techtips8 面向VisualBasic程序员的杂志 第8版.docx

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1、WelcometotheEighthEditionoftheVBPJTechnicalTipsSupplement!ThesetipsandtricksweresubmittedbyprofessionaldevelopersusingVisualBasic3.0,VisualBasic4.0,VisualBasic5.0,VisualBasic6.0,VisualBasicforApplications(VBA),andVisualBasicScript(VBS).TheeditorsatVisualBasicProgrammer,sJournalcompiledthetips.Instea

2、doftypingthecodepublishedhere,downloadthetipsfromthefree,Registered1.evelofTheDevelopmentExchangeat.Ifyou,dliketosubmitatiptoVisualBasicProgrammer,sJournal,pleasesendittoUserTips,FawcetteTechnicalPublications,209HamiltonAve.,PaloAlto,California,USA,94301-2500.Youcanalsofaxitto650-853-0230orsenditele

3、ctronicallytovbpjedit.Pleaseincludeaclearexplanationofwhatthetechniquedoesandwhyit,suseful,andindicateifit,sforVBA,VBS,VB3,VB416-or32-bit,VB5,orVB6.Pleaselimitcodelengthto20lines.Don,tforgettoincludeyoure-mailandmailingaddress.Ifwepublishyourtip,we,llpayyou$25orextendyourVBPJsubscriptionbyoneyear.VB

4、5,VB61.evel:BeginningPreventCheckboxChangesYou,11oftenwanttodisplayacheckbox-stylelistboxtoshowusersthevaluestheyhaveselectedinanunderlyingdatabase.However,youdon,twanttoallowuserstochangetheselections-thatis,tochangewhichboxestheychecked.Youcan,tdisablethelistboxbecausethatstopstheuserfromscrolling

5、thelisttoseewhichitemstheychecked.Youcan,tuse1.ocked,becausethelistboxdoesn,thavea1.ockedproperty.Here,sonesolution:PaintaCommandbuttonwiththecaptionttClicktotoggleenabledproperty,andalistboxonaform,thenchangethelistboxstyleto1-Checkbox.Addthiscode:OptionExplicitDimmbDisabledAsBooleanPrivateSubComma

6、ndl_Click()mbDisabled=NotmbDisabledEndSubPrivateSub1.istl_ltemCheck(ltemAsInteger)IfmbDisabIedThen1.istl-SeIected(Item)=Not1.istl.SeIected(Item)EndIfEndSubWhenmbDisabledissettoTrue,thechangesmadebytheusertothelistboxselectionsareimmediatelyreversed.Itwillappearasiftheselectionshaven,tchangedatall,an

7、dthelistisstillscrollable.IanChamp,receivedbye-mail牟*余字*余*拿木*今*车窄*专*车*车*车窄*余*余*车本*余申*余*拿*拿*余*东*卒*车*余*京字*车*车*余辛*率*多*拿*VB432,VB5,VB61.evel:IntermediateEstablishaDataDictionaryIfyourSQ1.lookslikethis,youneedtoaskyourselfhowmuchcodeyou,dhavetoinspectandreviseifyoudecidedtochangeadatabasefieldortablename

8、,asfrequentlyhappensduringdevelopment:SQ1.String=SE1.ECTfirstname,lastname,&_linepreferences&_FROMimagingusersWHEREusercode=_,&Trim(UCase(UserlDText.Text)&,11ODBCstatus=SQ1.ExecDirect(ODBChandlel,SQ1.String,_1.en(SQ1.String)WhathappensifSQmandconventions(fieldnamedelimiters)change?Becauseacompiledoe

9、sn,trevealsuchnamemisspellingsorconventionflaws,codeinobscureprocedurescanbeinproductionbeforedefectsaredetected.Ourgroupestablishedatableandfielddictionaryinamoduleusedforarecentlargeproject.ThishelpedusensurethatwecorrectlypastedtableandfieldnamesintoallSQmands.Italsoprovidedarepositorythatsimplif

10、iedmaintenance.Asdatabaseresourcenameschangedornewname-delimitingconventionswererequired,werevisedthedictionarybeforerecompiling.Wealsousedthedictionarytoconveydescriptiveinformationabouttablesandfieldstodevelopers.Ourdictionarylookslikethis:tables:PublicConsttblUsersAsString=(imagingusersdatafields

11、:PublicConstfldFirstNameAsString=(firstname16charactersPublicConstfld1.astNameAsString=(lastname16charactersPublicConst(Id1.inePreferencesAsString=_linepreferences20charactersPublicConstfldUserCodeAsString=usercodeIOcharactersOurSQ1.lookslikethis:SQ1.String=SE1.ECT&fldFirstName&_,&fld1.astName&_,&fl

12、d1.inePreferences&_FROM,&tblUsers&_,WHERE&fldUserCode&=&_&Trim(UCase(UserlDTet.Text)&,ODBCstatus=SQ1.ExecDirect(ODBChandlel,SQ1.String,_1.en(SQ1.String)Programmersdonthavetoknowtheactualnamesofdatabasecomponents.Theyalwaysusetheconstantsthatrefertothedatabasecomponents.Acleancompileensuresyou,11usec

13、orrectnamesandname-delimitingconventionsinyourSQ1.statements.DougIIagy,Greensburg,Pennsylvania余*牟申*率*率*牟*辛*牟*拿*本*车申*率*牟*车*拿*拿*率*多*余*牟*牟*辛*专*牟*柴*VB432,VB5,VB61.evel:IntermediateContext-SensitiveHelpforDisabledControlsIfyouwantaformtosupportcontext-sensitivehelp,settheWhatsThisButtonandWhatsThisHeIppr

14、opertiesontheformtoTrue,andsettheWhatsThisHelpIDpropertytoacorrespondinghelp-filetopicIDforanycontrolonthatformforwhichyouwanthelptobedisplayed.Unfortunately,thehelpisn,tshownifthecontrosEnabledpropertyissettoFalse.Tosolvethisproblem,createalabelunderthecontrolwiththesamedimensions,andclearitscaptio

15、ntomakeitinvisible.SettheWhatsThisHelpIDpropertytothesamevalueasthedisabledcontrosproperty.FrankAddati9Melbourne,Australia车*余*辛*车申*车*多*拿车*拿*拿*木*余辛*车*辛*车*车本*余*拿辛*专车*率*余?*拿*车*专*车本*车*拿*拿?*辛*拿*多*车*余本*VB3,VB416/32,VB5,VB61.evel:IntennediateImproveontheBubbleSortAbubblesort,sexecutiontimeisamultipleofthesquareofthenumberofelements.Becauseofthis,thebubblesort