Programming Microsoft SQL Server 2000 with Microsoft Visual Basic .Net - P8

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Programming Microsoft SQL Server 2000 with Microsoft Visual Basic .Net - P8 A t y pical ASP. NET applicat ion will be r un in an env ir onm ent in which m any browsers ar e connect ed t o a single Web serv er or a farm of Web serv er s. For sim plicit y , I discuss t he case of t he single Web ser ver, but t he sam e general principles apply t o a far m of Web ser vers. The asynchr onous nat ure of com m unicat ion bet ween a Web serv er and brow sers facilit at es t he m aint enance of a large num ber of concurr ent br owser sessions w it h a single Web serv er. Each of t hese br owsers can have a differ ent session st at e wit h t he Web serv er. I n ot her words, t he sam e page can show differ ent cont ent s t o differ ent users depending on t he int eract ions of each user w it h t he Web serv er . At t he sam e t im e, a dat abase ser ver can pr ov ide a consist ent set of inform at ion acr oss m ult iple browser sessions. Anot her defining char act er ist ic of Web applicat ions is t hat a Web serv er can serv e pages t o m any differ ent k inds of browsers. Alt hough all browser t ypes r ender HTML code in pages ser ved fr om a Web ser ver, t he r endering isn’t necessarily invariant fr om one brow ser t ype t o t he next . Som e br owsers handle client - side script ing in one language but not anot her . Different browser versions t arget different HTML v ersions ( 3.2 and 4.0 are t wo com m on HTML v ersions) . Som e support absolut e posit ioning, but support isn’t univ ersal for t his feat ure. For differences such as t hose not ed, it ’s not uncom m on for Web applicat ions t o hav e t o “sniff” t he br owser t y pe t o det erm ine it s char act erist ics and t hen send a page t hat is r endered and behav es well on t hat br ow ser. ASP.NET offers a couple of approaches t o handling Web applicat ion dev elopm ent issues. First , ASP.NET can elicit HTML from Web serv ers in an at t em pt t o m inim ize t he im pact of different browser t ypes on t he way t hat a page appears in a browser . Second, ASP.NET has built - in capabilit ies for det ect ing br owser t y pesPlease purchase PDF Split-Merge on www.verypdf.com to remove this watermark. and t heir capabilit ies. Your applicat ions can t ap t hese capabilit ies t o dir ect browsers t o pages t hat are r endered well wit hin t hem . N ot e I t ’s a big drain on lim it ed Web applicat ion developm ent resources t o det ect browsers and prepare m ult iple pages t hat are rendered w ell in different brow sers. As a business em ploy ing t alent ed Web developers, wouldn’t you r at her t hose developers spend t heir t im e cr eat ing m or e useful cont ent in different pages t han creat ing m ult iple copies of a sm aller num ber of less useful pages so as t o opt im ize for differ ent browser s? Because ASP.NET is fr ee wit h t he I I S 5.0 Web server, and t he I nt ernet Ex plorer br owser is free wit h m ost Microsoft pr oduct s and from Microsoft ’s I nt ernet sit e, I recom m end you use t he I nt ernet Explor er browser for your ASP.NET applicat ions. Not e t hat Micr osoft didn’t encourage m e t o m ak e t his st at em ent . I nst ead, I m ak e t he st at em ent on t he basis of m y obser vat ions about how t ax ing it is on organizat ions t o creat e Web solut ions t hat work well wit h m ult iple br owsers. Pa ge s a n d t h e Pa ge Cla ss As indicat ed in Chapt er 8, ASP.NET builds on ASP. For exam ple, Web ser vers can discer n an ASP.NET page based on it s ext ension, .aspx. The ex t ension for an ASP.NET page is t he sam e as t he ext ension of ASP pages w it h an x appended t o it . For exam ple, an ASP.NET page w ill have a nam e lik e m ypage.aspx. Any ASP.NET solut ion can hav e m ult iple pages wit hin it . You can designat e one page as t he st art page for an applicat ion. ( Ther e is no st art up obj ect as t her e is wit h Windows applicat ions.) An ASP.NET solut ion can cont ...