You can simplify it and just do:
IList<Gender> genders = session.CreateQuery("from Gender").List<Gender>();
Sean
On Mon, Feb 9, 2009 at 10:18 PM, Dathan <[email protected]> wrote:
>
> Okay, so I'll look at pursuing that route for Gender. Then what's the
> best way to get a list of valid Gender's for displaying in the UI?
> Something like (haven't tested this, just pulled it from the reference
> docs -- the Cat example):
>
> List<Gender> genders = new List<Gender>();
> IQuery query = session.CreateQuery("select c from Gender as c");
> foreach (Gender g in query.Enumerable())
> {
> genders.Add(g);
> }
>
> Am I on the right track?
>
> On Feb 9, 7:49 pm, Jason Meckley <[email protected]> wrote:
>> the list of genders (or whatever look up) should be separate from the
>> actual entity. validation can be done any number of ways. attributes,
>> Validator<T>, or a series of simple bool returning members on the
>> entity itself. I would treat Gender as a value object/entity using NH
>> mappings instead of a string. this would allow for strategies of
>> gender specific functionality. instead of logic like
>>
>> if(person.gender == "M"
>> {}
>>
>> else if(person.gender == "F")
>> {
>>
>> }
>>
>> you could do
>> person.gender.dosomething();
>>
>> i would probably go with a combination of validation attributes
>> (castle validation component) and IValidator<T> where the validation
>> logic can be placed in a central location. The systems I design are
>> small so I find this works well for me.
>>
>> On Feb 9, 7:04 pm, Dathan <[email protected]> wrote:
>>
>> > Something like
>> > PersonTbl (PersonId INTEGER PRIMARY KEY IDENTITY(1,1), Name NVARCHAR
>> > (255), GenderId INTEGER REFERENCES GenderTbl(GenderId));
>> > GenderTbl (GenderId INTEGER PRIMARY KEY IDENTITY(1,1), Gender NVARCHAR
>> > (10));
>>
>> > But where Person.Gender is a string, and is at some point by the DAL
>> > resolved into the GenderId that corresponds to the value of the Gender
>> > column with the same string value.
>>
>> > The contents of GenderTbl should never be changed by the DAL (I don't
>> > want users defining new genders!), but we do have a case where users
>> > being able to add to such a list might be necessary (e.g., it might be
>> > necessary to allow users to add new cities to our gazeteer). So,
>> > since I'm a newbie to the terminology, yes, you might say the Gender
>> > list is persistent, but I'm not trying to persist a collection of
>> > genders per person. Just a single Gender per person, plus supporting
>> > some mechanism for validating that what the user has selected in the
>> > frontend is a valid gender.
>>
>> > But I guess even that's not quite right... I don't want to persist a
>> > Gender object per Person (a one-to-one relationship). I want to
>> > create a many-to-one relationship where each Person has a reference to
>> > either the, e.g., "Male", "Female", or "Unknown" gender. But I'd like
>> > to be able to, somewhere (and it just makes sense to me to do it as
>> > part of the object model, rather than externally in the UI logic), get
>> > a list of all valid genders (currently I do this as a string -- would
>> > it make more sense to create a Gender object for this?) for use both
>> > in validating user input (is the user's input in the set of valid
>> > genders?), and in UI presentation.
>>
>> > On Feb 9, 4:39 pm, Fabio Maulo <[email protected]> wrote:
>>
>> > > The "Gender" list is persistent ?
>>
>> > > 2009/2/9 Dathan <[email protected]>
>>
>> > > > Thanks for the reply!
>>
>> > > > The list is, as you surmise, for UI drop-down population, but also for
>> > > > run-time validation. I'd rather validate the value of the Gender
>> > > > property immediately (via either Dictionary.ContainsKey() or List.Find
>> > > > (), as you suggest) than waiting for NHibernate to throw an error when
>> > > > I try to serialize the entity back to the data store (I'm an NH
>> > > > newbie, so please correct me if I'm wrong about the behavior in this
>> > > > regard). I'm open to advice on best practices, though, if this is the
>> > > > wrong way to go about it.
>>
>> > > > Given that a list of valid genders is also of use in data validation
>> > > > (which seems to be very much a domain concern, rather than strictly a
>> > > > UI concern), not just UI control, it seems logical to me that embedded
>> > > > in the person entity is an appropriate place for this information. I
>> > > > take it this is contrary to DDD / MVC / other best practices?
>>
>> > > > ~Dathan
>>
>> > > > On Feb 9, 3:33 pm, Jason Meckley <[email protected]> wrote:
>> > > > > why does the person entity have a static list of genders? if it's
>> > > > > just
>> > > > > for UI dropdown list selection, this can, and should, be done outside
>> > > > > to scope of the person entity.
>> > > > > I would also recommend using 2nd level cache for memory storage of
>> > > > > the
>> > > > > gender list rather than a static list. and I would recommend waiting
>> > > > > on implementing the cache until
>> > > > > 1. preformance is a documented and measurable issue
>> > > > > 2. the problem is loading the genders and not another issue (select n
>> > > > > +1 or unrestricted list results).
>>
>> > > > > the person entity would just have a Gender property which you would
>> > > > > get;set; to a Gender field. no need for a dictionary of genders
>> > > > > within
>> > > > > the person entity. also, if you are going to keep a collection on any
>> > > > > entity. use IList<T>, in this case IList<Gender>. key, value
>> > > > > containers do not express intent and the same functionality can be
>> > > > > gained using list.Find(predicate).
>>
>> > > > > On Feb 9, 12:45 pm, Dathan <[email protected]> wrote:
>>
>> > > > > > I'm considering porting my existing DAL to NHibernate instead. But
>> > > > > > I've been reading the documentation, and there's one feature of the
>> > > > > > way my object model currently works that I haven't figured out an
>> > > > > > elegant way to do using NHibernate yet.
>>
>> > > > > > Say I'm representing a person. That person has a Gender property.
>> > > > > > In
>> > > > > > the database, that gender property is a foreign key to
>> > > > > > GenderTbl.GenderId, and GenderTbl.Gender holds the string that
>> > > > > > describes the person's gender. What I'm doing currently is having
>> > > > > > something like the following:
>>
>> > > > > > public class Person
>> > > > > > {
>> > > > > > private string gender;
>> > > > > > private static Dictionary<string, int> genderDict;
>> > > > > > private static IList<string> genderList;
>> > > > > > .
>> > > > > > .
>> > > > > > .
>> > > > > > public string Gender
>> > > > > > {
>> > > > > > get
>> > > > > > {
>> > > > > > return gender;
>> > > > > > }
>> > > > > > set
>> > > > > > {
>> > > > > > if (!genderDict.ContainsKey(value))
>> > > > > > throw new ArgumentException("Invalid gender");
>> > > > > > gender = value;
>> > > > > > }
>> > > > > > }
>>
>> > > > > > public IList<string> GenderList
>> > > > > > {
>> > > > > > get
>> > > > > > {
>> > > > > > return genderList;
>> > > > > > }
>> > > > > > }
>>
>> > > > > > }
>>
>> > > > > > My DAL initializes Person.genderDict and Person.genderList to
>> > > > > > reflect
>> > > > > > the contents of GenderTbl -- genderDict is used to lookup the
>> > > > > > primary
>> > > > > > key of a gender when the Person is serialized back to the database
>> > > > > > (there's a UNIQUE constraint on GenderTbl.Gender, so this reverse
>> > > > > > lookup will be valid). I could just as easily do something like:
>> > > > > > private int gender;
>> > > > > > private Dictionary<int, string> genderForwardDict;
>> > > > > > private Dictionary<string, int> genderReverseDict;
>> > > > > > public string Gender
>> > > > > > {
>> > > > > > get{ return genderDict[gender];};
>> > > > > > set{ if (!genderReverseDict.ContainsKey(value)) throw new
>> > > > > > ArgumentException(); else gender = genderReverseDict[value];}
>>
>> > > > > > }
>>
>> > > > > > And I'd be fine with that. What I haven't figured out is how to
>> > > > > > get
>> > > > > > NHibernate to populate a static list of the legal values for the
>> > > > > > gender field (genderDict). Or is there some other way to do this
>> > > > > > that
>> > > > > > I'm missing? Specifically, I do this so view-related controls can
>> > > > > > bind to the list of legal values so the user can select from a
>> > > > > > combo
>> > > > > > box rather than having to perform a search every time or type in a
>> > > > > > string, etc.
>>
>> > > > > > Thanks!
>>
>> > > > > > ~Dathan
>>
>> > > --
>> > > Fabio Maulo
>>
>>
> >
>
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