I am using Visual Studio 2012 and i have created a .sdf and .edmx for my database.
I was wondering what would be the best way to set the relationships between the entities.
I have tried just setting the association with the multiplicity set and get an error saying that they are not mapped.
Also how do you set the foreign keys.
I am trying to create a estate agent like system to book appointments online and in branch. I am creating it in C#.
I Assume you are going Database first.
If so, if you just simply creat your foreign keys and constraints in your database and then try to add your entities again, then your edmx file will have the relationships and everything.
Related
I am working on a project where I may not alter the database in any way (unfortunately). I have started the project using Entity Framework and this has worked for the first few objects that I need. Now I have come across two scenarios that I am not sure how to accommodate.
Tables without a primary key defined.
Tables using the suffix of the table name as a field.
For the first, I get an error about reviewing my schema and uncommenting the proper area of the edmx file. The table has a field that acts as primary key but is not designated as not null and does not have a primary key created for it.
For the second, there are several tables with names like order1, order2, order3 etc where the table that needs to be accessed would be a parameter of my access methods.
My thought is that it would be simplest to just manually write the SQL and bind the data to models. If I go that route would I even use EF or do I just create a new database connection? what would be the 'proper' way to go about that?
Am very new to Entity Framework. I am using vs 2012 professional 2012 for building my mvc4 app.
I will try to explain problem in my limited knowledge
I have created Ado.net entity data model. After that I have chnaged db for setting relations. After "update model from database" the relations are not gettng added to model classes. So when I run my app errors like
The relationship 'x.FK_Privileges_Module' was not loaded because the type 'x.Privilege' is not available.
is shown
How can I solve this. I even tried adding manually the relation to corresponding . cs file and still getting error for every newly added relation.
How can I solve this?
You can remove entities from model designer (Press Yes when message box will ask) and then add entities again.
Note: To delete, select entities and press delete key
The edmx is not able to find a Primary Key on Privilege and therefore the foregin key is not valid.
Add a Primary Key on Privilege
I am working on a custom ado.net provider and using that provider I am integrating Entity Framework support in Visual Studio 2010. I'm creating all possible mapping and reading all the related metadata from database for table objects. For my test, a table contains primary keys and and other fields. When I create a model from database using this table and I get a model with all column mappings and everything but I also get error messages that follow:
The model was generated with warnings or errors.
Please see the Error List for more details. These issues must be fixed before running your application.
Loading metadata from the database took 00:00:11.4799371.
Generating the model took 00:00:04.2751189.
Added the connection string to the App.Config file.
Writing the .edmx file took 00:00:00.0005060.
If I open the .edmx file with XML editor, I see the following error:
<!--Errors Found During Generation:
warning 6002: The table/view 'sqlfire.APP.CUSTOMERS' does not have a primary key defined. The key has been inferred and the definition was created as a read-only table/view.
-->
It also added a DefiningQuery with a SELECT ... statement for the table.
I am going in a circle to find a solution and desperately looking for some help on this issue.
From the error message looks like one of your table/view doesn't have a Primary-Key. EF needs a Primary-Key in every table in order to generate Entity keys.
You may still be able to run your application, but I strongly suggest you add primary keys as warned.
I generate Entity Data Model in Visual studio from the database.
However, I noticed that it does not generate neither relationships nor navigation properties from some foreign keys. It occurs when the foreign key contsraints are defined with the disabled option Enforce Foreign Key Constraint, like in the following exhibit (from SSMS).
Is there any way to deal with this? Unfortunately I cannot alter my database schema.
You can add them manually from the designer but it can have some consequences depending on the version of entity framework yo are using.
If you simply add association from the toolbox it by default creates independent association. Independent association must be mapped to the database counterpart. It means that you must manually open EDMX and cheat EF by modifying SSDL (you will add relation to SSDL part manually which can be quite hard task - follow SSDL reference: AssociationSet and Association elements). Now you can map the relation in the Mapping details window of the designer (you will also have to modify entities because FK property mustn't be mapped to the entity when independent association is used and in case of many-to-many association you will have to remove entity for junction table). EF will believe that this relation exists in the database. Once you modify SSDL manually you cannot use Update from the database any more. It will delete all your manual changes.
If you are using EFv4 you can use foreign key association (complete differences between those two types is described here). Foreign key association is not mapped but it cannot be used to define many-to-many relation.
The problem will occur if data in the database doesn't enforce the relation (which can happen because FKs are disabled). In such case your application will not work and there will be no way around this except repairing data integrity in the database or removing the association from the model.
The best solution for you is turning on FKs in the database!
Unfortunately You have to add those by hand in the model. That's the power of OR Mapping. Model can look different (better) than database.
I am using EF 4.0 and am generating my Entity Model (.edmx) file from my database. I have several foreign key constraints for Cascade OnDelete, however, these are not getting set on my associations in my entity model. I click on the association and it shows End1 OnDelete: None.
When I check the Delete rules in my SQL Server 2008 database on my foreign key constraint, it says 'Cascade'.
Is there something I am missing to get the Cascade OnDelete flag to set in my entity model?
This answer
"I was having the same problem with SQL Server. When I tried to update mode from database, it didn't pick up the cascade rules. Note that the rules were added after the model was already created. I even tried deleting a table from the model and adding it back in. That had the same effect - no cascade rules.
However, when I created a brand new model with the same exact tables, it picked up the cascade rules. So my solution was just to delete the old model and create a new one with the same name, etc.
I guess is that there is something wrong with the update model from database process."
from this thread worked for me.