《VB2008从入门到精通(PDF格式英文版)》第159章

definitions。dll　reside　in　the　current　directory）。
gacutil　/I　definitions。dll　
gacutil　/I　implementations2。dll　
Remember　to　add　Definitions；　because　Implementations2　depends　on　Definitions。
Failing　to　add　Definitions　will　generate　gacutil　errors。　
ORGANIZING　DYNAMIC　CODE　
If　you　are　going　to　place　files　in　the　GAC；　don’t　use　the　techniques　demonstrated　in　this　book　when　doing　a
production　release。　The　techniques　discussed　in　this　book　are　meant　for　developers；　and　only　developers。　The
techniques　are　shortcuts　that　assume　you　know　what　the　dependencies　are　and　are　aware　of　what　you　are
doing。　For　distribution　purposes；　use　the　Microsoft　Windows　Installer　application　to　install　files　into　the　GAC。　
When　writing　dynamic　code；　the　idea　is　to　separate　and　pletely　partmentalize　the　development
of　the　ponent　and　the　caller　of　the　ponent。　Thus；　you　should　not　develop　both　pieces　in　the　same
project。　Create　separate　projects　and　have　them　working　with　test　routines。　Then；　at　runtime；　bine　the
functionalities；　and　everything　should　work　（that　is；　if　you　properly　tested　your　code）。　
Using　Version　Numbers　
Version　numbers　are　a　way　of　being　able　to　control　the　features　and　robustness　of　an　applica
tion。　In　the　packaged　software　market；　the　concept　of　the　version　number　has　nearly　disappeared。
For　example；　consider　Microsoft’s　operating　system　versions：　Windows　95；　Window　98；
Windows　XP；　Windows　2000；　Windows　Vista；　and　so　on。　
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334 CH　AP　T　E　R 1　2 ■ L　E　A　R　N　I　N　G A　B　OU　T A　PP　L　I　CA　TI　O　N CO　N　F　I　G　U　R　AT　IO　N AN　D D　Y　N　A　M　I　C L　O　AD　I　N　G　
In　open　source　software；　version　numbers　are　used　extensively　and　are　considered　very
important。　Yes；　the　version　numbers　resemble　a　lottery　ticket；　but　they　do　follow　a　convention。
Understanding　the　convention　makes　it　easier　to　select　open　source　packages。　And　more
important；　applying　this　versioning　strategy　makes　it　simpler　to　understand　your　assemblies。　
Understanding　Version　Numbers　
Let’s　say　you　want　to　download　the　open　source　program　Capivara　（a　Java　file　manager　and
synchronization　program）。　You　see　the　version　number　0。8。3。　The　version　number　contains
three　parts：　
Major　number：　The　major　number　is　0　in　the　example。　If　the　software　has　not　reached　the
number　1；　the　version　is　considered　a　beta。　But　often；　a　beta　identifier　does　not　mean
the　version　is　unusable。　Changing　the　major　version　number　indicates　a　major　change
of　functionality。　This　means　what　worked　in　version　1　may　not　work　with　version　2。　An
example　is　the　Apache　HTTPD　server　project；　where　the　1。x　and　2。x　series　are　two　different
implementations。　
Minor　number：　The　minor　number　is　8　in　the　example。　It　is　used　to　define　minor　function
ality　changes　in　a　piece　of　software。　Changing　the　minor　number　（such　as　7　to　8）　indicates
new　features；　but　old　functionality　is　supported。　A　change　may　include　bug　fixes　or　patches。　
Patch　number：　The　path　number　is　3　in　the　example。　It　is　used　to　define　a　patched　version
of　the　software　that　has　bug　fixes　or　other　changes。　The　changes　do　not　include　features；
and　the　functionality　does　not　change。　
When　you　attempt　to　download　an　open　source　package；　you　are　typically　confronted　with
multiple　versions。　For　example；　you　might　see　the　version　numbers　4。23　and　4。29　（beta）。　Because
most　people　want　the　latest　and　greatest；　they　might　be　tempted　to　download　4。29。　But　remember
that　open　source　projects　make　multiple　versions　available。　In　the　example；　you　should　down
load　version　4。23；　because　4。29　is　a　beta　that　may　or　may　not　work。　Version　4。23　is　considered
stable　and　therefore　usable。　
The　open　source　munity　will　often　use　the　following　terminology　when　releasing
software。　
o Stable：　A　version　that　can　be　used　in　a　production　environment　and　should　not　crash。　
o Unstable：　A　version　that　should　not　be　used　in　production。　It　will　probably　work；　but
have　some　crashes。　
o Nightly：　A　version　with　all　bets　off；　meaning　that　the　version　may　or　may　not　work。　The
reason　for　using　a　nightly　build　is　to　monitor　progress　and　check　specific　issues。　Such　a
version　is　not　intended　for　consumer　consumption；　it　is　intended　solely　for　developers。　
o Alpha　：　A　version　that　demonstrates　the　concepts　that　will　make　up　a　future　version　of　the
software。　However；　in　alpha　versions；　what　was　available　one　day　might　be　gone　the
next　day。　
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CH　AP　T　E　R 1　2 ■ L　E　AR　N　IN　G AB　O　U　T AP　P　L　I　CAT　I　ON CO　N　F　IG　U　R　AT　IO　N A　N　D D　Y　N　A　M　IC L　O　AD　IN　G　335　
Versioning　Assemblies　
assembly　version　numbers　are　different　from　those　used　for　open　source　packages。　The
following　is　an　example　of　versioning　an　assembly。　
The　attributes　AssemblyVersion　and　AssemblyFileVersion　can　be　added　anywhere　in　the
assembly　or　application。　In　Visual　Basic　Express；　most　likely　the　attributes　are　added　to　the　file
AssemblyInfo。vb。　
The　versions　of　the　file　have　four　significant　parts。　From　left　to　right；　these　are　major
version；　minor　version；　build　number；　and　revision。　The　build　number　can　represent　a　daily
build　nu