Can't insert data to with EF with Master-detai

问题:

Suppose I have 2 tables:

Person(pid, ....)   //Pid is identify colum as primary key
Student(pid, Student_No,...)   //pid is foreign key from Person, pid is a primary key too.

Then use EF to generate entity model. THen try to insert new data with following code:

 Person person = new Person()
           { FirstName = "FirstName", LastName= "LastName", ... };
 Student student = new Student(){Student_No="001", ...};
 Student.Person = person;
 mycontext.Students.AddObject(student);
 mycontext.SaveChanges();

Then I get error as: A dependent property in a ReferentialConstraint is mapped to a store-generated column. Column: 'pid'.

How to fix it?

Modify the code like:

 Person person = new Person(){ FirstName = "FirstName", LastName= "LastName", ... };
  mycontext.People.AddObject(person);
  mycontext.SaveChanges();

 Student student = new Student(){Student_No="001", Person = person,  ...};
 // or  Student student = new Student(){Student_No="001", pid= person.pid,  ...};
 mycontext.Students.AddObject(student);
 mycontext.SaveChanges();

then I was able to insert for person, but for Student, still get same error. Check Student entity pid property in EDM: storegeneratedPatteren = None. Quite confused.

回答1:

Sounds like you have a student which is a type of person. If this is true then you should consider using Table-per-type Inheritance. Details here http://msdn.microsoft.com/en-us/library/bb738685.aspx

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Edited:

If you choose not to use inheritance you need to insert the person first:

 Person person = new Person()
           { FirstName = "FirstName", LastName= "LastName", ... };

 mycontext.Person.AddObject(person);
 mycontext.SaveChanges();

回答2:

Check Student entity pid property in EDM: storegeneratedPatteren = None. Quite confused.

Still has to do with the identity specification (is identity, identity increment, identity seed) for the table you are adding to, or the table column a relationship was mapped to. The error 'A dependent property in a ReferentialConstraint is mapped to a store-generated column' shows if:

1. You pass a new object to addObject() with a field for which a value was set that should be generated by the database. Solution: Do not pass a value for fields that have an autoincrement id in the database.

2. You accidentally mapped the primary key of a table to a wrong foreign column in your database. Solution: Review the foreign key relationship.

The second case is less obvious, but it happens often if you quickly drag and drop constraints in a diagram.