EF Code First with One-to-Many and Many-to-Many relationships? cause cycles or multiple cascade paths - ef-code-first

Question

I have four models that are Family, Mother, Father, Student, I am trying to associate Father& Mother& Student with Family table and Student table associated with Mother and Father tables. Here Family table contains information about the family. Mother and Father Tables contain their personal information, and Student table contains student information + MotherID and FatherID. Which means Family table was the Primary table to Mother and Father, Student table. MotherID of Mother table and FatherID of father table were referenced to Student table.
I am using MVC 4 Entity Framework Code First,
These are my model classes.
public class Family
{
public int FamilyID { get; set; }
public string FamilyName { get; set; }
public virtual ICollection<Mother> Mothers { get; set; }
public virtual ICollection<Father> Fathers { get; set; }
public virtual ICollection<Student> Students { get; set; }
}
public class Mother
{
public int MotherID { get; set; }
public int FamilyID { get; set; }
public string FirstName { get; set; }
public string SSN { get; set; }
public virtual Family Families { get; set; }
public virtual ICollection<Student> Students{ get; set; }
}
public class Father
{
public int FatherID { get; set; }
public int FamilyID { get; set; }
public string FirstName { get; set; }
public string SSN { get; set; }
public virtual Family Families { get; set; }
public virtual ICollection<Student> Students { get; set; }
}
public class Student
{
public int StudentID { get; set; }
public int FamilyID { get; set; }
public int MotherID { get; set; }
public int FatherID { get; set; }
public string FirstName { get; set; }
public string SSN { get; set; }
public virtual Family Families { get; set; }
public virtual Mother Mothers { get; set; }
public virtual Father Fathers { get; set; }
}
Database Context Class:
public class MYContext:DbContext
{
public DbSet<Family> Families { get; set; }
public DbSet<Mother> Mothers { get; set; }
public DbSet<Father> Fathers { get; set; }
public DbSet<Student> Students { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
//modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
//base.OnModelCreating(modelBuilder);
}
}
After writing the above code I just ran the below commands on package manager console.
PM> Add-Migration InitialContext It created an InitialContext.cs class for me.
PM> Update-Database -Verbose It give me an error below
Introducing FOREIGN KEY constraint 'FK_dbo.Student_dbo.Mother_MotherID' on table
'Student' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON
UPDATE NO ACTION, or modify other FOREIGN KEY constraints.
Could not create constraint. See previous errors.
What am I doing wrong??
Why I am getting this error??? Please help me some one!
What is the correct way to implement one-to-many and many-to-many relationships using EF code first? Please guide me with this example.

Answer 1

Try adding the [key] annotation immediately above your keys. For instance, for the student, it would look like this...
public class Student
{
[key]
public int StudentID { get; set; }
public int FamilyID { get; set; }
public int MotherID { get; set; }
public int FatherID { get; set; }
public string FirstName { get; set; }
public string SSN { get; set; }
public virtual Family Families { get; set; }
public virtual Mother Mothers { get; set; }
public virtual Father Fathers { get; set; }
}
This will tell you, in detail, how to manage your model from a codefirst perspective.
http://thedatafarm.com/blog/data-access/code-first-entity-framework-4-1-videos-and-articles-on-msdn/

Answer 2

I have found same problem and solution at Entity Framework, Code First modeling and a cyclical reference
The exception was coming from SQL Server DB not from entity framework, that table structure with the same constraints created by hand will be invalid. Foreign key properties of Mother table (Mother.FamilyID) and Father Table (Father.FamilyID), Student table (Student.MotherID) & (Student.FatherID) are not nullable, those representing required relationships and the corresponding columns in the database are also not nullable. So DB is not allowing this model.
If I remove all these properties from model classes then automatically relationship become optional because the navigation properties can be null, So DB treated as this is another model now since the FK columns in the DB can be nullable. Seemingly this is an allowed model.
It worked for me! Use nullable types as follows
Here is the solution for cause cycles or multiple cascade paths issues:
public class Student
{
public int StudentID { get; set; }
public int FamilyID { get; set; }
public int? MotherID { get; set; } //nullable types
public int? FatherID { get; set; } //nullable types
public string FirstName { get; set; }
public string SSN { get; set; }
public virtual Family Families { get; set; }
public virtual Mother Mothers { get; set; }
public virtual Father Fathers { get; set; }
}
Finally my model becomes with foreign key properties which represent optional instead of required relationship.
really very very thanks to # https://stackoverflow.com/users/270591/slauma and
https://stackoverflow.com/users/173937/decibyte for helping me in this type issue.