Collection of subclass
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MSD
Aug 16, 2010, 8:23:05 AM8/16/10
to nhusers
I have the following classes:
public enum ContactValueType : short {...}
public abstract class ContactDetail
{
public int ID { get; protected set; }
public virtual ContactValueType ValueType { get; protected set; }
public virtual string Value { get; protected set; }
public ContactDetail(){}
public ContactDetail(ContactValueType valueType, string value)
{
this.ValueType = valueType;
this.Value = value;
}
}
public class StudentContactDetail : ContactDetail
{
public virtual Student Student { get; set; }
public StudentContactDetail(){}
public StudentContactDetail(Student student, ContactValueType
valueType, string value) : base(valueType, value)
{
this.Student = student;
}
}
public class EmployeeContactDetail : ContactDetail
{
public virtual Employee Employee { get; set; }
public EmployeeContactDetail(){}
public EmployeeContactDetail(Employee employee, ContactValueType
valueType, string value) : base(valueType, value)
{
this.Employee = employee;
}
}
public class Employee
{
public int ID { get; protected set; }
public virtual string Name { get; set; }
public virtual
Iesi.Collections.Generic.ISet<EmployeeContactDetail> ContactDetails
{ get; protected set; }
protected Employee()
{
ContactDetails = new
Iesi.Collections.Generic.HashedSet<EmployeeContactDetail>();
}
public Employee(string name) : this()
{
this.Name = name;
}
}
public class Student
{
public int ID { get; protected set; }
public virtual string Name { get; set; }
public virtual Iesi.Collections.Generic.ISet<StudentContactDetail>
ContactDetails { get; protected set; }
protected Student()
{
ContactDetails = new
Iesi.Collections.Generic.HashedSet<StudentContactDetail>();
}
public Student(string name): this()
{
this.Name = name;
}
}
their tables:
ContactDetail
ID int
EntityType char(1)
EntityID int
ValueType smallint
Value nvarchar(50)
Employee
ID int
Name nvarchar
Student
ID int
Name nvarchar
and their mappings:
<class name="ContactDetail" table="ContactDetail" lazy="false">
<id name="ID" column="ID">
<generator class="native"/>
</id>
<discriminator column="EntityType" type="String" />
<property name="ValueType" column="ValueType"/>
<property name="Value" column="Value"/>
<subclass name="StudentContactDetail" discriminator-value="S">
<many-to-one name="Student">
<column name="EntityID" />
</many-to-one>
</subclass>
<subclass name="EmployeeContactDetail" discriminator-value="E">
<many-to-one name="Employee">
<column name="EntityID" />
</many-to-one>
</subclass>
</class>
<class name="Student" table="Student" lazy="false">
<id name="ID">
<generator class="native"/>
</id>
<property name="Name">
<column name="Name" length="50" not-null="true" />
</property>
<set name="ContactDetails" fetch="select" lazy="false"
cascade="all">
<key column="EntityID" />
<one-to-many class="StudentContactDetail" />
</set>
</class>
<class name="Employee" table="Employee" lazy="false">
<id name="ID">
<generator class="native"/>
</id>
<property name="Name">
<column name="Name" length="50" not-null="true" />
</property>
<set name="ContactDetails" fetch="select" lazy="false"
cascade="all">
<key column="EntityID" />
<one-to-many class="EmployeeContactDetail" />
</set>
</class>
When persisting Student and Employee instances all is fine, but when
loading them, their ContactDetails collection is populated by ALL
ContactDetails, that is disregarding the discriminator in the select
statement.
Why is that and what can I do aside from this:
<set name="ContactDetails" fetch="select" lazy="false" cascade="all"
where="EntityType='E'">
(adding the where attribute).
Thanks
public enum ContactValueType : short {...}
public abstract class ContactDetail
{
public int ID { get; protected set; }
public virtual ContactValueType ValueType { get; protected set; }
public virtual string Value { get; protected set; }
public ContactDetail(){}
public ContactDetail(ContactValueType valueType, string value)
{
this.ValueType = valueType;
this.Value = value;
}
}
public class StudentContactDetail : ContactDetail
{
public virtual Student Student { get; set; }
public StudentContactDetail(){}
public StudentContactDetail(Student student, ContactValueType
valueType, string value) : base(valueType, value)
{
this.Student = student;
}
}
public class EmployeeContactDetail : ContactDetail
{
public virtual Employee Employee { get; set; }
public EmployeeContactDetail(){}
public EmployeeContactDetail(Employee employee, ContactValueType
valueType, string value) : base(valueType, value)
{
this.Employee = employee;
}
}
public class Employee
{
public int ID { get; protected set; }
public virtual string Name { get; set; }
public virtual
Iesi.Collections.Generic.ISet<EmployeeContactDetail> ContactDetails
{ get; protected set; }
protected Employee()
{
ContactDetails = new
Iesi.Collections.Generic.HashedSet<EmployeeContactDetail>();
}
public Employee(string name) : this()
{
this.Name = name;
}
}
public class Student
{
public int ID { get; protected set; }
public virtual string Name { get; set; }
public virtual Iesi.Collections.Generic.ISet<StudentContactDetail>
ContactDetails { get; protected set; }
protected Student()
{
ContactDetails = new
Iesi.Collections.Generic.HashedSet<StudentContactDetail>();
}
public Student(string name): this()
{
this.Name = name;
}
}
their tables:
ContactDetail
ID int
EntityType char(1)
EntityID int
ValueType smallint
Value nvarchar(50)
Employee
ID int
Name nvarchar
Student
ID int
Name nvarchar
and their mappings:
<class name="ContactDetail" table="ContactDetail" lazy="false">
<id name="ID" column="ID">
<generator class="native"/>
</id>
<discriminator column="EntityType" type="String" />
<property name="ValueType" column="ValueType"/>
<property name="Value" column="Value"/>
<subclass name="StudentContactDetail" discriminator-value="S">
<many-to-one name="Student">
<column name="EntityID" />
</many-to-one>
</subclass>
<subclass name="EmployeeContactDetail" discriminator-value="E">
<many-to-one name="Employee">
<column name="EntityID" />
</many-to-one>
</subclass>
</class>
<class name="Student" table="Student" lazy="false">
<id name="ID">
<generator class="native"/>
</id>
<property name="Name">
<column name="Name" length="50" not-null="true" />
</property>
<set name="ContactDetails" fetch="select" lazy="false"
cascade="all">
<key column="EntityID" />
<one-to-many class="StudentContactDetail" />
</set>
</class>
<class name="Employee" table="Employee" lazy="false">
<id name="ID">
<generator class="native"/>
</id>
<property name="Name">
<column name="Name" length="50" not-null="true" />
</property>
<set name="ContactDetails" fetch="select" lazy="false"
cascade="all">
<key column="EntityID" />
<one-to-many class="EmployeeContactDetail" />
</set>
</class>
When persisting Student and Employee instances all is fine, but when
loading them, their ContactDetails collection is populated by ALL
ContactDetails, that is disregarding the discriminator in the select
statement.
Why is that and what can I do aside from this:
<set name="ContactDetails" fetch="select" lazy="false" cascade="all"
where="EntityType='E'">
(adding the where attribute).
Thanks
Fabio Maulo
Aug 16, 2010, 8:33:15 AM8/16/10
to nhu...@googlegroups.com
various causes:
--
Fabio Maulo
1) your id (native) is unique in a class hierarchy (you have Employee#1 and Student#1)
2) you are using the same column (EntityID) for both reference in a table-per-class-hierarchy
3) you are lucky; have a look to FKs created for EntityID column
Solution:
use two different column-name for the relation
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--
Fabio Maulo
Message has been deleted
JideO
Aug 16, 2010, 3:00:09 PM8/16/10
to nhusers
MSD,
You decided to repost the solution I suggested to you on the earlier
topic: http://groups.google.com/group/nhusers/browse_thread/thread/1d2319f44...
as a different topic instead of continuing with the previous
discussion. You will make it difficult other people including myself
who were following the previous discussion to benefit from the
contribution from the community on the topic.
Apparently you have not properly implemented the mappings.
Jide
> > nhusers+u...@googlegroups.com<nhusers%2Bunsu...@googlegroups.com>
> > .
> Fabio Maulo- Hide quoted text -
>
> - Show quoted text -
You decided to repost the solution I suggested to you on the earlier
topic: http://groups.google.com/group/nhusers/browse_thread/thread/1d2319f44...
as a different topic instead of continuing with the previous
discussion. You will make it difficult other people including myself
who were following the previous discussion to benefit from the
contribution from the community on the topic.
Apparently you have not properly implemented the mappings.
Jide
> > .
> Fabio Maulo- Hide quoted text -
>
> - Show quoted text -
Muhammad Shehabeddeen
Aug 16, 2010, 3:23:02 PM8/16/10
to nhu...@googlegroups.com
Jide,
This implementation is different from the one in the other topic (it uses inheritance and a discriminator) and that is why I decided to post it in a separate question. This is one implementation suggested by a friend, and I was not asking how to implement the concept, I was just asking why the implementation was flawed. In anyway, I can link to it if necessary.
This implementation is different from the one in the other topic (it uses inheritance and a discriminator) and that is why I decided to post it in a separate question. This is one implementation suggested by a friend, and I was not asking how to implement the concept, I was just asking why the implementation was flawed. In anyway, I can link to it if necessary.
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Muhammad Shehabeddeen
Aug 16, 2010, 3:27:10 PM8/16/10
to nhu...@googlegroups.com
I re-checked what you had posted, and I agree you kind of mentioned inheritance in your post, but you did not show the design for the tables which is the real CATCH here since I am using a single column as a shared FK. Please correct me if the coffee has not kicked in yet :)
JideO
Aug 16, 2010, 6:55:53 PM8/16/10
to nhusers
I did not go beyond mentioning inheritance because I did not want to
influence your eventual implementation of the solution which I
suggested i.e. have a separate EntityContactInfo for each Entity that
uses the ContactInfo.
Inheritance is one of the ways to implement it. You could also use a
contained reference where the EntityContactInfo would have a reference
to the ContactInfo which would actually have avoided the problem you
ran into because you would have a separate mapping and table for each
EntityContactInfo. I initially thought there would be problems with a
bidirectional association with this approach but I'm not sure about
that anymore. However I still don't like that for each new
EntityContactInfo you have to touch the ContactInfo mapping to add the
new EntityContactInfo reverse mapping.
The above approach is virtually the same as using table-per-concrete-
class inheritance mapping which may actually be better.
The approach you tried to implement is the table-per-hierarchy for
which you will need a separate column in the ContactInfo table for
each Entity that uses ContactInfo and not one EntityID for all
entities as you attempted to do.
ContactInfo
ID int
EntityType char(1)
EmployeeID
CustomerID
SupplierID
....
ValueType smallint
Value nvarchar(50)
You can also use the other table-per-class at the expense of more
joins and other additional issues. However the weakness with the
inheritance approach is that you are basically mixing two separate
inheritance hierarchies which you'll see in the above and your table
definition where you have both EntityType and a ValueType columns in
the table. This basically means you have given up the choice of
extending by inheritance the types of ContactInfos you will have i.e.
PostalContactInfo, EmailContactInfo, PhoneContactInfo etc.
The containment approach avoids this mixup and allows you to extend
both ways.
I hope I have been specific enough without unduly influencing your
implementation. I would also like to see how your approach because it
may provide new ideas.
Jide
On Aug 16, 8:27 pm, Muhammad Shehabeddeen
> >> <nhusers%2Bunsu...@googlegroups.com<nhusers%252Bunsubscribe@googlegroups.com>
influence your eventual implementation of the solution which I
suggested i.e. have a separate EntityContactInfo for each Entity that
uses the ContactInfo.
Inheritance is one of the ways to implement it. You could also use a
contained reference where the EntityContactInfo would have a reference
to the ContactInfo which would actually have avoided the problem you
ran into because you would have a separate mapping and table for each
EntityContactInfo. I initially thought there would be problems with a
bidirectional association with this approach but I'm not sure about
that anymore. However I still don't like that for each new
EntityContactInfo you have to touch the ContactInfo mapping to add the
new EntityContactInfo reverse mapping.
The above approach is virtually the same as using table-per-concrete-
class inheritance mapping which may actually be better.
The approach you tried to implement is the table-per-hierarchy for
which you will need a separate column in the ContactInfo table for
each Entity that uses ContactInfo and not one EntityID for all
entities as you attempted to do.
ContactInfo
ID int
EntityType char(1)
EmployeeID
CustomerID
SupplierID
....
ValueType smallint
Value nvarchar(50)
You can also use the other table-per-class at the expense of more
joins and other additional issues. However the weakness with the
inheritance approach is that you are basically mixing two separate
inheritance hierarchies which you'll see in the above and your table
definition where you have both EntityType and a ValueType columns in
the table. This basically means you have given up the choice of
extending by inheritance the types of ContactInfos you will have i.e.
PostalContactInfo, EmailContactInfo, PhoneContactInfo etc.
The containment approach avoids this mixup and allows you to extend
both ways.
I hope I have been specific enough without unduly influencing your
implementation. I would also like to see how your approach because it
may provide new ideas.
Jide
On Aug 16, 8:27 pm, Muhammad Shehabeddeen
<muhammadshehabedd...@gmail.com> wrote:
> I re-checked what you had posted, and I agree you kind of mentioned
> inheritance in your post, but you did not show the design for the tables
> which is the real CATCH here since I am using a single column as a shared
> FK. Please correct me if the coffee has not kicked in yet :)
>
> On Mon, Aug 16, 2010 at 10:23 PM, Muhammad Shehabeddeen <
>
>
>
> muhammadshehabedd...@gmail.com> wrote:
> > Jide,
> > This implementation is different from the one in the other topic (it uses
> > inheritance and a discriminator) and that is why I decided to post it in a
> > separate question. This is one implementation suggested by a friend, and I
> > was not asking how to implement the concept, I was just asking why the
> > implementation was flawed. In anyway, I can link to it if necessary.
>
> I re-checked what you had posted, and I agree you kind of mentioned
> inheritance in your post, but you did not show the design for the tables
> which is the real CATCH here since I am using a single column as a shared
> FK. Please correct me if the coffee has not kicked in yet :)
>
> On Mon, Aug 16, 2010 at 10:23 PM, Muhammad Shehabeddeen <
>
>
>
> muhammadshehabedd...@gmail.com> wrote:
> > Jide,
> > This implementation is different from the one in the other topic (it uses
> > inheritance and a discriminator) and that is why I decided to post it in a
> > separate question. This is one implementation suggested by a friend, and I
> > was not asking how to implement the concept, I was just asking why the
> > implementation was flawed. In anyway, I can link to it if necessary.
>
> >> >
> >> > > .
> >> > > For more options, visit this group at
> >> > >http://groups.google.com/group/nhusers?hl=en.
>
> >> > --
> >> > Fabio Maulo- Hide quoted text -
>
> >> > - Show quoted text -
>
> >> --
> >> You received this message because you are subscribed to the Google Groups
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> >> To unsubscribe from this group, send email to
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> >> .
> >> For more options, visit this group at
> >>http://groups.google.com/group/nhusers?hl=en.- Hide quoted text -
> >> > > .
> >> > > For more options, visit this group at
> >> > >http://groups.google.com/group/nhusers?hl=en.
>
> >> > --
> >> > Fabio Maulo- Hide quoted text -
>
> >> > - Show quoted text -
>
> >> --
> >> You received this message because you are subscribed to the Google Groups
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> >> To unsubscribe from this group, send email to
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Muhammad Shehabeddeen
Aug 16, 2010, 9:01:01 PM8/16/10
to nhu...@googlegroups.com
Hey Jide,
You could also use a
contained reference where the EntityContactInfo would have a reference
to the ContactInfo which would actually have avoided the problem you
ran into because you would have a separate mapping and table for each
EntityContactInfo
The above approach is virtually the same as using table-per-concrete-
class inheritance mapping which may actually be better.
Table per concrete class mapping means 1 table and 1 mapping for EmployeeContactInfo and 1 table and 1 mapping for StudentContactInfo, no table nor mapping for the base class ContactInfo.
When you "would have a reference to the ContactInfo", do you mean that the subclasses EmployeeContactInfo and StudentContactInfo would have a property MyBaseContactInfo? I don't get it.
If on the other hand you mean by "reference" a foreign key, this has no place in a table per concrete class mapping since there is no table for the base class.
The containment approach avoids this mixup and allows you to extend
both ways.
I am still here assuming I understand what you mean by the "containment
approach" as the "table per concrete class" approach. How would that
solve the mixup? In that approach there would still be both EntityType and a ValueType columns.
Concerning which approach I am going for, I am more inclined to use a table per class hierarchy strategy, since I feel it is less of a fuss to add FKs to a table than add tables; but I am going to give it a bit more thought and compare the different options I have received. I really appreciate it, thanks.
Regards,
Concerning which approach I am going for, I am more inclined to use a table per class hierarchy strategy, since I feel it is less of a fuss to add FKs to a table than add tables; but I am going to give it a bit more thought and compare the different options I have received. I really appreciate it, thanks.
Regards,
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