Working with ENUM

Discussion in 'ASP .Net' started by Andrea Williams, Jun 2, 2004.

  1. I'm working with C# and I'm setting up some ENUM's I have a data and
    Business layer. I'm declaring a common enum for the Data Layer. The UI
    layer references the Bus layer and the bus layer references the Data layer,
    but I would like to have the enum exposed to all three. Is there a way to
    trickle down that enum (Like class inheritance exposes classes) so that it
    can be accessed from the Business layer and UI layers? My UI layer doesn't
    talk to the data layer directly and I would like to avoid having to set up
    the exact same enum in more than one of the layers.

    I hope this is making sense. Let me know if I need to explain some more.

    Thanks in advance,
    Andrea
    Andrea Williams, Jun 2, 2004
    #1
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  2. Andrea,

    Not sure if this was really the place to have posted this question, but
    assuming it isn't a crosspost then just this once I'm sure the moderator
    will take a leniant view :)

    Anyways there are obviously a number of ways of doing this, but one has to
    ask why the UI layer needs an enum that is declared and I assume used in the
    data layer, and the business layer from your question?

    I assume that the UI is providing a means for the client to manipulate data
    within an instance of a class? So once it is changed, the data becomes
    'dirty', is it this change you are trying to 'flag' by exposing a StatusFlag
    property as an ENUM?

    I am working on something at the moment and I have an ObjectStatus enum
    which is simply in it's own dll and I am referencing that from my ASP.NET UI
    layer, my domain model (business layer), and my repositories (data layers).
    If a value has changed then I simply mark the object 'dirty' by setting the
    status flag to ObjectStatus.osDirty.

    ObjectStatus is just declared as a public enum within the separate DLL.

    Once I finish reading Domain Driven Design by Eric Evans I may well change
    my mind.

    HTH
    Colin B


    "Andrea Williams" <> wrote in message
    news:e8Ka%...
    > I'm working with C# and I'm setting up some ENUM's I have a data and
    > Business layer. I'm declaring a common enum for the Data Layer. The UI
    > layer references the Bus layer and the bus layer references the Data

    layer,
    > but I would like to have the enum exposed to all three. Is there a way to
    > trickle down that enum (Like class inheritance exposes classes) so that it
    > can be accessed from the Business layer and UI layers? My UI layer

    doesn't
    > talk to the data layer directly and I would like to avoid having to set up
    > the exact same enum in more than one of the layers.
    >
    > I hope this is making sense. Let me know if I need to explain some more.
    >
    > Thanks in advance,
    > Andrea
    >
    >
    Colin Basterfield, Jun 2, 2004
    #2
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  3. Nope, no a cross-post, and it's for an ASP.NET app.

    In my UI, I have a search box that allows the user to search based on five
    different fields in a user record.

    namespace DAL
    {
    public enum SearchBy
    {
    FirstName,
    LastName,
    EmailAddress,
    SchoolOrg,
    Status
    }
    }

    I want to be able to pass a variable and use this in all the layers, but
    really the DataLayer is the one that handles the search. I figured that it
    would be handy to have these values in an ENUM instead of passing the field
    name, since it's only going to handle these particular fields. However, if
    I add the same enum to every layer, then if another field is added, I would
    need to update all the layers.

    So I guess my question is, what is the best way to pass this ENUM and only
    declare it in one place. Since the UI doesn't have access to the DAL, that
    doesn't seem like the best place, but the DAL isn't referencing any of the
    other layers and I don't want it to know or care about the BL or UIL. But I
    do want to make this enum available throughout the app.

    Any ideas?

    Andrea

    "Colin Basterfield" <> wrote in message
    news:...
    > Andrea,
    >
    > Not sure if this was really the place to have posted this question, but
    > assuming it isn't a crosspost then just this once I'm sure the moderator
    > will take a leniant view :)
    >
    > Anyways there are obviously a number of ways of doing this, but one has to
    > ask why the UI layer needs an enum that is declared and I assume used in

    the
    > data layer, and the business layer from your question?
    >
    > I assume that the UI is providing a means for the client to manipulate

    data
    > within an instance of a class? So once it is changed, the data becomes
    > 'dirty', is it this change you are trying to 'flag' by exposing a

    StatusFlag
    > property as an ENUM?
    >
    > I am working on something at the moment and I have an ObjectStatus enum
    > which is simply in it's own dll and I am referencing that from my ASP.NET

    UI
    > layer, my domain model (business layer), and my repositories (data

    layers).
    > If a value has changed then I simply mark the object 'dirty' by setting

    the
    > status flag to ObjectStatus.osDirty.
    >
    > ObjectStatus is just declared as a public enum within the separate DLL.
    >
    > Once I finish reading Domain Driven Design by Eric Evans I may well change
    > my mind.
    >
    > HTH
    > Colin B
    >
    >
    > "Andrea Williams" <> wrote in message
    > news:e8Ka%...
    > > I'm working with C# and I'm setting up some ENUM's I have a data and
    > > Business layer. I'm declaring a common enum for the Data Layer. The UI
    > > layer references the Bus layer and the bus layer references the Data

    > layer,
    > > but I would like to have the enum exposed to all three. Is there a way

    to
    > > trickle down that enum (Like class inheritance exposes classes) so that

    it
    > > can be accessed from the Business layer and UI layers? My UI layer

    > doesn't
    > > talk to the data layer directly and I would like to avoid having to set

    up
    > > the exact same enum in more than one of the layers.
    > >
    > > I hope this is making sense. Let me know if I need to explain some

    more.
    > >
    > > Thanks in advance,
    > > Andrea
    > >
    > >

    >
    >
    Andrea Williams, Jun 2, 2004
    #3
  4. Hi,

    On one hand I can see that this is indeed a workable approach if you
    introduce a separate assembly to hold the ENUM.

    However, and you can ignore this if you like or are too far down the track,
    but you really ought to read Patterns of Enterprise Appplication
    Architecture by Martin Fowler, because within here there is another approach
    which is far cleaner and flexible, IMHO anyways, and that is to introduce
    the idea of a Criteria class which one can use singularly or as part of a
    list of Criteria to construct the ultimate query passed to the database.

    This makes use of an overall Repository pattern object, which uses both
    MetaData Mapping, and the Query Object underneath, so the client can
    stipulate which fields of the class are to be used by inserting them into a
    criteria object which is then passed to the Repository, and then in the
    Criteria class you could attach all kinds of different things like equal.

    So to work it to your requirement you could have a ClientRepository and one
    of it's methods could be to create a list of all the clients whose
    attributes are made up of 1..n search criteria, so in your application
    coordinator, you could do, and this a bit of a hack but hopefully helps you
    to understand what I burbling on about:

    CriteriaList critList = new CriteriaList();
    if txtFirstName.Text != ""
    {
    Criteria fnCriteria = new Criteria()
    criteria.Equals(Client.FirstName, txtFirstName.Text)
    critList.Add(fnCriteria)
    }
    etc...

    Then you could do:

    ClientRepository clientRep = new ClientRepository()
    ClientList clientList = clientRep.Matching(critList)

    Now within the ClientRepository you would implement the Matching method, and
    it would have access to some kind of Client mapper class so it could find
    the actual field name of Client.FirstName, and that would be used along with
    the Criteria object to create an actual query object so that you ended up
    with

    select * from client where first_name = @firstName

    where @firstName is set to whatever txtFirstName.Text.

    Assuming you use Test Driven Development, and NUnit, you would implement an
    in memory client list, that you loaded from an XML file or something, and
    then use NUnit to test the internals of your client repository and the rest
    eliminating both the ASP.NET UI, and the database.

    There are lots of holes in this text, and I am sure I have glossed over bits
    of it, unfortunately so does Mr Fowler occasionally, however as he says
    tehre is no turnkey solution, but one thing I have learnt is that by using
    TDD, NUnit and tiny steps it evolves into something great.

    FWIW
    Colin

    "Andrea Williams" <> wrote in message
    news:...
    > Nope, no a cross-post, and it's for an ASP.NET app.
    >
    > In my UI, I have a search box that allows the user to search based on five
    > different fields in a user record.
    >
    > namespace DAL
    > {
    > public enum SearchBy
    > {
    > FirstName,
    > LastName,
    > EmailAddress,
    > SchoolOrg,
    > Status
    > }
    > }
    >
    > I want to be able to pass a variable and use this in all the layers, but
    > really the DataLayer is the one that handles the search. I figured that

    it
    > would be handy to have these values in an ENUM instead of passing the

    field
    > name, since it's only going to handle these particular fields. However,

    if
    > I add the same enum to every layer, then if another field is added, I

    would
    > need to update all the layers.
    >
    > So I guess my question is, what is the best way to pass this ENUM and only
    > declare it in one place. Since the UI doesn't have access to the DAL,

    that
    > doesn't seem like the best place, but the DAL isn't referencing any of the
    > other layers and I don't want it to know or care about the BL or UIL. But

    I
    > do want to make this enum available throughout the app.
    >
    > Any ideas?
    >
    > Andrea
    >
    > "Colin Basterfield" <> wrote in message
    > news:...
    > > Andrea,
    > >
    > > Not sure if this was really the place to have posted this question, but
    > > assuming it isn't a crosspost then just this once I'm sure the moderator
    > > will take a leniant view :)
    > >
    > > Anyways there are obviously a number of ways of doing this, but one has

    to
    > > ask why the UI layer needs an enum that is declared and I assume used in

    > the
    > > data layer, and the business layer from your question?
    > >
    > > I assume that the UI is providing a means for the client to manipulate

    > data
    > > within an instance of a class? So once it is changed, the data becomes
    > > 'dirty', is it this change you are trying to 'flag' by exposing a

    > StatusFlag
    > > property as an ENUM?
    > >
    > > I am working on something at the moment and I have an ObjectStatus enum
    > > which is simply in it's own dll and I am referencing that from my

    ASP.NET
    > UI
    > > layer, my domain model (business layer), and my repositories (data

    > layers).
    > > If a value has changed then I simply mark the object 'dirty' by setting

    > the
    > > status flag to ObjectStatus.osDirty.
    > >
    > > ObjectStatus is just declared as a public enum within the separate DLL.
    > >
    > > Once I finish reading Domain Driven Design by Eric Evans I may well

    change
    > > my mind.
    > >
    > > HTH
    > > Colin B
    > >
    > >
    > > "Andrea Williams" <> wrote in message
    > > news:e8Ka%...
    > > > I'm working with C# and I'm setting up some ENUM's I have a data and
    > > > Business layer. I'm declaring a common enum for the Data Layer. The

    UI
    > > > layer references the Bus layer and the bus layer references the Data

    > > layer,
    > > > but I would like to have the enum exposed to all three. Is there a way

    > to
    > > > trickle down that enum (Like class inheritance exposes classes) so

    that
    > it
    > > > can be accessed from the Business layer and UI layers? My UI layer

    > > doesn't
    > > > talk to the data layer directly and I would like to avoid having to

    set
    > up
    > > > the exact same enum in more than one of the layers.
    > > >
    > > > I hope this is making sense. Let me know if I need to explain some

    > more.
    > > >
    > > > Thanks in advance,
    > > > Andrea
    > > >
    > > >

    > >
    > >

    >
    >
    Colin Basterfield, Jun 3, 2004
    #4
  5. I would create another assembly (i.e. Common) that all other layers
    reference(DAL,BL,UI...), and put in there the common structures, constants
    and enums.

    Lennin
    Lennin Arriola, Jun 3, 2004
    #5
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