE Clause • Problem:User can enter any selection criteria in multiple fields for ad-hoc query, but data source is a stored procedure. • Solution:WHERE (col1 = @arg1 OR @arg1 is null) AND (col2 like @arg2 OR @arg2 is null) AND (col3 like @arg3 OR @arg3 is null) Draper Consulting, Inc. http://www.draperconsulting.com

  5. Transact-SQL, Technique #1Ad-Hoc WHERE Clause • In ASP Code… • Make sure empty parameters are passed as nulls if parm = empty then parm = null • Can use Parameter Object Set param1 = cmd.CreateParameter ("city", adVarChar,adParamInput,15,city) Set param2 = cmd.CreateParameter ("company", adVarChar, adParamInput, 40, company) cmd.Parameters.Append param1 cmd.Parameters.Append param1 Draper Consulting, Inc. http://www.draperconsulting.com

  6. Transact-SQL, Technique #1Ad-Hoc WHERE Clause • In ASP Code… • Can use Array function to pass params city = request("city") if city = empty then city = Null ‘ pass null to sp if not needed Set rs = cmd.Execute (recs, Array( company, city ) ) Draper Consulting, Inc. http://www.draperconsulting.com

  7. Transact-SQL, Technique #1Ad-Hoc WHERE Clause • In Stored Procedure… • default arguments to null @companyname varchar(40) = null, … • use “Is null”..NOT “= null” Good: WHERE (company like @company OR @company is null) Bad: WHERE (company like @company OR @company = null) Draper Consulting, Inc. http://www.draperconsulting.com

  8. Transact-SQL, Technique #2Ad-Hoc ORDER BY Clause • Problem:User can click on any header in table and the result set is reordered for that column. However, the data source is a stored procedure. How can I alter ORDER BY clause? Solution #1: Use Exec() • lose precompiled advantage of stored proce • Solution #2: Use ANSI CASE (better) • Retain precompiled advantage of stored proc Draper Consulting, Inc. http://www.draperconsulting.com

  9. Transact-SQL, Technique #2Ad-Hoc ORDER BY Clause • Sample Code for Stored Procedure ORDER BY CASE @sort  passed in a argument to procedure WHEN 'id' THEN CAST (CustomerID as varchar(20)) WHEN 'companyname' THEN companyname WHEN 'city' THEN city ELSE CAST (CustomerID as varchar(20)) END Draper Consulting, Inc. http://www.draperconsulting.com

  10. Handling Expired Sessions Draper Consulting, Inc. http://www.draperconsulting.com

  11. Handling Expired Sessions • We use sessions to … • Maintain state information • Maintain user specific data across pages • Provide additional security…and more • Sessions end by • Session.Abandon • Session expires due to period of inactivity Draper Consulting, Inc. http://www.draperconsulting.com

  12. Handling Expired Sessions • When session expires • Need user to start over • login again • start new session & re-establish session data • Techniques to check for current session • Check for session value at top of page • Let session events handle it for you! Draper Consulting, Inc. http://www.draperconsulting.com

  13. Handling Expired Sessions • Typical Technique: • Check for session variable at the top of each page If session(“userid”) = “” then redirect(“login.asp”) End if Draper Consulting, Inc. http://www.draperconsulting.com

  14. Handling Expired Sessions • Suggested Technique: • Let a session event handle it for you • In Global.ASA file Session_OnStart • Check referring URL • Redirect/Transfer if not coming from your start (login?) page fromURL = Request.ServerVariables("URL") if InStr(lcase(fromURL), "login.asp") = 0 then Response.Redirect("expired_page.asp") end if Draper Consulting, Inc. http://www.draperconsulting.com

  15. Handling Expired Sessions • Watch out for… • login page is ASP page • Session already started before login • Use <@ EnableSessionState = FALSE> • Use Session.Abandon to kill session • other pages that start session before login • Same as above • use NT Performance Monitor to watch session count when testing Draper Consulting, Inc. http://www.draperconsulting.com

  16. Background Images in Tables Draper Consulting, Inc. http://www.draperconsulting.com

  17. Background Images in Tables Table background images offer an easy way to place other elements over an image. Cell can be used for positioning. Draper Consulting, Inc. http://www.draperconsulting.com

  18. Background Images in Tables • Problem:Background images can be defined as an attribute of a TABLE tag. This permits elements such as text, fields and more to be place over an image. However, Netscape renders the image starting in each cell, even if defined at the TABLE level! Draper Consulting, Inc. http://www.draperconsulting.com

  19. Background Images in Tables <TABLE background=“images/myimg.gif”> .. .. </TABLE> Draper Consulting, Inc. http://www.draperconsulting.com

  20. Background Images in Tables Netscape renders the image inside each cell, even if defined at the TABLE level. As you can see, this is not acceptable! Draper Consulting, Inc. http://www.draperconsulting.com

  21. Background Images in Tables • Solution: Use two nested tables • Outer table • gets one empty cell to hold inner table • background attribute defined in Table tag • Inner table • background attribute in Table tag but with empty value ( background=“” ) • Use cells to position elements over image Draper Consulting, Inc. http://www.draperconsulting.com

  22. Client-Side JavaScript Draper Consulting, Inc. http://www.draperconsulting.com

  23. Client-Side JavaScript • Two common uses… • Place cursor in appropriate form field • Client-side form validation • Place cursor in appropriate form field document.formname.fieldname.focus(); <BODY onLoad="document.form1.name.focus();“> Draper Consulting, Inc. http://www.draperconsulting.com

  24. Client-Side JavaScript Place cursor in UID field if empty…otherwise place in password field <script language="JavaScript"> <!-- hide from old browsers function set_focus( ) { if (document.forms[0].as_userid.value.length > 0) document.forms[0].as_password.focus(); else document.forms[0].as_userid.focus(); } // --> </script> Draper Consulting, Inc. http://www.draperconsulting.com

  25. Client-Side JavaScript Use // to comment out closing HTML comments <script language="JavaScript"> <!-- function myfunction( ) { } // -->  the js comment (//) prevents errors in some browsers </script> Draper Consulting, Inc. http://www.draperconsulting.com

  26. Client-Side JavaScript FormChek.js - Form Validation Library • Free, Public Domain Library • Over 60K of validation routines by Eric Krock, NS • Basic data validation routines • Reformat data • Prompt user • Interactively check field contents • Credit card validation Draper Consulting, Inc. http://www.draperconsulting.com

  27. Understanding HTTP Headers Draper Consulting, Inc. http://www.draperconsulting.com

  28. Understanding HTTP Headers? • Request Headers (from browser) • GET - hyperlink request • POST - FORM request (default) • Response Headers (from server or ASP code) • Content-Type: - defines type of content • Location: - redirect browsers to URL • Set-Cookie: - stores data on browser Draper Consulting, Inc. http://www.draperconsulting.com

  29. Request & Response GET URL HTTP/1.0 Pages / ASP FunctionA( ) FunctionB( ) FunctionC(a) .. HTTP Request HTTP Response HTML page or binary content (PDF) prefixed with HTTP Response Headers IIS / ASP (server) Web browser Draper Consulting, Inc. http://www.draperconsulting.com

  30. HTTP Response Headers HTTP/1.0 200 OKServer: Apache/1.1.1Content-Type: text/htmlContent-Length: 31078 HTTP Headers <HTML><BODY> My Web Page! </BODY></HTML> HTML Page Draper Consulting, Inc. http://www.draperconsulting.com

  31. HTTP Header Format • Each header is on its own line with no blank lines between them • The last header is followed by a blank line and then the content Draper Consulting, Inc. http://www.draperconsulting.com

  32. HTTP Headers Headers added by Web Server One blank line separates headers from content HTTP/1.0 200 OKServer: Apache/1.1.1Content-Type: text/htmlContent-Length: text/html Headers you can control <HTML><BODY> My Web Page! </BODY></HTML></BODY> HTML Page Draper Consulting, Inc. http://www.draperconsulting.com

  33. Common HTTP Response Headers • Location: (redirection) • Content-Type: (MIME type of content) • Content-Length: (length of content) • Set-Cookie: (save data on browser) Draper Consulting, Inc. http://www.draperconsulting.com

  34. The Response Object Draper Consulting, Inc. http://www.draperconsulting.com

  35. The Response Object • Collections • Cookies • Properties • Buffer • CacheControl • CharSet • ContentType • Expires • ExpiresAbsolute • IsClientConnected • Status • Methods • AddHeader • AppendToLog • BinaryWrite • Clear • End • Flush • PICS • Redirect • Write Draper Consulting, Inc. http://www.draperconsulting.com

  36. The Response Object • Collections • Properties • Buffer • Methods • AddHeader • Clear • End • Flush • Redirect Draper Consulting, Inc. http://www.draperconsulting.com

  37. Tips for Using Flush and End • Response.Flush • Flush after page titles but before long database queries to increase perception of speed • Output continue to fill buffer after Flush is used • Response.Buffer must be TRUE • Response.End • Stops further output to the browser • Use Clear to remove output prior to End Draper Consulting, Inc. http://www.draperconsulting.com

  38. Tips for Using Clear and Redirect • Response.Clear • Clear page content since the last Flush or Clear; headers are still sent • Useful to display only error message instead of standard page content • Response.Redirect • Sends 302 Object Moved response error • Buffer must be true if content already sent • Don’t need Clear prior to Redirect Draper Consulting, Inc. http://www.draperconsulting.com

  39. Request & ResponseRedirect Requires 2 Round Trips to Server File1.asp Request: GET /file1.asp HTTP/1.0 Redirect(“file2.asp”) Response: 302 Object Moved Location: file2.asp File2.asp Request: GET /file2.asp HTTP/1.0 <HTML> Response: 200 Ok HTTP/1.1 200 OK Server: Microsoft-IIS/4.0 Date: Wed, 16 Feb 2000 10:26:53 GMT Content-Length: 218 Content-Type: text/html IIS / ASP (server) Web browser Draper Consulting, Inc. http://www.draperconsulting.com

  40. Request & ResponseServer.Transfer Requires Only 1 Trip to Server(ASP 3.0) File1.asp Server.Transfer(“File2.ASP”) Request: GET /file1.asp HTTP/1.0 File2.asp <HTML> Server send back different file Response: 200 Ok HTTP/1.1 200 OK Server: Microsoft-IIS/4.0 Date: Wed, 16 Feb 2000 10:26:53 GMT Content-Length: 218 Content-Type: text/html IIS / ASP 3.0 (server) Web browser Draper Consulting, Inc. http://www.draperconsulting.com

  41. More Information • Ostrosoft Internet Tools • http://www.ostrosoft.com • HTTP Protocol and Headers • http://www.w3.org/Protocols/rfc2616/rfc2616.html • FormChek.js • Look in search engines • http://www.draperconsulting.com/downloads/formchek.zip Draper Consulting, Inc. http://www.draperconsulting.com

  42. More Information • Wrox Books • Professional Active Server Pages 2.0 (3.0) • ASP 2.0 (2.1) Programmers Reference • ADO 2.0 (2.5) Programmers Reference • http://www.wrox.com • http://webdev.wrox.co.uk/books/BookList.asp Draper Consulting, Inc. http://www.draperconsulting.com

  43. Questions? Draper Consulting, Inc. http://www.draperconsulting.com

  44. Presentation Survey Results Draper Consulting, Inc. http://www.draperconsulting.com

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