Go Premium for a chance to win a PS4. Enter to Win

x
  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 465
  • Last Modified:

Entity Framework doesn't update Many to Many relation

Hi Experts,

I have the following tables in an SQL2008 database:

Accommodation
code	varchar(18)
name	varchar(80)

Open in new window

This table has more columns but i have removed them here for simplicity.

Attributes
code	int
name	varchar(50)

Open in new window

     
AccommodationAttributes
AccommodationCode	varchar(18)
AttributeCode	int

Open in new window


As you may get, AccommodationAttributes describes the many to many relationship between Accommodations and Attributes.

I have created my model (EF5) using database first, and it has created two classes linked with a navigation property.

All this seems correct.

What i am trying to do is add values in the db, but though i am able to add Accommodations and Attributes, i don't seem to be able to make it add the corresponding values in the AccommodationAttributes table.

I am reading from an XML file.
Bellow is a code sample of what i am trying to do.

var Accommodations = from a in xe.Elements("accommodation") select a;
foreach (var accommodation in Accommodations)
{
   var AccCode = accommodation.Element("code").Value;
   Accommodation a = context.Accommodations.Where(x=>x.code == AccCode).SingleOrDefault();
   bool newAccommodation = a == null ? true : false;
   a = !newAccommodation ? a :
      new Accommodation
      {
          code = accommodation.Element("code") == null ? null : accommodation.Element("code").Value,
          name = accommodation.Element("name") == null ? null : accommodation.Element("name").Value
      };
      foreach (var attribute in accommodation.Elements("attributes").Elements("attribute").Select(x=>x.Value))
      {
         Attribute at = context.Attributes.Where(x => x.name == attribute).SingleOrDefault();
         a.Attributes.Add(at);
      }
      context.SaveChanges();
}

Open in new window


After running this code i Run the following in SQL:
select COUNT(*) from Accommodations
select COUNT(*)from Attributes
select COUNT(*)from AccommodationAttributes

Open in new window


But though i see entries in the two tables, the link table comes with 0 rows.

I have tried other variations, like attaching the objects to the context, or implicitly specifying that it is a modified object.

By the time that this code will run i am sure that the Attributes are allready inserted in the db, but the Accommodation is either an Insert or Update.

I am eager to hear your thoughts,

Giannis
0
Ioannis Paraskevopoulos
Asked:
Ioannis Paraskevopoulos
  • 6
  • 4
1 Solution
 
jorge_torizCommented:
I did it with this code and everything worked so fine :s

EFModel.ExpertsExchangeEntities db = new EFModel.ExpertsExchangeEntities();
EFModel.Accommodation myAccommodation = new EFModel.Accommodation();
myAccommodation.Code = "Acc01";
myAccommodation.Name = "Accommodation 01";

myAccommodation.Attributes.Add(new EFModel.Attribute()
{
    Code = 1,
    Name = "Attribute 1"
});

myAccommodation.Attributes.Add(new EFModel.Attribute()
{
    Code = 2,
    Name = "Attribute 2"
});

db.AddToAccommodations(myAccommodation);

db.SaveChanges();

Open in new window

0
 
Ioannis ParaskevopoulosAuthor Commented:
Hi,

Thanks for the response...
Can you please elaborate a little bit?

Is db the context in my example?
I don't have a method AddToAccommodations.

Giannis
0
 
jorge_torizCommented:
your "context" variable is my "db" variable, the method AddToAccommodations was generated by the Entity Framework wizard.

I'm attaching the project in this reply.

I renamed the file EFModel\EE.edmx to EFModel\EE.txt to be able to send you the project in the zip, just fix the extension and the project should run without problems.
Project.zip
0
Concerto's Cloud Advisory Services

Want to avoid the missteps to gaining all the benefits of the cloud? Learn more about the different assessment options from our Cloud Advisory team.

 
Ioannis ParaskevopoulosAuthor Commented:
Hi,

I do see that in your project. One question, is that EF4? I am using EF5.

Giannis
0
 
jorge_torizCommented:
Yes, I'm working with 4 :s
0
 
Ioannis ParaskevopoulosAuthor Commented:
Is it possible that EF4 is somewhat different from EF5 in that manner?
0
 
jorge_torizCommented:
I'm really sorry pal, I haven't worked on EF5, but let me search something about many to may relationships in EF5 and verify if there is something different that you must take care of
0
 
Ioannis ParaskevopoulosAuthor Commented:
Hi,

After further investigation, it seems that it works when i add a new Accommodation, but it fails when the Accommodation is already in the db and i just add new attributes. In my case in the process of developing i had first added the Accommodation and in a later step of development i created the process to import attributes. So i need to find a way to update the relationship when both accommodation and  attribute are already in the db. Thanks for the help.

Giannis
0
 
Ioannis ParaskevopoulosAuthor Commented:
I found the solution...The problem was i had set the AutoDetectChangesEnabled to False. When i commented out this line it worked. I am marking the answer as accepted because it was correct in its core and the expert could not know my settings due to information provided.

Thanks a lot for the help, even indirectly it helped me get the solution i needed.

Giannis
0
 
Ioannis ParaskevopoulosAuthor Commented:
Thanks a lot for your help and patience.

Giannis
0

Featured Post

Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

  • 6
  • 4
Tackle projects and never again get stuck behind a technical roadblock.
Join Now