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1、IntroductionIhaveseenquitealotofcodeexplaininghowtouseclassesexportedfromaDLLinanapplication.However,allthesedescribetheusageoftheexportedclassesbylinkingimplicitlytotheDLL.RefreshingourDLLconcepts,therearetwowaysforanapplicationtouseafunctionwritteninaDLL.Thefirstwayistohaveyourapplication'ssour
2、cecodesimplyreferencesymbolscontainedintheDLL.Thiscausestheloadertoimplicitlyload(andlink)therequiredDLLwhentheapplicationisinvoked.Thisisknownasimplicitlinking.ThesecondwayisfortheapplicationtoexplicitlyloadtherequiredDLL(usingaLoadLibrary()call)andexplicitlylinktothedesiredexportedsymbolwhileth
3、eapplicationisrunning.Inotherwords,iftheapplicationdecidesthatitwantstocallafunctioninaDLL,itcanexplicitlyloadtheDLLintotheprocess'addressspace,getthevirtualmemoryaddressofthefunctioncontainedwithintheDLL,andthencallthefunctionusingthismemoryaddress.Thebeautyofthistechniqueisthateverythingisdonew
4、hiletheapplicationisrunningandtheapplicationcanunloadtheDLLfromitsprocessaddressspacewhenithasfinisheditsworkwiththeDLL.Asyoumighthaveguessed,thistechniqueisknownasexplicitlinking.BackgroundSofar,Ispokeofusingfunctions,buthey,whataboutusingclassesexportedfromaDLL?Well,inthecaseofimplicitlylinkedD
5、LLs,thereisnodifferenceatall.ButwhataboutloadingDLLsexplicitlyandusingtheexportedclasses?Well,undernormalcircumstances,itcannotbedone,butIwrotethisarticlenottoexplaintoyouwhyitcannotbedone,buttogiveyouanideaastohowyoucandoit.That'sright!!UsingexportedclassesbyloadingaDLLusingaLoadLibrary()call.Bu
6、tbeforeproceedingfurther,Iwarnyouthatthemethodgivenbelowissortofahack,andifforanyreasonyouplantouseitinyourproject,pleasetakethepriorapprovalofyourboss...(ifbyanychanceyoudomanagetogethis/herapprovalonthistechnique!!).However,thiscolumnisbasicallyforyourunderstandingandalsoforextremecaseswhenyouj
7、ustcantdowithoutthishack.UsingthecodeIfyoulookatthesamplecode,youcanseethatIhavecreatedaCalculatorDLLcalledCalc.DLLandIamusingthecalculatingpowerspresentintheDLLinmyconsoleapplicationcalledUserOfCalc(Icouldn'tthinkofab
