So I changed up my databases and remade them. I followed the EF6 tutorial but encountered this error when trying to create a controller with views. I did some research on the error and people said to add data annotations and I tried [Key] but I keep getting the same error. Not sure if i've forgotten anything? Thanks!
"There was an error running the selected code generator: 'Unable to retrieve metadata for 'LinkDB.Models.Identifier.' Unable to determine the principal end of an association between the type 'LinkDB.Models.Identifier' and 'LinkDB.Models.Identity'. The principal end of this association must be explicity configured using either the relationship fluent API or data annotation.'
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
namespace LinksDB.Models
{
public class Identity
{
[Key]
public int ID { get; set; }
public int IdentifierID { get; set; }
public string contact { get; set; }
public string contactname { get; set; }
public string price { get; set; }
public virtual ICollection<Link> Links { get; set; }
public virtual Identifier Identifiers { get; set; }
public virtual Metric Metrics { get; set; }
}
}
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
namespace LinksDB.Models
{
public class Identifier
{
[Key]
public int ID { get; set; }
public string domain { get; set; }
public virtual ICollection<Link> Links { get; set; }
public virtual Identity Identitys { get; set; }
public virtual Metric Metrics { get; set; }
}
}
using LinksDB.Models;
using System.Data.Entity;
using System.Data.Entity.ModelConfiguration.Conventions;
namespace LinksDB.DAL
{
public class LinkData : DbContext
{
public LinkData() : base("LinkData")
{
}
public DbSet<Identifier> Identifiers { get; set; }
public DbSet<Identity> Identitys { get; set; }
public DbSet<Link> Links { get; set; }
public DbSet<Metric> Metrics { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
}
}
}
OK, if you want a 1:1 relationship between Identity and Identifier those models should look like below where the child (Indentifier) uses the IdentityId as both it's PK and FK. You can also do this with fluent code. Start with this and then add in your Metric and Links relationships.
public class Identity
{
[Key]
public int ID { get; set; }
public string contact { get; set; }
public string contactname { get; set; }
public string price { get; set; }
public virtual Identifier Identifier { get; set; }
}
public class Identifier
{
[Key, ForeignKey("Identity")]
public int IdentityID { get; set; }
public string domain { get; set; }
public virtual Identity Identity { get; set; }
}
Example here
Related
Hi I have model with to table and a one to many relationship between
Order and status
i want to show a list with all of properties in order and the last Title in status according to Order id in order
how could i get it?
thank you
this is my code :
namespace Pur.Models
{
using System;
using System.Collections.Generic;
public partial class Order
{
public int OrdeId { get; set; }
public Nullable<int> UserID { get; set; }
public Nullable<System.DateTime> OrderDate { get; set; }
public string Description { get; set; }
public int Quantity { get; set; }
public string Unit { get; set; }
public string Priority { get; set; }
public string Department { get; set; }
public virtual ICollection<Status> Status { get; set; }
}
}
and the other:
namespace Pur.Models
{
using System;
using System.Collections.Generic;
public partial class Status
{
public int StatusId { get; set; }
public string Title { get; set; }
public int OrderID { get; set; }
public Nullable<System.DateTime> StatusDate { get; set; }
public virtual Order Order { get; set; }
}
You can create join query and then pass it to a new model
var query = your query
var Lists = db.Database.SqlQuery<OrderModel>(query);
i'm trying create DB using codefirst. i want to create two ForeingKey from same table. But when i set up two navigation properties of the same type, get error like :
The foreign key name 'FollowedUser' was not found on the dependent type Models.UserUserWatchListItem'. The Name value should be a comma separated list of foreign key property names.
public class UserUserWatchListItem
{
public int Id { get; set; }
[Key,ForeignKey("FollowedUser")]
public virtual User FollowedUser { get; set; }
public int FollowedUserId { get; set; }
[Key,ForeignKey("FolloweeUser")]
public int FolloweeUserId { get; set; }
public virtual User FolloweeUser { get; set; }
}
Use this :
public class UserUserWatchListItem
{
public int Id { get; set; }
public int FollowedUserId { get; set; }
public int FolloweeUserId { get; set; }
[ForeignKey("FollowedUser")]
[InverseProperty("FollowedUsers")]
public virtual User FollowedUser { get; set; }
[ForeignKey("FolloweeUser")]
[InverseProperty("FolloweeUsers")]
public virtual User FolloweeUser { get; set; }
}
public class User
{
...
[InverseProperty("FollowedUser")]
public virtual ICollection<UserUserWatchListItem> FollowedUsers { get; set; }
[InverseProperty("FolloweeUser")]
public virtual ICollection<UserUserWatchListItem> FolloweeUsers { get; set; }
}
I want to have a list of stands (at a trade show) and a list of exhibitors.
The list of stands is separate to the list of exhibitors - however, once registered, I want the exhibitor to be able to book a stand.
When they select/book a stand - I would like to then be able to have a list the stands in my view, and also show the associated exhibitor who has booked it.
Likewise, I would like to list in another view, the exhibitors, and also which stand they have booked.
So I'm trying to setup a one to one relationship (using EF CodeFirst).
However, when trying to add a controller for either the Stand or the Exhibitor, I get the following error:
My models are:
public class Stand
{
public int StandID { get; set; }
public string Description { get; set; }
public bool Booked { get; set; }
public int ExhibitorID { get; set; }
public virtual Exhibitor Exhibitor { get; set; }
}
public class Exhibitor
{
public int ExhibitorID { get; set; }
public string Company { get; set; }
public int StandID { get; set; }
public virtual Stand Stand { get; set; }
}
I'm certain it's something to do with the "Virtual" part of the models.
Can anyone please help point out what should be updated, to allow the connection?
Thank you,
Mark
EF doesn't know which entity is the principal (parent) and which is the dependent (child). You need to declare a foreign key on the item that entity that should come first. You can do this with an annotation or a fluent mapping.
Annotation
Add the following namespace:
using System.ComponentModel.DataAnnotations.Schema;
Annotate your Stand class with the following annotation:
public class Stand
{
[ForeignKey("Exhibitor")]
public int StandID { get; set; }
public string Description { get; set; }
public bool Booked { get; set; }
public int ExhibitorID { get; set; }
public virtual Exhibitor Exhibitor { get; set; }
}
Fluent Mapping
Override your OnModelCreating method in your DbContext class to include:
modelBuilder.Entity<Stand>()
.HasOptional(s => s.Exhibitor)
.WithRequired(e => e.Stand);
The model you have created is not possible to work with relational databases. The Stand needs an ExibitorId while Exibitor need a StandId. The cyclic relationship does not allow you to insert any rows to either tables.
Assuming an Exibitor may have more than one Stand and converting the relationship to one-to-many is one option.
public class Stand
{
public int StandID { get; set; }
public string Description { get; set; }
public bool Booked { get; set; }
public int? ExhibitorID { get; set; }
public virtual Exhibitor Exhibitor { get; set; }
}
public class Exhibitor
{
public int ExhibitorID { get; set; }
public string Company { get; set; }
public virtual ICollection<Stand> Stands { get; set; }
}
Or you can use shared primary key mapping to make the relationship one-to-one. Where Stand is the principal entity. The Exibitor will use the StandID as its PK.
public class Stand
{
public int StandID { get; set; }
public string Description { get; set; }
public bool Booked { get; set; }
public virtual Exhibitor Exhibitor { get; set; }
}
public class Exhibitor
{
public int ExhibitorID { get; set; }
public string Company { get; set; }
public virtual Stand Stand { get; set; }
}
Using the Fluent API to configure the relationship.
modelBuilder.Entity<Exibitor>().HasRequired(e => e.Stand)
.WithOptional(s => s.Exibitor);
I have the following model:
public class Member
{
public int Id { get; set; }
public string Username { get; set; }
public int MainEmailId { get; set; }
public virtual Email MainEmail { get; set; }
public virtual ICollection<Email> MemberEmails { get; set; }
}
public partial class Email
{
public Int32 Id { get; set; }
public String Email { get; set; }
public int MemberId { get; set; }
public virtual Member Member { get; set; }
}
As you can see I wish to create a:
one-to-one relation from the Member to MemberEmail (the main email address)
one-to-many relation from Member to MemberEmail
I know how to do this with Code First Fluent API. However I need to do it with DataAnnotations only. Is this possible?
Thanks a lot.
I have this class.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
namespace TestConnect
{
public class UserInfo
{
public string id { get; set; }
public string name { get; set; }
public string picture { get; set; }
public string bio { get; set; }
public string quotes { get; set; }
//public HometownInfo from { get; set;
public From hometown { get; set; }
public string relationship { get; set; }
public string gender { get; set; }
public List<Education> data { get; set; }
}
public class Education
{
public From school { get; set; }
public From year { get; set; }
//public From [] concentration { get; set; }
public string type { get; set; }
}
}
public class HometownInfo
{
public string id { get; set; }
public string homename { get; set; }
}
Now trying to do
url = "https://graph.facebook.com/me?fields=education&access_token=" + oAuth.Token;
json = oAuth.WebRequest(oAuthFacebook.Method.GET, url, String.Empty);
Education edu = js.Deserialize<Education>(json);
foreach(Education_history edu_history in Education.data) gives an error
Object reference not set to an
instance of an object. Description: An
unhandled exception occurred during
the execution of the current web
request
Thanks
User
Have you tried setting breakpoints at the various steps in your code and seeing where it might be?
somewhere else in your code you must be declaring url and json?
does js.Deserialize() create a new object or are you missing this
Education edu = new Education();
Also if its in a web application make sure that your code is placed in the correct page events so that they happen in the correct order