Models:
public class Status
{
public int Id { get; set; }
}
public class Podcast
{
public int Id { get; set; }
public virtual Status Status { get; set; }
}
The Podcast table has the StatusId column, and this column is a foreign key. In this case I've got the following error message: Invalid column name 'Status_Id'. Why? - Many times I faced that articles with such examples. This is the first question.
Ok, no problem - i've added an underscore character to these columns: Sttaus_Id and so on.
Now it seems that everything works fine, but when I modify my model by the following way:
public class Podcast
{
public int Id { get; set; }
public int Status_Id { get; set; }
public virtual Status Status { get; set; }
}
Now I get the following error: Invalid column name 'Status_Id1'.
Why? I can't use the DropDownListFor helper without these xx_id properies.
I believe the issue here is that you have created your DB first and created a column named StatusId for your FK reference but you haven't told EF that you are using a non-default column name for your FK.
the following will give you the structure you are after (ps i agree with your naming convention i personally dislike the _ in fk ids)
public class MyContext : DbContext
{
public DbSet<Podcast> Podcasts { get; set; }
public DbSet<Status> Status { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Podcast>().HasOptional(p => p.Status)
.WithMany().HasForeignKey(p => p.StatusId);
base.OnModelCreating(modelBuilder);
}
}
public class Status
{
public int Id { get; set; }
}
public class Podcast
{
public int Id { get; set; }
public int? StatusId { get; set; }
public virtual Status Status { get; set; }
}
The convention at least for the foreign key field is table name + field name, so in your case StatusId without the underscore. But I'm not sure why it says invalid column name Status_Id1.
Remove the underscore, and try again. If you still get an error message, please make an edit to your question with the results.
Related
I'm getting the following error when I try to insert a new row in one of my relational tables. I have the following two models:
public class CompanyCredit
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int creditId { get; set; }
public int planCredit { get; set; }
public DateTime? PlanCreditExpirationDate { get; set; }
}
And
public class CompanyInformation
{
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int id { get; set; }
[Required]
[DisplayName("Company Name:")]
public string companyName { get; set; }
public string timeZone { get; set; }
//navigation Properties
public virtual CompanyCredit Credits { get; set; }
}
And this Relation in the dbContext
modelBuilder.Entity<CompanyInformation>().HasOptional(e => e.Credits);
I'm trying to add a record inside CompanyCredit table like so:
if (_company.Credits == null)
{
var _credits = new CompanyCredit();
_credits.planCredit = 200;
_credits.PlanCreditExpirationDate = System.DateTime.UtcNow.AddMonths(1);
_company.Credits = _credits;
repo.InsertOrUpdate(_company, User.Identity.Name);
}
And Finally Insert or update just marks Company as changed and _credit as added like so:
_db.Entry(_credits).State = System.Data.EntityState.Added;
_db.Entry(Company).State = System.Data.EntityState.Modified;
_db.SaveChanges();
When this runs I get the following Error that I just can't seem to find the reason to.
Cannot insert the value NULL into column 'creditId', table 'Project.dbo.CompanyCredits'; column does not allow nulls. INSERT fails.
The statement has been terminated.
Thank in advanced for your help.
I found the problem was in the attribute [DatabaseGenerated(DatabaseGeneratedOption.Identity)] this should have been [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
I thought I would post this so others might benefit from it.
Could you please try reversing the order of entity state modification, just before the saveChanges call
_db.Entry(Company).State = System.Data.EntityState.Modified;
_db.Entry(_credits).State = System.Data.EntityState.Added;
_db.SaveChanges();
Note: Technoligies in use are ASP.Net MVC 3, Entity, SQL Server Management Studio
Problem?
It seems that when I run, the context as: public class DatabaseInit : DropCreateDatabaseAlways<LocationAppContext>
That it creates the database, but my service assignments table has an extra foreign key called
ServiceAssignment_Service when it shouldn't.
My service assignment model is as such:
namespace LocationApp.Models
{
public class ServiceAssignment
{
public int id { get; set; }
public int locationID { get; set; }
public int ServiceID { get; set; }
public virtual Location Location { get; set; }
public virtual ServiceAssignment Service { get; set;}
}
}
and the service model is as such:
namespace LocationApp.Models
{
public class Service
{
public Service()
{
this.ServiceAssignments = new HashSet<ServiceAssignment>();
}
public int id { get; set; }
public string name { get; set; }
public string description { get; set; }
public bool active { get; set; }
public string icon { get; set; }
public virtual ICollection<ServiceAssignment> ServiceAssignments { get; set; }
}
}
with that said, the relation ship is simple:
service assignments have many location id's and service id's.
why is this extra foriegn key being generated? the curent keys, that should e there is:
PK: Main PK for the table
FK 1: Location_ServiceAssignment
FK 2: Service_ServiceAssignment
Those are their, how ever this third one is baffling....
The second part is: If a location of id 2 has a service id of 2,3,6,7 How do I get all service id's returned, such that I can pass the object to a service query to get all information on the service based on the ID?
Update:
Context Class:
namespace LocationApp.DAL
{
public class LocationAppContext : DbContext
{
public DbSet<Content> Contents { get; set; }
public DbSet<Location> Locations { get; set; }
public DbSet<ServiceAssignment> ServiceAssignments { get; set; }
public DbSet<Service> Services { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
modelBuilder.Entity<Location>().HasMany(sa => sa.ServiceAssignments);
modelBuilder.Entity<Service>().HasMany(sa => sa.ServiceAssignments);
}
}
}
I think you have to tell EF that Service.ServiceAssignments is the inverse navigation property of ServiceAssignment.Service and that Location.ServiceAssignments is the inverse of ServiceAssignment.Location. Right now with your mapping you only specify that Location or Service has many ServiceAssignments. EF will consider the navigation properties in ServiceAssignment as the ends of separate relationships.
Try instead the mapping:
modelBuilder.Entity<Location>()
.HasMany(l => l.ServiceAssignments)
.WithRequired(sa => sa.Location)
.HasForeignKey(sa => sa.LocationID);
modelBuilder.Entity<Service>()
.HasMany(s => s.ServiceAssignments)
.WithRequired(sa => sa.Service)
.HasForeignKey(sa => sa.ServiceID);
You can probably remove this mapping altogether as an alternative because EF should detect the right relationships by convention.
So, use either no mapping (=mapping by convention) or the full mapping (=specifying both ends of the relationships). Just the 50%-mapping you have used is likely the problem.
Models:
public class User
{
[Key]
public int UserId { get; set; }
public string UserName { get; set; }
}
public class Resource
{
[Key]
public int ResourceId { get; set; }
public string ResourceName { get; set; }
public string ResourceDescription { get; set; }
}
public class UserResource
{
[Key, Column(Order=0)]
public int UserId { get; set; }
[Key, Column(Order=1)]
public int ResourceId { get; set; }
public int ResourceQuantity { get; set; }
}
I want to select "ResourceName" from Resource model and "ResourceQuantity" from UserResource model for a given "UserId". Also, once selected, do I need a brand new model to carry only those two specified columns?
Also note that UserResource model has a composite key so I am confused as to how to make the join... Is this right?
var userResources =
from r in imDB.Resources
join ur in imDB.UserResources
on r.ResourceId equals ur.ResourceId
select new { r.ResourceName, ur.ResourceQuantity };
Hence you're using Code first you can create your models are as below by using EF conventions.
public class User {
public int Id { get; set; }
public string UserName { get; set; }
public virtual ICollection<Resource> Resources { get; set; }
}
public class Resource {
public int Id { get; set; }
public string ResourceName { get; set; }
public int ResourceQuantity { get; set; }
public virtual ICollection<User> Users {get;set;}
}
Then EF will generate your junction table is as UsersResources.You don't need to create additional model as you did.EF will look after that.
When using POCOs with EF, if you mark your navigation properties as
virtual you can use additional EF supports like Lazy Loading. So in
general use a virtual keyword in navigation properties considered to
be a good practice.
UPDATE
You may try something like below:
Method 1 : Method based syntax
imDB.Resources.Where(r => r.Users.Any(u => u.UserId == userId))
Method 2 : Query based syntax
from r in imDB.Resources
from u in r.Users
where u.UserId == userId
select r;
I hope this will help to you.
I have something like this: (pseudocode)
public class Author
{
int id;
public List<Thread> Threads;
public List<ThreadPoints> ThreadPointses;
}
public class Thread
{
int id;
public List<ThreadPoints> ThreadPointses;
}
public class ThreadPoints
{
int id;
int Points;
}
And i am not sure if above is correct, but now i would want to obtain number of points' that specified Author have in specified Thread.
I cannot directly call ThreadPoints.Thread_id, because it's not accessible, even if it physically is in the database.
So do i need to change my model, or am i unaware of some useful methods?
So basically, my model looks like that:
public class Account
{
[Key]
public Guid AccountId { get; set; }
public string UserName { get; set; }
public List<Post> Posts { get; set; }
public List<Post> ModifiedPosts { get; set; }
public List<Thread> Threads { get; set; }
public List<ThreadPoints> ThreadPointses { get; set; }
public List<Thread> LastReplied { get; set; }
public int Points { get; set; }
}
public class Thread
{
[Key]
public int Id { get; set; }
public List<ThreadPoints> ThreadPointses { get; set; }
public List<Post> Posts { get; set; }
public int CurrentValue { get; set; }
public int NumberOfPosts { get; set; }
public int TotalValue { get; set; }
public int Views { get; set; }
public string Title { get; set; }
public DateTime DateCreated { get; set; }
}
public class ThreadPoints
{
[Key]
public int Id { get; set; }
public int Points { get; set; }
}
And what i need, is, when user creates a thread, he gives some amount of points into it. In the next action, i want to take that amount of points (from database), and increase it. But i only have thread id as input information.
Your answer might be good, (as far i am trying to implement it), but anyways, i am not sure about this model. Maybe i should manually add foreign keys into my model? It surely would be simpler, but then i would have two foreign keys in my database...
Since you're not explicitly mapping your FK's, entity framework is generating them and hiding them away, so to get to the Id's of the properties, you'll need to follow the navigation collections.
I'm not sure about your question, but are you wanting the number of Points, inside of a specific Threadpoint for a given author? Your model doesn't seem to support this very well, but you could do something like this-
public int GetPoints(Author author, Thread thread)
{
int points = author.Threads.FirstOrDefault(t => t.id == thread.id).ThreadPointses.Sum(tp => tp.Points);
}
This would return the sum of all the points contained in the list of threadpoints, which are contained in the list of threads with the same id as the thread you passed in, for the specified author.
If this doesn't work for you - can you post your actual model?
I'm trying to find out how I can re-use a simple 'Comment' entity type for multiple scenarios where something is 'commentable' in my application.
At the moment, I have a couple of entities that a user is able to post comments to. Examples include Blogs, Profiles and Photos - these can all be 'commented' on.
I'd like to be able to use the same 'Comment' class for each of these scenarios, but I don't want to end up with one HUGE table full of comments for everything. I figure it would be much more efficient to at least store a table of BlogComments, PhotoComments, and ProfileComments. At the moment, my Comment class looks like this:
public class Comment
{
[Key]
public int Id { get; set; }
public int ContextId { get; set; }
[StringLength(256)]
public string Content { get; set; }
public DateTime DatePosted { get; set; }
public virtual Member Author { get; set; }
}
Presumably, I'd need the 'ContextId' field to refer to the particular thing being commented on. This Id might be the Id of a Blog, a Profile or a Photo. I was hoping to be able to refer to comments much like a normal ICollection in these classes, and I have some code like this for the Photos as an example:
public class Photo
{
[Key]
public int Id { get; set; }
[StringLength(48)]
public string FileName { get; set; }
public virtual Member Owner { get; set; }
public virtual ICollection<Comment> Comments { get; set; }
}
I've been pointed to various articles during my searches, but none really seem relevant to my particular situation. How can I map these comment collections to different tables, and avoid having a comment "super-table"?
Any help, pointers or advice would be hugely appreciated :)
You can create an abstract Comment class and inherit from it specific comments such as PhotoComment, ProfileComment. You will be able to map the comments to different tables.
public abstract class Comment
{
[Key]
public int Id { get; set; }
[StringLength(256)]
public string Content { get; set; }
public DateTime DatePosted { get; set; }
public virtual Member Author { get; set; }
}
public class PhotoComment : Comment
{
public int PhotoId { get; set; }
public virtual Photo Photo { get; set; }
}
public class Photo
{
[Key]
public int Id { get; set; }
[StringLength(48)]
public string FileName { get; set; }
public virtual Member Owner { get; set; }
public virtual ICollection<PhotoComment> Comments { get; set; }
}