First of all ASP.NET and MVC 4 are very new to me (+- one month) and sorry if its a bad question.
I've got two classes "Turma" and "Curso"
public class Turma
{
[Key]
public int idCurso { get; set; }
public string RefTurma { get; set; }
public Curso Curso { get; set; }
public string NomeCurso { get; set; }
}
and
public class Curso
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int idArtigoAT { get; set; }
public string ConteudoPrograma { get; set; }
public virtual ICollection<Turma> Turmas { get; set; }
}
After this I started a migration and updated the database. So far so good, but then problems.
Due to new information the primary key type should be varchar(18). I've tried to change but so far without success.
Any ideia or solution???
No, what you want is an 'Id' property and an 'MyCustomUniqueName' property. this custom property, should be and unique index in database. this is the best design for this situation IMHO.
Related
I am working ASP.NET MVC using Entity frame work code first approach. I am facing an issue ,the issue is as i have dropped two tables by using Package Manager Console.
Now i am trying to add the tables, the tables are not getting added using Package Manager Console.
Getting Error Cannot find the object "dbo.Movies" because it does not exist or you do not have permissions.
Even in Indentity.cs Model [Movies] is mentioned.
public DbSet Movies { get; set; }
Below are the Model.
public class Movie
{
public int Id { get; set; }
public string Name { get; set; }
public DateTime ReleaseDate { get; set; }
public Genre Genres { get; set; }
public byte GenreId { get; set; }
public DateTime DateAdded { get; set; }
public int NumberOfStocks { get; set; }
}
public class Genre
{
public byte Id { get; set; }
public string Type { get; set; }
}
How to the add the new table in existing Entity frame work using Code first approach.
I'm struggling to understand the best way to implement some database relationships in EF Core.
Specifically, it involves the navigation properties, where you make a collection in the parent and an object in the child.
Looking at the MS docs here
Relationships, navigation properties, and foreign keys
there is the typical use case presented of a parent child relationship
public class Course
{
public int CourseID { get; set; }
public string Title { get; set; }
public int Credits { get; set; }
public int DepartmentID { get; set; }
public virtual Department Department { get; set; }
}
public class Department
{
public Department()
{
this.Courses = new HashSet<Course>();
}
public int DepartmentID { get; set; }
public string Name { get; set; }
public decimal Budget { get; set; }
public DateTime StartDate { get; set; }
public virtual ICollection<Course> Courses { get; set; }
}
Now this is fine for the above use case.
However, I am working on a specification system for process recipes. There are lots of machines, materials, areas, buildings and other things involved.
One of the tables in the database is "Unit", as in unit of measurement - that is kg, m, cm, etc.
This table is used as a lookup in many tables in the database, at least 20.
As such, if I've understood the recommended approach, I would end up with
pubic class Unit
{
public Guid Id { get; set; }
public string Name { get; set; }
public virtual ICollection<Recipes> Recipes{ get; set; }
public virtual ICollection<Coll2> Coll2{ get; set; }
public virtual ICollection<Coll3> Coll2{ get; set; }
public virtual ICollection<Coll4> Coll2{ get; set; }
public virtual ICollection<Coll5> Coll2{ get; set; }
public virtual ICollection<Coll..n> Coll..n{ get; set; }
}
This applies not just for unit, but also for quite a few other generic lookup items, such as a warehouse. There are many entities that use a link to the warehouse.
What is the correct approach when using this kind of lookup?
I'm sorry if things aren't clear, hopefully they are.
I'm quite new to .net and entity framework (this is my first project) and I'm getting the following error when trying to update the database:
*Introducing FOREIGN KEY constraint 'FK_Rating_User_UserId' on table 'Rating' 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 or index. See previous errors.*
I tried doing what it says (at least I think so) by adding the following to my dbContext class:
protected override void OnModelCreating(ModelBuilder modelbuilder)
{
modelbuilder.Entity<Rating>().HasOne(u => u.User).WithMany().OnDelete(DeleteBehavior.Restrict);
modelbuilder.Entity<Rating>().HasOne(g => g.Game).WithMany().OnDelete(DeleteBehavior.Restrict);
}
Not sure have I formulated that method correctly but it did not help (I tried with different DeleteBehavior like SetNull and NoAction)
The thing that really got me confused is that the issue appears even after removing all fields related to other tables from Rating class or even all references between all classes.
My Rating class:
public class Rating
{
public long RatingId { get; set; }
//[Rating]
public virtual Game Game { get; set; } // issue appears even after removing this and User line
//[Rating]
public int Score { get; set; }
public string CommentTitle { get; set; }
public string CommentDescription { get; set; }
//[Rating]
public virtual User User { get; set; }// issue appears even after removing this and Game line
}
User class:
public class User
{
public long UserId { get; set; }
//[Required]
public bool IsModerator { get; set; }
//[Required]
public string Username { get; set; }
//[Required]
public string Email { get; set; }
public string Name { get; set; }
public string Surname { get; set; }
//[Required]
public string Password { get; set; }
//[Required]
public string Salt { get; set; }
public string Description { get; set; }
}
Game class:
public class Game
{
public long GameId { get; set; }
//[Required]
public virtual User User { get; set; }
//[Required]
public string Title { get; set; }
public string Description { get; set; }
//[Required]
public string PricingType { get; set; }
public float MinDonation { get; set; }
public float MaxDonation { get; set; }
//[Required]
public string FileLocation { get; set; }
public float AverageRaiting { get; set; }
public int DownloadCount { get; set; }
}
GameImage class (probably unrelated to the issue just wanted to give a full context)
public class GameImage
{
public long GameImageId { get; set; }
//[Required]
public virtual Game Game { get; set; }
//[Required]
public string Location { get; set; }
//[Required]
public bool IsThumbnail { get; set; }
}
dbContext class:
public class dbContext : DbContext
{
public dbContext(DbContextOptions<dbContext> options) : base(options)
{
}
public DbSet<User> User { get; set; }
public DbSet<Rating> Rating { get; set; }
public DbSet<GameImage> GameImage { get; set; }
public DbSet<Game> Game { get; set; }
}
The issue only appeared after I tried to update the database. The first few migrations and updates were ok, however, then I tried adding [Required] annotation (you can see them commented in the above code) as I noticed that most of the fields were created as nullable in my database - after that the issue starting to occur even after removing the annotations.
In case that matters, I'm using Visual Studio 2019 and SQL Server Express
Does anyone have any idea what may be the cause of this?
Edit:
Image of of my database schema diagram from SSMS
As you can see in the database schema it's visible that there are indeed cycles in the database, however, I cannot get rid of them as Entity Framework's command "Update-Database" does not update the DB and just throws the error mentioned above.
Based on my test, you can try the following steps to solve the problem.
First, please change your dbcontext class into the following code.
public class dbContext : DbContext
{
public dbContext() : base("name=MyContext") { }
public DbSet<User> User { get; set; }
public DbSet<Rating> Rating { get; set; }
public DbSet<GameImage> GameImage { get; set; }
public DbSet<Game> Game { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
}
}
Second, please delete all the tables the database.
Third, please try the following command in your package console.
PM> Update-Database -Force
Finally, you can see the new tables in the databse.
I’m coming from an intermediate C++ background (and to a lesser extent, C#) and wanted to try to build a project in Asp.net MVC 6 with EF 7 – not realizing how completely different it is from simple C# forms. I’ve stumbled through and researched a lot but since I’m a total noob I’m stumped at this point.
I have the following models:
public class Shift
{
public int ShiftId { get; set; }
//other properties
public virtual ICollection<ShiftActivity> ShiftActivity { get; set;}
}
public class ShiftActivity
{
public int ShiftActivityID { get; set; }
public DateTime StartTime { get; set; }
public int ShiftID { get; set; }
public int ActivityID { get; set; }
public int LocationID { get; set; }
public virtual Shift Shift { get; set; }
public virtual Activity Activity { get; set; }
public virtual Location Location { get; set; }
}
public class Activity
{
public int ActivityID { get; set; }
public string ActivityName { get; set; }
public virtual ICollection<ShiftActivity> ShiftActivity { get; set; }
}
public class Location
{
public int LocationID { get; set; }
public string LocationName { get; set; }
public string LocationAddress { get; set; }
public int locationZip { get; set; }
public virtual ICollection<ShiftActivity> ShiftActivity { get; set; }
}
I would like to create a shift and be able to input all the required fields all from one view. For instance, when I create the shift, I need to pick the type of location and activity to add to the ShiftActivity table which is then updated. Eventually I would like to be able to dynamically add additional activities (I’m assuming I’ll need javascript for that), but that’s another issue. I know I need a viewmodel to access all the tables, but I’m unclear as to how the viewmodel should be structured correctly.
Also, can the ShiftController update the ShiftActivity table directly or do I need to transfer the data somehow to the ShiftAcitivityController when the form is submitted? Either way, can someone point me to an example? Thank you… Any help is greatly appreciated.
I found several questions on here relating to this but I'm not quite there. I'm trying to add a second UserProfile property to the already existing CourseRegistration class. When I try to perform the migration I get "The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_dbo.CourseRegistrations_dbo.UserProfile_InstructorId"
I thought I could solve it with some fluent configuration but it had no effect. Based on what I've read I think the issue is that there is existing data that won't allow this.
Question 1: I don't completely understand what it's complaining about and would like to understand it better if anyone could shed some light.
Question 2: Is there any workaround other than dropping the table or removing the data? I don't mind doing that this time, but I'm sure there are situations where that's not an option.
[Table("UserProfile")]
public class UserProfile
{
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int UserId { get; set; }
public string UserName { get; set; }
}
public class CourseRegistration
{
[Key]
public int RegistrationId { get; set; }
public int UserId { get; set; }
public int? InstructorId { get; set; }
public virtual UserProfile user { get; set; }
public virtual UserProfile Instructor { get; set; }
}
Thanks,
joel
See this, and try this:
public class CourseRegistration
{
[Key]
public int RegistrationId { get; set; }
public virtual UserProfile user { get; set; }
[ForeignKey("InstructorId")]
public virtual UserProfile Instructor { get; set; }
}