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how to parse an Enum Structure in vb.netPublic Enum MyEnum EnumVal1=0 EnumVal2=1 EnumVal2=2 end enum I save in an access database this enum value as an integer (0=EnumVal1, 1=EnumVal2, 2=EnumVal) When retreving this enum from the database how do I ensure that the correct value is passed to my object For instance MyObject.MyEnum=1 . Does this populate the property with MyObject.MyEnum= EnumVal2 giannik "giannik" <giannik@newsgroups.nospam> schrieb: \\\>I have an Enum Structure > > Public Enum MyEnum > EnumVal1=0 > EnumVal2=1 > EnumVal2=2 > > end enum > > I save in an access database this enum value as an integer (0=EnumVal1, > 1=EnumVal2, 2=EnumVal) Dim e As MyEnum = CType(v, MyEnum) /// -- M S Herfried K. Wagner M V P <URL:http://dotnet.mvps.org/> V B <URL:http://classicvb.org/petition/> You have nothing special to do. See EnumVal2 has being just a symbolic name
for the value 1 (similarly to a constant). So if MyObject.MyEnum=1, MyObject.MyEnum=MyEnum.EnumVal2 because MyEnum.EnumVal2 is also 1. -- Patrice "giannik" <giannik@newsgroups.nospam> a écrit dans le message de news: %23WnH1%23CoGHA.4***@TK2MSFTNGP05.phx.gbl...Show quoteHide quote >I have an Enum Structure > > Public Enum MyEnum > EnumVal1=0 > EnumVal2=1 > EnumVal2=2 > > end enum > > I save in an access database this enum value as an integer (0=EnumVal1, > 1=EnumVal2, 2=EnumVal) > > > When retreving this enum from the database how do I ensure that the > correct value is passed to my object > > For instance > > > MyObject.MyEnum=1 . > Does this populate the property with MyObject.MyEnum= EnumVal2 > giannik > ok. Thank you very much
Show quoteHide quote "Patrice" <scr***@chez.com> wrote in message news:e8NireDoGHA.4648@TK2MSFTNGP05.phx.gbl... > You have nothing special to do. See EnumVal2 has being just a symbolic > name for the value 1 (similarly to a constant). > > So if MyObject.MyEnum=1, MyObject.MyEnum=MyEnum.EnumVal2 because > MyEnum.EnumVal2 is also 1. > > -- > Patrice > > "giannik" <giannik@newsgroups.nospam> a écrit dans le message de news: > %23WnH1%23CoGHA.4***@TK2MSFTNGP05.phx.gbl... >>I have an Enum Structure >> >> Public Enum MyEnum >> EnumVal1=0 >> EnumVal2=1 >> EnumVal2=2 >> >> end enum >> >> I save in an access database this enum value as an integer (0=EnumVal1, >> 1=EnumVal2, 2=EnumVal) >> >> >> When retreving this enum from the database how do I ensure that the >> correct value is passed to my object >> >> For instance >> >> >> MyObject.MyEnum=1 . >> Does this populate the property with MyObject.MyEnum= EnumVal2 >> giannik >> > > giannik wrote:
> I have an Enum Save the Enum /names/ not their numeric values.> > Public Enum MyEnum > EnumVal1=0 > EnumVal2=1 > EnumVal2=2 > end enum > > I save in an access database this enum value as an integer (0=EnumVal1, > 1=EnumVal2, 2=EnumVal) OK, you only have three here, but what if you had a long list of these and then, Lord forbid, you added another one "in the middle"? Much of your existing data (in Access) would be wrong. Use a String column in the database and use <value>.ToString() to get the enum "name" to save. > When retreving this enum from the database how do I ensure that the correct When reading the property back, parse the string value (from Access) > value is passed to my object back into the Enum Type, as in MyObject.MyEnum = CType( dr.Item( "EV" ), MyEnum ) By way of a rather silly example: Class MyClass Enum Month January = 1 February March . . . dr.Item( "Month" ) = Month.December.ToString() ' actually "December" Now, just for the sake of argument, let's create a new month, called Filibuster, between February and March. Class MyClass Enum Month January = 1 February Filibuster March . . . Oh No! I hear you cry. You'll have to bulk update all the records in Access to increment their month numbers! Nope. Holding the Enum /names/ means you don't have to. Assuming you already have a row in there for December: ? dr.Item( "Month" ).GetType().ToString() [System.]String ? dr.Item( "Month" ).ToString() "December" ? CType( dr.Item( "Month" ), Month ).GetType().ToString() [MyClass.]Month ? CType( dr.Item( "Month" ), Month ) December So far, so good, but here's the clincher ... ? CInt( dr.Item( "Month" ), Month ) 13 .... even if it was 12 when you saved that record into Access! HTH, Phill W. It seems a waste to use strings as opposed to integers in a database for
ENUMS. You can just as easily assign numbers to each enum value, i.e., Enum Month January = 10 February = 20 March = 30 . . . In the new enum; Enum Month January = 10 February =20 Filibuster = 25 March =30 . . . -- Show quoteHide quoteDennis in Houston "Phill W." wrote: > giannik wrote: > > I have an Enum > > > > Public Enum MyEnum > > EnumVal1=0 > > EnumVal2=1 > > EnumVal2=2 > > end enum > > > > I save in an access database this enum value as an integer (0=EnumVal1, > > 1=EnumVal2, 2=EnumVal) > > Save the Enum /names/ not their numeric values. > OK, you only have three here, but what if you had a long list of these > and then, Lord forbid, you added another one "in the middle"? Much of > your existing data (in Access) would be wrong. > > Use a String column in the database and use <value>.ToString() to get > the enum "name" to save. > > > When retreving this enum from the database how do I ensure that the correct > > value is passed to my object > > When reading the property back, parse the string value (from Access) > back into the Enum Type, as in > > MyObject.MyEnum = CType( dr.Item( "EV" ), MyEnum ) > > By way of a rather silly example: > > Class MyClass > Enum Month > January = 1 > February > March > . . . > > dr.Item( "Month" ) = Month.December.ToString() ' actually "December" > > Now, just for the sake of argument, let's create a new month, called > Filibuster, between February and March. > > Class MyClass > Enum Month > January = 1 > February > Filibuster > March > . . . > > Oh No! I hear you cry. You'll have to bulk update all the records in > Access to increment their month numbers! > Nope. Holding the Enum /names/ means you don't have to. Assuming you > already have a row in there for December: > > ? dr.Item( "Month" ).GetType().ToString() > [System.]String > ? dr.Item( "Month" ).ToString() > "December" > ? CType( dr.Item( "Month" ), Month ).GetType().ToString() > [MyClass.]Month > ? CType( dr.Item( "Month" ), Month ) > December > > So far, so good, but here's the clincher ... > > ? CInt( dr.Item( "Month" ), Month ) > 13 > > .... even if it was 12 when you saved that record into Access! > > HTH, > Phill W. > Storing the integer value rather than the name does perform better.
Storing the names is something that should be considered in some cases, though. In some cases the names correspond naturally to a number that won't change, for an example the months that are numbered from 1 through 12. Then there is no reason to store the name instead of the number. In other cases the names have no natural numbering at all, then it might be better to store the names. The numbers are only used internally by the application, and the data in the database is meningful without a translation table. Dennis wrote: Show quoteHide quote > It seems a waste to use strings as opposed to integers in a database for > ENUMS. You can just as easily assign numbers to each enum value, i.e., > > Enum Month > January = 10 > February = 20 > March = 30 > . . . > > In the new enum; > Enum Month > January = 10 > February =20 > Filibuster = 25 > March =30 > . . . > 
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