I just started using the Entity Framework recently to employ persistence
for an already established code base. Initially I was using the "Model
& Database First" paradigm where a designer is used to layout the data
model. Although, this ended up being tedious since my
POCO instance had
to exactly match the POCO
proxy instance
in my model designer view. After upgrading to EF 4.1, I realized the
"Code First"
paradigm
was the way to go since I had to adapt the persistence model to my
already existing code.
One of the earliest problems that I ran into was having more than one
property on a class that referenced the same class type. This example
was taken from a great
site
that explored the different EF properties.
[]{.Apple-style-span
style=“background-color: #f8f8f8; color: #2e2e2e; font-family: ‘Courier New’, Courier, mono; font-size: 12px;”}\
public class Customer
{
public int Id { get; set; }
public int Age { get; set; }
public Address BillingAddress { get; set; }
public Address DeliveryAddress { get; set; }
}
Notice how both the [BillingAddress ]{.Apple-style-span
style=“background-color: #f8f8f8; color: #2e2e2e; font-family: monospace; font-size: 12px; white-space: pre;"}and [DeliveryAddress
]{.Apple-style-span
style=“background-color: #f8f8f8; color: #2e2e2e; font-family: monospace; font-size: 12px; white-space: pre;"}properties
references the same class type. I kept trying to establish two 1-to-1
relationships on the class but this caused a problem with cascading
deletes and foreign key constraints. I found a
solution but
it still required exceptional behavior on the part of my context and the
database schema.
The most elegant solution was to just treat both of the properties as
complex
types.
The only thing I had to do was remove the [Id ]{.Apple-style-span
style=“background-color: #f8f8f8; color: #2e2e2e; font-family: monospace; font-size: 12px; white-space: pre;"}property
from the properties' class and the context took care of the rest. So
instead of two tables in the database (one for [Customer
]{.Apple-style-span
style=“font-family: monospace; font-size: 12px; white-space: pre;"}and
the other for [Address]{.Apple-style-span
style=“font-family: monospace; font-size: 12px; white-space: pre;”}),
there would be only one. Below is a layout of what the table would look
like.
\
Customer
{
Id
Age
BillingAddress_City
BillingAddress_Street
BillingAddress_Zipcode
DeliveryAddress_City
DeliveryAddress_Street
DeliveryAddress_Zipcode
}
\