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c#entity-frameworkef-code-firstmapping
JesperCodes
JesperCodes

Reputation: 294

EF code-first mapping confusions

I am currently working with Entity Framework Fluent API doing code-first approach mapping configurations, as I run into some confusing scenarios.

My models and mapping configurations

I have two classes: Organisation and Course.

public class Organisation {
    public int Id { get; set; }
    public virtual ICollection<Course> Courses { get; set; }
}

public class Course {
    public int Id { get; set; }
    public int OrganisationId { get; set; }
}

My mapping configurations look like:

public class OrganisationSchema : EntityTypeConfiguration<Organisation>
{
    public OrganisationSchema()
    {
        ToTable(typeof(Organisation).Name);
        HasKey(x => x.Id);
        HasMany(x => x.Courses).WithRequired(x => x.Organisation).HasForeignKey(x => x.OrganisationId);
    }
}

public class CourseSchema : EntityTypeConfiguration<Course>
{
    public CourseSchema()
    {
        ToTable(typeof(Course).Name);
        HasKey(x => x.Id);
        HasRequired(x => x.Organisation).WithMany(x => x.Courses).HasForeignKey(x => x.OrganisationId);
    }
}

My goal

My goal with my models is to have an Organisation with many Courses, while Course has only one Organisation.

Additionally if I delete an Organisation, I want EF to delete all Courses related. But if I delete a Course, one should not delete any Organisations.

Questions

  1. Right now, in my mapping configurations, I explicit tell that one Organisation has many Courses and point out the foreign keys. And then I tell the exact same on one Course, just the other way around. Is this both-way mappings really nescessary, or could I skip one of the sides? How little mapping configuration is needed for EF to understand my goal? I really don't want to blow my code, neither my head.

  2. According to my goal, I need some entity deletion handling. I know that this is configured by using the WillCascadeOnDelete() extension, but I don't understand this extension. Where should I set the WillCascadeOnDelete() extension on my mapping configurations; which of the two sides - or both? How does it affect? And what is the boolean parameter value telling?

Upvotes: 2

Views: 89

Answers (1)

JBA
JBA

Reputation: 220

public class Organisation {
public int Id { get; set; }
public virtual ICollection<Course> Courses { get; set; }
}

public class Course {
    public int Id { get; set; }
    public virtual Organisation Organisation { get; set; }
}



 public class OrganisationSchema : EntityTypeConfiguration<Organisation>
{
    public OrganisationSchema()
    {
        ToTable(typeof(Organisation).Name);            
        HasMany(x => x.Courses).WithRequired(x => .Organisation).WillCascadeOnDelete();
    }
}

I think the above configuration should work for what you are asking. It uses some conventions for defining foreign key and keeps the mapping configuration to a minimum.

Upvotes: 1

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