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Entity Framework: determine sides of foreign key relation


Entity Framework: determine sides of foreign key relation

By : Rana Dheeran
Date : November 21 2020, 11:01 PM
I hope this helps . The Entity Framework Mapping Api is one way to do it. I think it is technically possible to do what you need directly against EF but the code is a nightmare. I recall just trying to look up the primary keys directly against EF and it was convoluted. This library will make you life a lot easier.
The only one thing it does not do is show you the child relations, just the Foregin Keys. So you will need to implement your own logic to get child relations.
code :


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Asp.net MVC 2 relation without Foreign Key with Entity Framework 4 Or With Foreign Key

Asp.net MVC 2 relation without Foreign Key with Entity Framework 4 Or With Foreign Key


By : user2293302
Date : March 29 2020, 07:55 AM
wish help you to fix your issue 1 - Is it necessary to have foreign key to obtain a Relation in Entity Framework between each entity.? , You can always get the Language info by using the Linq queries like:
code :
YourContainer db = new YourContainer();

var Text = from m in db.TableTextASet
           join n in db.LanguageSet on n.LangID equals m.LangID
           select new
           {
               Id = m.TblAID,
               Text = m.TextInfo,
               Language = n.LangName
           };
Entity Framework - Get count of foreign-key relation

Entity Framework - Get count of foreign-key relation


By : Crystalline
Date : March 29 2020, 07:55 AM
like below fixes the issue I have a simple categories management system. , Try
code :
if ( category.Members.CreateSourceQuery().Count() > 0 )
Error using entity framework to add rows to tables using foreign key relation

Error using entity framework to add rows to tables using foreign key relation


By : oo12
Date : March 29 2020, 07:55 AM
wish help you to fix your issue Your EntitySet "'UCV_TF_Assignments_New" is either based on a View (in which case, you have to create the InsertFunction (stored procedure)) or it lacks a Primary Key (in which case, add one).
How to let a bidirectional relation not create foreign keys on both sides when adding another relation?

How to let a bidirectional relation not create foreign keys on both sides when adding another relation?


By : user3689211
Date : March 29 2020, 07:55 AM
This might help you If you look under "Relationship Convention" on Code First Conventions, it says
code :
public class Sector
{
    public Int64 X { get; set; }
    public Int64 Y { get; set; }

    [InverseProperty("Sector")] 
    public virtual ICollection<Ship> Ships { get; set; }
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    // other stuff...
    modelBuilder.Entity<Ship>()
        .HasRequired(p => p.Sector)
        .WithMany(p => p.Ships);

    modelBuilder.Entity<Ship>()
        .HasRequired(p => p.Destination)
        .WithMany()
        .WillCascadeOnDelete();
}
Entity Framework Foreign Key For Circular Relation

Entity Framework Foreign Key For Circular Relation


By : Ajay
Date : March 29 2020, 07:55 AM
I wish this helpful for you It's possible, but since this design creates circular dependency between the two entities, it would cause you a lot of problems. For instance, not only one of the relationships (let say from CrtChk to Crt) cannot use cascade delete, but also you cannot simply delete the Crt without first updating the ActiveCrtChkId to null (and calling SaveChanges).
Anyway, here is how you configure the desired relationships. Usually it would be enough to use InverseProperty attribute to resolve navigation property mapping ambiguity, but one-to-one unidirectional (i.e. with navigation property only at one of the ends) requires fluent configuration (otherwise it will be mapped by convention to one-to-many). Also specially for relationships, I find explicit fluent configuration much clear than considering all EF conventional assumptions and data annotations like where to put ForeignKey attribute (on FK property or navigation property), what string to put there is the first or later case etc.
code :
// Crt 1 - 0..N CrtChk
modelBuilder.Entity<Crt>()
    .HasMany(e => e.CartChecks)
    .WithOne(e => e.Cart)
    .HasForeignKey(e => e.CrtId)
    .OnDelete(DeleteBehavior.Cascade);

// CrtChk 1 - 0..1 Crt
modelBuilder.Entity<Crt>()
    .HasOne(e => e.ActiveCrtChk)
    .WithOne()
    .HasForeignKey<Crt>(e => e.ActiveCrtChkId)
    .OnDelete(DeleteBehavior.Restrict);
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