tips_7 面向VisualBasic程序员的杂志 第7版.docx

WelcometotheSeventhEditionoftheVBPJTechnicalTipsSupplement!VB3,VB416/32,VB51.evel:BeginningDeletinganArrayElementConventionalwisdomsuggeststhattodeleteanarrayelement,youmustmoveupallthesubsequentelementstoclosethegap"leftbythedeleteditem.However,ifthesequenceoftheelementsisn'tsignificant(asinanunsortedarray),thisalgorithmquicklydeletesanitem:,Elementtodelete(Delete=5'NumberofelementsbeforedeletionnElements三UBound(Array)'ReplaceiDeletewithlastiteminarrayArray(IDeIete)=Array(nElements)*UseReDimPreservetoshrinkarraybyoneReDimPreserveArray(1.Bound(Array)_TonElements-1)一BasilHubbard,Hammon,Omario,CanadaVB432,VB5,VBA1.evel:IntermediateInvokehOpenWith.,DialogBoxWhenlaunchingadatafilewiththeSheIIExecuteOfunction,Windowstriestofindtheassociatedapplicationandopenthedatafilewiththisapplication.Butwhathappensifnoassociationexists?SheIIExecuteOsimplyreturnserrorde31(noassociation)andnothinghappens.Wouldn'titbeniceifyourprograminvokedthe41Openwith."dialogboxsoyoucanchsewhichapplicationyouwanttoassociatewithyourdatafile?Here'sasolution-calltheSheIIDocroutineandpassafullyqualifiedpath/filenameofthedatafileyouwishtoopen:OptionExplicitDeclareFunctionGetDesktopWindow1.ib,tuser32,()As1.ongDeclareFunctionSheIIExecute1.ib_,shell32.drAlias"SheIIExecuteA'.(ByVaIhW11dAs1.ong,ByVaIIpOperation_AsString,ByVaIIpFiIeAsString,_ByVaIIpParametersAsString,_ByVaIIpDirectoryAsString,_ByVaInShowCmdAs1.ong)As1.ongDeclareFunctionGetSystemDIrectoryUb_“kemel32"Alias"GetSystemDirectoryA"_(ByVaIIpBufferAsString,ByVaInSize_As1.ong)As1.ongPrivateConstSE-ERR-NOASSOC=31PublicSubShellDoc(strFileAsString)DimIngRetAs1.ongDimStrDirAsStringIngRet=SheHEXeCUte(GetDeSktoPWindOw,_"open”,StrFiIe,_VbNuIIString1VbNuIIString.VbNormaIFocus)IfIngRet=SE_ERR_NOASSOCThen'noassociationexistsStrDir三Space(260)IngRet=GetSyStemDireCtOry(StrDir,_1.en(StrDIr)StrDir三1.eft(strDir,IngRet)'showtheOpenwithdialogboxCallShellExecutefGetDesktopWindow,_VbNuIIString,RUND1.1.32.EXE-,Mshell32.dll,OpenAs.RunD1.1.”&_StrFite1StrDir1VbNormaIFocus)EndIfEndSub-ThomaSWeidmannjeceivedbyemailVB432,VB51.evel:BeginningSSTABVs.OptionButtonsAlthoughVB,sSSTabntrolbehavesasifeachtabpageisacontainer,itactuallyusesasinglecontainerforalltabpages.Thiscancauseunexpectedbehaviorifyouhavegroupsofoptionbuttonsondifferentpages.Clickingonanoptionbuttonononepageclearsalltheuncontainedoptionbuttonsontheother,seeminglyunrelated,pages.Solvethisproblembyaddingyourowncontainersframesorpictureboxes)foreachgroupofoptionsyouwanttobemutuallyexclusive.SteveCiSCoandROIandSOUtharaFranklin,TenneSSeeVB432,VB51.evel:BeginningChangetheAppearancePropertyofaTextBoxatRunTimeSorry,youcan'tchangetheAppearancepropertyofatextboxatruntimebutyoucanmakeitlooklikeyouhave!Ifsettonone,a3-DpictureboxhasaflatBorderStyIeproperty.Putyourtextbox(withaflatappearance)insideapicturebox(witha3-Dappearance)andchangethepicturebox'sborderstyle.UsethiscompletecodebesureyouplaceText1insidePicturel:Privatem_TextVAppearanceAs1.ongPrivateSubForm_1.oad()WithText1Picturel.Width=.WidthPicturel-Height三.Height.MoveO,OEndWithText1_Appearance1,3DEndSubPublicProperty1.et_Text1_Appearance(nAppearanceAs1.ong)WithPicturelSelectCasenAppearanceCaseO'Flat.BorderStyIe三nAppearanceCase1,3D.BorderStyIe=nAppearanceEndSelectm_Text1_Appearance三.BorderStyIeEndWitfCEndPropertyPublicPropertyGetText1_AppearanceOAs1.ongTeXt1.APPearanCe三m_Text1_AppearanceEndPropertyJimDeutch,CaZenOvia,NeWYorkVB432,VB51.evel:BeginningDealingWithNullValuesReturnedFromRDOResultsetsIfyou,rassigningthevaluesoflumnsyoureturnfromRDOqueriesintostringvariables,you,llgetan"InvaliduseofNulerrorifoneofthecolumnshasaNullvalue.Formostpurposes,dratherhavethevalueasanemptystringanyway.RatherthancodeforthateachtimeIaccessacolumn,l,vewrittenafunctioncalledCleanthatturnsNullvaluesintoemptystrings.Icallitlikethis:strMyString=Clean(rdoResultset(MMyVarCharColumnM)IalsoconvertEmptyvaluesaswell,forusewithVariants:PublicFunctionClean(ByValvarDataAsVariant)AsStringIfIsNuII(VarData)ThenClean三"ElselfIsEmpty(VarData)ThenClean=ElseClean=CStr(VarData)EndlfEndFunction-JameST.Stanley,MuncieJndianaVB3,VB416/32,VB51.evel:BeginningInSearchofSampleCodemalwayslookingforsamplecode,andthesetup1.vbpfileisanexcellentsourceofreusablecode.ItcomeswithVBandispartoftheVBsetupkit.Thecontentsvary,dependingonwhatversionofVByouhave,butyou'llfindusefulexamplesineachversion.Forexample,theVB5filesamplecodedoesthesethings: GetstheWindowsdirectory. GetstheWindowsSystemdirectory. Determinesifafileordirectoryexists. Determinesifyou'rerunningWinNTorWin95.,Determinesdrivetype. Checksdiskspace. Createsanewpath. ReadsfromanINIfile. Parsesdateandtime. Retrievestheshortpathnameofafilentaininglongfilenames.Plus,awholemoduleworkstologerrorstoanerrorfile.Thisdeiswell-commentedandcaneasilybecutandpastedintoyourproject.