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

WelcometotheEighthEditionoftheVBPJTechnicalTipsSupplement!ThesetipsandtricksweresubmittedbyprofessionaldevelopersusingVisualBasic3.0,VisualBasic4.0,VisualBasic5.0,VisualBasic6.0,VisualBasicforApplications(VBA),andVisualBasicScript(VBS).TheeditorsatVisualBasicProgrammer,sJournalcompiledthetips.Insteadoftypingthecodepublishedhere,downloadthetipsfromthefree,Registered1.evelofTheDevelopmentExchangeat.Ifyou,dliketosubmitatiptoVisualBasicProgrammer,sJournal,pleasesendittoUserTips,FawcetteTechnicalPublications,209HamiltonAve.,PaloAlto,California,USA,94301-2500.Youcanalsofaxitto650-853-0230orsenditelectronicallytovbpjedit.Pleaseincludeaclearexplanationofwhatthetechniquedoesandwhyit,suseful,andindicateifit,sforVBA,VBS,VB3,VB416-or32-bit,VB5,orVB6.Pleaselimitcodelengthto20lines.Don,tforgettoincludeyoure-mailandmailingaddress.Ifwepublishyourtip,we,llpayyou$25orextendyourVBPJsubscriptionbyoneyear.VB5,VB61.evel:BeginningPreventCheckboxChangesYou,11oftenwanttodisplayacheckbox-stylelistboxtoshowusersthevaluestheyhaveselectedinanunderlyingdatabase.However,youdon,twanttoallowuserstochangetheselections-thatis,tochangewhichboxestheychecked.Youcan,tdisablethelistboxbecausethatstopstheuserfromscrollingthelisttoseewhichitemstheychecked.Youcan,tuse1.ocked,becausethelistboxdoesn,thavea1.ockedproperty.Here,sonesolution:PaintaCommandbuttonwiththecaptionttClicktotoggleenabledproperty,'andalistboxonaform,thenchangethelistboxstyleto1-Checkbox.Addthiscode:OptionExplicitDimmbDisabledAsBooleanPrivateSubCommandl_Click()mbDisabled=NotmbDisabledEndSubPrivateSub1.istl_ltemCheck(ltemAsInteger)IfmbDisabIedThen1.istl-SeIected(Item)=Not1.istl.SeIected(Item)EndIfEndSubWhenmbDisabledissettoTrue,thechangesmadebytheusertothelistboxselectionsareimmediatelyreversed.Itwillappearasiftheselectionshaven,tchangedatall,andthelistisstillscrollable.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,asfrequentlyhappensduringdevelopment:SQ1.String="SE1.ECTfirstname,lastname,"&_"linepreferences"&_"FROMimagingusersWHEREusercode="_","&Trim(UCase(UserlDText.Text)&,11"ODBCstatus=SQ1.ExecDirect(ODBChandlel,SQ1.String,_1.en(SQ1.String)WhathappensifSQmandconventions(fieldnamedelimiters)change?Becauseacompiledoesn,trevealsuchnamemisspellingsorconventionflaws,codeinobscureprocedurescanbeinproductionbeforedefectsaredetected.Ourgroupestablishedatableandfielddictionaryinamoduleusedforarecentlargeproject.ThishelpedusensurethatwecorrectlypastedtableandfieldnamesintoallSQmands.Italsoprovidedarepositorythatsimplifiedmaintenance.Asdatabaseresourcenameschangedornewname-delimitingconventionswererequired,werevisedthedictionarybeforerecompiling.Wealsousedthedictionarytoconveydescriptiveinformationabouttablesandfieldstodevelopers.Ourdictionarylookslikethis:'tables:PublicConsttblUsersAsString="(imagingusers"'datafields:PublicConstfldFirstNameAsString="(firstname"'16charactersPublicConstfld1.astNameAsString="(lastname"'16charactersPublicConst(Id1.inePreferencesAsString=_"linepreferences"'20charactersPublicConstfldUserCodeAsString="usercode"'IOcharactersOurSQ1.lookslikethis:SQ1.String="SE1.ECT"&fldFirstName&_",&fld1.astName&_","&fld1.inePreferences&_"FROM,&tblUsers&_,WHERE"&fldUserCode&"="&_"'"&Trim(UCase(UserlDTe×t.Text)&","ODBCstatus=SQ1.ExecDirect(ODBChandlel,SQ1.String,_1.en(SQ1.String)Programmersdon'thavetoknowtheactualnamesofdatabasecomponents.Theyalwaysusetheconstantsthatrefertothedatabasecomponents.Acleancompileensuresyou,11usecorrectnamesandname-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,settheWhatsThisButtonandWhatsThisHeIppropertiesontheformtoTrue,andsettheWhatsThisHelpIDpropertytoacorrespondinghelp-filetopicIDforanycontrolonthatformforwhichyouwanthelptobedisplayed.Unfortunately,thehelpisn,tshownifthecontrosEnabledpropertyissettoFalse.Tosolvethisproblem,createalabelunderthecontrolwiththesamedimensions,andclearitscaptiontomakeitinvisible.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