Programming Microsoft SQL Server 2000 with Microsoft Visual Basic .Net - P12

Tham khảo tài liệu programming microsoft sql server 2000 with microsoft visual basic .net - p12, công nghệ thông tin, cơ sở dữ liệu phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả
Nội dung trích xuất từ tài liệu:
Programming Microsoft SQL Server 2000 with Microsoft Visual Basic .Net - P12For m 2 r eappears aft er t he user replies t o t he prom pt , t he formshows t he fir st t wo t ext boxes wit h t heir prior v alues as well as t hefourt h t ex t box for display ing a colum n value. The specific value int he bot t om t ext box is t he one m at ching r ow specified by t he user’sreply t o t he prom pt .Figu re 1 3 - 1 1 . Th e clien t a pp lica t ion form for t h e Se rvice 1 W e b ser vice in t h e Ta b leProce ssor folde r .The processing of t he r et ur n values fr om t he Colum nValues Webm et hod illust r at es a t ypical scenar io. A developer engineer s anapplicat ion so t hat it can accom m odat e any of several scenarios. Forexam ple, a client applicat ion m akes a select ion from t he t ot al set ofcolum n values t o show t he colum n value for j ust one r ow inst ead oft he whole set of colum n values as in Figure 13- 10. Figur e 13- 12t r acks t he pr ocess fr om designat ing database and t able nam es t ocapt uring t he r eply t o t he I nput Box prom pt t o showing t he specificcolum n value t hat a user want s t o v iew. I n t he t op window, t he userdesignat es t hat t hey w ant result s fr om t he Cust om ers t able in t heNor t hwind dat abase before click ing t he but t on labeled Get Colum nValue. The m iddle window shows t he user indicat ed t hat t heapplicat ion should show t he colum n value for t he fift h row. By t heway, t he prom pt adj ust s aut om at ically t o show t he m axim umnum ber of r ows. The applicat ion does t his by r unning t he RowCountWeb m et hod when pr ocessing a request t o show a specific r owvalue fr om t he fir st colum n. The bot t om window in t he figurerev eals BERGS as t he colum n v alue for t he fift h row in t he fir stcolum n. You can easily confirm t his out com e for yourself byexam ining t he out put in Figur e 13- 10, which shows all t he colum nvalues for t he fir st colum n in t he Cust om ers t able from t heNor t hwind dat abase. Figu re 1 3 - 1 2 . Th e clien t applica t ion for t h e Se rvice 1 W e b ser vice in t h eTab le Pr oce ssor folde r de m on st ra t ing h ow it h a nd le s a re qu e st t o sh ow a pa r t icu la r colu m n va lu e from t h e first colu m n of t h e Cu st om e rs t a ble in t h e N or t h w in d d at a ba se .The following list ing shows t he code behind For m 2 t hat m anagest he behavior of t he client applicat ion for t he Web service in t heTableProcessor folder . The list ing st ar t s wit h t he inst ant iat ion of am odule- lev el v ar iable, x ws1, for t he proxy Web serv ice. Not ice howVisual Basic .NET sy st em at ically nam es t he second- level referencein t he pr oxy obj ect . The proxy for t he first Web service useslocalhost as it s second nam e. The proxy for t he deployed ver sionused localhost 1 as it s second nam e. This pr oxy variable, which ist he t hird one in t he chapt er, has localhost 2 as it s second nam e. I nall t hr ee cases, t he fir st nam e for a pr oxy denot es t he clientapplicat ion’s pr oj ect — nam ely, XMLWebSer viceClient s. Also, t henam e for t he prox y obj ect in each case r efer s t o t he .asm x file int he Web service, which has t he nam e Service1 in all t hr eeinst ances.The body of t he list ing includes t hr ee event pr ocedures. One is aform Load event procedure. This ev ent pr ocedure m erely readiest he init ial look of t he for m . I n part icular , it m akes t he t hird andfourt h t ex t boxes, along wit h t heir m at ching labels, invisible. Theapplicat ion also includes a Click event procedure for each but t on ont he form . These event procedur es inv oke t he RowCount andColum nValues Web m et hods as well as processing t heir r et urnvalues. As you can see, t he x ws1 pr oxy variable appear s in bot hClick event procedur es, which is why t he list ing st art s byinst ant iat ing t he v ariable at t he m odule level.The But t on1_Click event procedur e inv ok es t he RowCount Webm et hod and displays it s result in Text Box3. This pr ocedure act uallyst ar t s by m ak ing sure Text Box4 and it s m at ching label are invisible.These t wo cont rols are for displaying a colum n v alue and labelingt he ret ur n value, but a click of t he Row Count but t on ( But t on1)doesn’t show any colum n values. Nex t t he procedure copies t heTex t pr opert y v alues of Text Box1 and Text Box2 t o m em oryvar iables in t he client applicat ion. These variables st ore t he nam e oft he dat abase and t he t able for t he Web serv ice t o ex am ine. Aft ersaving t he local m em or y v ariables, t he pr ocedure uses t hem asargum ent s while invoking t he RowCount Web m et hod. Theargum ent s specify for which t able in which dat abase t o ret ur n a r owcount . The final group of lines in t he ev ent ...