> I'm converting an app written in VB 2003 to 2005 and need advice for how to
> deal with this situation:
>
> The app has a number of "manager" classes that handle the data access.  They
> all have several routines that are identical, except for the object type and
> database action specific to that particular class, such as "Public ReadOnly
> Property Item(ByVal SystemID As Integer) As CEmployee" or "Public Shared
> Function Save(ByVal TheItem As CEmployee) As Boolean".  Each of the object
> classes also have a bunch of common properties and methods that are
> inherited from an abstract base class.
>
> What I want to do with the manager classes is rewrite them using an abstract
> class with MustOverride properties and methods.  Where I'm hung up is the
> existing implementation uses an Enum that defines the database field names
> and ordinal positions in the SELECT statement used to create the datareader.
> For example:
>
> Public Class EmployeeManager
>
>   Public Enum MyFields
>     NameSystemID = 0
>     NameFirst
>     NameMiddle
>     NameLast
>     DateHired
>     RecStatus
>     RecDateAdd
>     RecDateRev
>     RecAddBy
>     RecRevBy
>   End Enum
>
>   Private Shared _FieldList As ArrayList = Nothing
>   Public Shared ReadOnly Property FieldList() As ArrayList
>     Get
>       If _FieldList Is Nothing Then
>         _FieldList = New ArrayList
>         Dim arNames() As String
>         arNames = MyFields.GetNames(GetType(MyFields))
>         For x As Integer = 0 To arNames.GetUpperBound(0)
>           _FieldList.Add(New VisarEnumBindingItem(EnumValue:=x,
> EnumLabel:=arNames(x))
>         Next
>       End If
>       Return _FieldList
>     End Get
>   End Property
>
>   Private Shared _FieldListString As String = ""
>   Public Shared ReadOnly Property FieldListString() As String
>     Get
>       If _FieldListString = "" Then
>         Dim ThisItem As VisarEnumBindingItem = Nothing
>         For x As Integer = 0 To FieldList.Count -1
>           ThisItem = CType(_FieldList(x), VisarEnumBindingItem)
>           _FieldListString += ThisItem.StringValue & ", "
>         Next
>         _FieldListString = Left(_FieldListString,
> _FieldListString.LastIndexOf(", "))
>       End If
>       Return _FieldListString
>     End Get
>   End Property
>
>   ' Overloaded Item property creates a command to retrieve by PK or AK,
> passes command to ItemFetch, which in turn calls ItemFill to unpack the
> datareader into the instance object and pass it back up the chain.
>
>   Private Shared Function ItemFill(ByVal ItemReader As OleDbDataReader) As
> CEmployee
>     With ItemReader
>         Return New CEmployee(RecSystemID:=.GetInt32(MyFields.NameSystemID),
> RecStatus:=VisarGoodies.MakeInt32(.GetValue(MyFields.RecStatus)),
> RecDateAdd:=VisarGoodies.MakeDate(.GetValue(MyFields.RecDateAdd)),
> RecDateRev:=VisarGoodies.MakeDate(.GetValue(MyFields.RecDateRev)),
> RecAddBy:=VisarGoodies.MakeInt32(.GetValue(MyFields.RecAddBy)),
> RecRevBy:=VisarGoodies.MakeInt32(.GetValue(MyFields.RecRevBy)),
> NameFirst:=VisarGoodies.MakeString(.GetValue(MyFields.NameFirst)),
> NameMiddle:=VisarGoodies.MakeString(.GetValue(MyFields.NameMiddle)),
> NameLast:=VisarGoodies.MakeString(.GetValue(MyFields.NameLast)))
>     End With
>   End Function
>
> End Class
>
> The way it's designed, changes to the order of fields in the select
> statement or even actual field names only need to be made in the Enum.  The
> select, insert, and update statements are dynamically constructed in each of
> the managers from the FieldList arraylist.
>
> How can I create the identical functionality using an abstract class in
> VB2005, also placing the code that constructs the "FieldList" from the Enum
> into a shared method in a separate utility class?  I tried using a
> placeholder enum and the FieldList property in the base class, and a
> shadowed enum in a derived class, but when executed, it uses the base enum,
> not the shadowed one.  It does work when place the enum and override
> FieldList in each of the derived classes but I don't want to implement
> identical code over and over.
>
> Thanks,
>
> Gino

"Izzy" <israel.rich***@gmail.com> wrote in message
news:1153336768.640345.77960@p79g2000cwp.googlegroups.com...
> Well I'm confused.....
>
> Is all this just for the purpose of selecting, updating, inserting
> records to and from a database?
>
> If so then I'd say this is in major need of a rewrite. Why make things
> harder than they need to be?
>
>
> Confused Newbie wrote:
>> I'm converting an app written in VB 2003 to 2005 and need advice for how
>> to
>> deal with this situation:
>>
>> The app has a number of "manager" classes that handle the data access.
>> They
>> all have several routines that are identical, except for the object type
>> and
>> database action specific to that particular class, such as "Public
>> ReadOnly
>> Property Item(ByVal SystemID As Integer) As CEmployee" or "Public Shared
>> Function Save(ByVal TheItem As CEmployee) As Boolean".  Each of the
>> object
>> classes also have a bunch of common properties and methods that are
>> inherited from an abstract base class.
>>
>> What I want to do with the manager classes is rewrite them using an
>> abstract
>> class with MustOverride properties and methods.  Where I'm hung up is the
>> existing implementation uses an Enum that defines the database field
>> names
>> and ordinal positions in the SELECT statement used to create the
>> datareader.
>> For example:
>>
>> Public Class EmployeeManager
>>
>>   Public Enum MyFields
>>     NameSystemID = 0
>>     NameFirst
>>     NameMiddle
>>     NameLast
>>     DateHired
>>     RecStatus
>>     RecDateAdd
>>     RecDateRev
>>     RecAddBy
>>     RecRevBy
>>   End Enum
>>
>>   Private Shared _FieldList As ArrayList = Nothing
>>   Public Shared ReadOnly Property FieldList() As ArrayList
>>     Get
>>       If _FieldList Is Nothing Then
>>         _FieldList = New ArrayList
>>         Dim arNames() As String
>>         arNames = MyFields.GetNames(GetType(MyFields))
>>         For x As Integer = 0 To arNames.GetUpperBound(0)
>>           _FieldList.Add(New VisarEnumBindingItem(EnumValue:=x,
>> EnumLabel:=arNames(x))
>>         Next
>>       End If
>>       Return _FieldList
>>     End Get
>>   End Property
>>
>>   Private Shared _FieldListString As String = ""
>>   Public Shared ReadOnly Property FieldListString() As String
>>     Get
>>       If _FieldListString = "" Then
>>         Dim ThisItem As VisarEnumBindingItem = Nothing
>>         For x As Integer = 0 To FieldList.Count -1
>>           ThisItem = CType(_FieldList(x), VisarEnumBindingItem)
>>           _FieldListString += ThisItem.StringValue & ", "
>>         Next
>>         _FieldListString = Left(_FieldListString,
>> _FieldListString.LastIndexOf(", "))
>>       End If
>>       Return _FieldListString
>>     End Get
>>   End Property
>>
>>   ' Overloaded Item property creates a command to retrieve by PK or AK,
>> passes command to ItemFetch, which in turn calls ItemFill to unpack the
>> datareader into the instance object and pass it back up the chain.
>>
>>   Private Shared Function ItemFill(ByVal ItemReader As OleDbDataReader)
>> As
>> CEmployee
>>     With ItemReader
>>         Return New
>> CEmployee(RecSystemID:=.GetInt32(MyFields.NameSystemID),
>> RecStatus:=VisarGoodies.MakeInt32(.GetValue(MyFields.RecStatus)),
>> RecDateAdd:=VisarGoodies.MakeDate(.GetValue(MyFields.RecDateAdd)),
>> RecDateRev:=VisarGoodies.MakeDate(.GetValue(MyFields.RecDateRev)),
>> RecAddBy:=VisarGoodies.MakeInt32(.GetValue(MyFields.RecAddBy)),
>> RecRevBy:=VisarGoodies.MakeInt32(.GetValue(MyFields.RecRevBy)),
>> NameFirst:=VisarGoodies.MakeString(.GetValue(MyFields.NameFirst)),
>> NameMiddle:=VisarGoodies.MakeString(.GetValue(MyFields.NameMiddle)),
>> NameLast:=VisarGoodies.MakeString(.GetValue(MyFields.NameLast)))
>>     End With
>>   End Function
>>
>> End Class
>>
>> The way it's designed, changes to the order of fields in the select
>> statement or even actual field names only need to be made in the Enum.
>> The
>> select, insert, and update statements are dynamically constructed in each
>> of
>> the managers from the FieldList arraylist.
>>
>> How can I create the identical functionality using an abstract class in
>> VB2005, also placing the code that constructs the "FieldList" from the
>> Enum
>> into a shared method in a separate utility class?  I tried using a
>> placeholder enum and the FieldList property in the base class, and a
>> shadowed enum in a derived class, but when executed, it uses the base
>> enum,
>> not the shadowed one.  It does work when place the enum and override
>> FieldList in each of the derived classes but I don't want to implement
>> identical code over and over.
>>
>> Thanks,
>>
>> Gino
>

"Confused Newbie" <nope@spam.duh> wrote in message
news:uUz5IF2qGHA.3648@TK2MSFTNGP03.phx.gbl...
| I'm converting an app written in VB 2003 to 2005 and need advice for how
to
| deal with this situation:
|
| The app has a number of "manager" classes that handle the data access.
They
| all have several routines that are identical, except for the object type
and
| database action specific to that particular class, such as "Public
ReadOnly
| Property Item(ByVal SystemID As Integer) As CEmployee" or "Public Shared
| Function Save(ByVal TheItem As CEmployee) As Boolean".  Each of the object
| classes also have a bunch of common properties and methods that are
| inherited from an abstract base class.
|
| What I want to do with the manager classes is rewrite them using an
abstract
| class with MustOverride properties and methods.  Where I'm hung up is the
| existing implementation uses an Enum that defines the database field names
| and ordinal positions in the SELECT statement used to create the
datareader.
| For example:
|
| Public Class EmployeeManager
|
|  Public Enum MyFields
|    NameSystemID = 0
|    NameFirst
|    NameMiddle
|    NameLast
|    DateHired
|    RecStatus
|    RecDateAdd
|    RecDateRev
|    RecAddBy
|    RecRevBy
|  End Enum
|
|  Private Shared _FieldList As ArrayList = Nothing
|  Public Shared ReadOnly Property FieldList() As ArrayList
|    Get
|      If _FieldList Is Nothing Then
|        _FieldList = New ArrayList
|        Dim arNames() As String
|        arNames = MyFields.GetNames(GetType(MyFields))
|        For x As Integer = 0 To arNames.GetUpperBound(0)
|          _FieldList.Add(New VisarEnumBindingItem(EnumValue:=x,
| EnumLabel:=arNames(x))
|        Next
|      End If
|      Return _FieldList
|    End Get
|  End Property
|
|  Private Shared _FieldListString As String = ""
|  Public Shared ReadOnly Property FieldListString() As String
|    Get
|      If _FieldListString = "" Then
|        Dim ThisItem As VisarEnumBindingItem = Nothing
|        For x As Integer = 0 To FieldList.Count -1
|          ThisItem = CType(_FieldList(x), VisarEnumBindingItem)
|          _FieldListString += ThisItem.StringValue & ", "
|        Next
|        _FieldListString = Left(_FieldListString,
| _FieldListString.LastIndexOf(", "))
|      End If
|      Return _FieldListString
|    End Get
|  End Property
|
|  ' Overloaded Item property creates a command to retrieve by PK or AK,
| passes command to ItemFetch, which in turn calls ItemFill to unpack the
| datareader into the instance object and pass it back up the chain.
|
|  Private Shared Function ItemFill(ByVal ItemReader As OleDbDataReader) As
| CEmployee
|    With ItemReader
|        Return New CEmployee(RecSystemID:=.GetInt32(MyFields.NameSystemID),
| RecStatus:=VisarGoodies.MakeInt32(.GetValue(MyFields.RecStatus)),
| RecDateAdd:=VisarGoodies.MakeDate(.GetValue(MyFields.RecDateAdd)),
| RecDateRev:=VisarGoodies.MakeDate(.GetValue(MyFields.RecDateRev)),
| RecAddBy:=VisarGoodies.MakeInt32(.GetValue(MyFields.RecAddBy)),
| RecRevBy:=VisarGoodies.MakeInt32(.GetValue(MyFields.RecRevBy)),
| NameFirst:=VisarGoodies.MakeString(.GetValue(MyFields.NameFirst)),
| NameMiddle:=VisarGoodies.MakeString(.GetValue(MyFields.NameMiddle)),
| NameLast:=VisarGoodies.MakeString(.GetValue(MyFields.NameLast)))
|    End With
|  End Function
|
| End Class
|
| The way it's designed, changes to the order of fields in the select
| statement or even actual field names only need to be made in the Enum.
The
| select, insert, and update statements are dynamically constructed in each
of
| the managers from the FieldList arraylist.
|
| How can I create the identical functionality using an abstract class in
| VB2005, also placing the code that constructs the "FieldList" from the
Enum
| into a shared method in a separate utility class?  I tried using a
| placeholder enum and the FieldList property in the base class, and a
| shadowed enum in a derived class, but when executed, it uses the base
enum,
| not the shadowed one.  It does work when place the enum and override
| FieldList in each of the derived classes but I don't want to implement
| identical code over and over.
|
| Thanks,
|
| Gino
|
|

"Jay B. Harlow [MVP - Outlook]" <Jay_Harlow_***@tsbradley.net> wrote in
message news:%23i2Ez64qGHA.5008@TK2MSFTNGP05.phx.gbl...
> Confused Newbie,
> I would consider using a Generic class, passing the Enum & object type as
> type parameters
>
> Something like:
>
>    Dim employeManager as New Manager(Of Employee, Employee.MyFields)
>
> The "trick" is the implementation of ItemFill, as you need the constructor
> to Employee, generally I make Manager a base class...
>
> Alternatively you could define "Manager" as a shared member of Employee
> itself:
>
>    Public Class Employee
>
>        Public Shared ReadOnly Manager As New EmployeeManager()
>
>        Public Enum MyFields
>            NameSystemID = 0
>            NameFirst
>            NameMiddle
>            NameLast
>            DateHired
>            RecStatus
>            RecDateAdd
>            RecDateRev
>            RecAddBy
>            RecRevBy
>        End Enum
>
>    End Class
>
>    Public Class EmployeeManager
>        Inherits Manager(Of Employee, Employee.MyFields)
>
>    End Class
>
> Where Manager is defined something like:
>
>    Public MustInherit Class Manager(Of T As Class, F)
>
>        Private _FieldList As ArrayList = Nothing
>        Public ReadOnly Property FieldList() As ArrayList
>            Get
>                If _FieldList Is Nothing Then
>                    _FieldList = New ArrayList
>                    Dim arNames() As String
>                    arNames = [Enum].GetNames(GetType(F))
>                    For x As Integer = 0 To arNames.GetUpperBound(0)
>                        _FieldList.Add(New
> VisarEnumBindingItem(EnumValue:=x, EnumLabel:=arNames(x)))
>                    Next
>                End If
>                Return _FieldList
>            End Get
>        End Property
>
>        Private _FieldListString As String = ""
>        Public ReadOnly Property FieldListString() As String
>            Get
>                If _FieldListString = "" Then
>                    Dim ThisItem As VisarEnumBindingItem = Nothing
>                    For x As Integer = 0 To FieldList.Count - 1
>                        ThisItem = CType(_FieldList(x),
> VisarEnumBindingItem)
>                        _FieldListString += ThisItem.StringValue & ", "
>                    Next
>                    _FieldListString = Left(_FieldListString,
> _FieldListString.LastIndexOf(", "))
>                End If
>                Return _FieldListString
>            End Get
>        End Property
>
>        Public MustOverride Function ItemFill(ByVal ItemReader As
> OleDbDataReader) As T
>
>    End Class
>
> --
> Hope this helps
> Jay B. Harlow [MVP - Outlook]
> .NET Application Architect, Enthusiast, & Evangelist
> T.S. Bradley - http://www.tsbradley.net
>
>
> "Confused Newbie" <nope@spam.duh> wrote in message
> news:uUz5IF2qGHA.3648@TK2MSFTNGP03.phx.gbl...
> | I'm converting an app written in VB 2003 to 2005 and need advice for how
> to
> | deal with this situation:
> |
> | The app has a number of "manager" classes that handle the data access.
> They
> | all have several routines that are identical, except for the object type
> and
> | database action specific to that particular class, such as "Public
> ReadOnly
> | Property Item(ByVal SystemID As Integer) As CEmployee" or "Public Shared
> | Function Save(ByVal TheItem As CEmployee) As Boolean".  Each of the
> object
> | classes also have a bunch of common properties and methods that are
> | inherited from an abstract base class.
> |
> | What I want to do with the manager classes is rewrite them using an
> abstract
> | class with MustOverride properties and methods.  Where I'm hung up is
> the
> | existing implementation uses an Enum that defines the database field
> names
> | and ordinal positions in the SELECT statement used to create the
> datareader.
> | For example:
> |
> | Public Class EmployeeManager
> |
> |  Public Enum MyFields
> |    NameSystemID = 0
> |    NameFirst
> |    NameMiddle
> |    NameLast
> |    DateHired
> |    RecStatus
> |    RecDateAdd
> |    RecDateRev
> |    RecAddBy
> |    RecRevBy
> |  End Enum
> |
> |  Private Shared _FieldList As ArrayList = Nothing
> |  Public Shared ReadOnly Property FieldList() As ArrayList
> |    Get
> |      If _FieldList Is Nothing Then
> |        _FieldList = New ArrayList
> |        Dim arNames() As String
> |        arNames = MyFields.GetNames(GetType(MyFields))
> |        For x As Integer = 0 To arNames.GetUpperBound(0)
> |          _FieldList.Add(New VisarEnumBindingItem(EnumValue:=x,
> | EnumLabel:=arNames(x))
> |        Next
> |      End If
> |      Return _FieldList
> |    End Get
> |  End Property
> |
> |  Private Shared _FieldListString As String = ""
> |  Public Shared ReadOnly Property FieldListString() As String
> |    Get
> |      If _FieldListString = "" Then
> |        Dim ThisItem As VisarEnumBindingItem = Nothing
> |        For x As Integer = 0 To FieldList.Count -1
> |          ThisItem = CType(_FieldList(x), VisarEnumBindingItem)
> |          _FieldListString += ThisItem.StringValue & ", "
> |        Next
> |        _FieldListString = Left(_FieldListString,
> | _FieldListString.LastIndexOf(", "))
> |      End If
> |      Return _FieldListString
> |    End Get
> |  End Property
> |
> |  ' Overloaded Item property creates a command to retrieve by PK or AK,
> | passes command to ItemFetch, which in turn calls ItemFill to unpack the
> | datareader into the instance object and pass it back up the chain.
> |
> |  Private Shared Function ItemFill(ByVal ItemReader As OleDbDataReader)
> As
> | CEmployee
> |    With ItemReader
> |        Return New
> CEmployee(RecSystemID:=.GetInt32(MyFields.NameSystemID),
> | RecStatus:=VisarGoodies.MakeInt32(.GetValue(MyFields.RecStatus)),
> | RecDateAdd:=VisarGoodies.MakeDate(.GetValue(MyFields.RecDateAdd)),
> | RecDateRev:=VisarGoodies.MakeDate(.GetValue(MyFields.RecDateRev)),
> | RecAddBy:=VisarGoodies.MakeInt32(.GetValue(MyFields.RecAddBy)),
> | RecRevBy:=VisarGoodies.MakeInt32(.GetValue(MyFields.RecRevBy)),
> | NameFirst:=VisarGoodies.MakeString(.GetValue(MyFields.NameFirst)),
> | NameMiddle:=VisarGoodies.MakeString(.GetValue(MyFields.NameMiddle)),
> | NameLast:=VisarGoodies.MakeString(.GetValue(MyFields.NameLast)))
> |    End With
> |  End Function
> |
> | End Class
> |
> | The way it's designed, changes to the order of fields in the select
> | statement or even actual field names only need to be made in the Enum.
> The
> | select, insert, and update statements are dynamically constructed in
> each
> of
> | the managers from the FieldList arraylist.
> |
> | How can I create the identical functionality using an abstract class in
> | VB2005, also placing the code that constructs the "FieldList" from the
> Enum
> | into a shared method in a separate utility class?  I tried using a
> | placeholder enum and the FieldList property in the base class, and a
> | shadowed enum in a derived class, but when executed, it uses the base
> enum,
> | not the shadowed one.  It does work when place the enum and override
> | FieldList in each of the derived classes but I don't want to implement
> | identical code over and over.
> |
> | Thanks,
> |
> | Gino
> |
> |
>
>