I have these method classes:
public class Links
{
[Key]
public int LID { get; set; }
public string Link { get; set; }
public string Type { get; set; }
public string Filename { get; set; }
public virtual int RessourceId { get; set; }
}
public class Ressource
{
[Key]
public int RessourceId { get; set; }
public string TitreR { get; set; }
public string Desc { get; set; }
//public int Position { get; set; }
public int Rating { get; set; }
public string Tags { get; set; }
public virtual int SectionId { get; set; }
public virtual int UserId { get; set; }
public virtual ICollection<Links> Links { get; set; }
}
public class Section
{
[Key]
public int SectionId { get; set; }
public string Titre { get; set; }
public virtual ICollection<Tags> Tags { get; set; }
public virtual ICollection<Ressource> Ressources { get; set; }
//public Section() { this.Tag=new List<string>(); }
}
And when I want to delete a Ressource, I have this error:
The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted.
error line:
_db.Entry(R).State = EntityState.Deleted;
_db.SaveChanges(); // error line
PS: It was working before I added the Filename attribute to the Links class... Any idea how to solve it? Thank you
Make foreign key nullable (i.e. change it's type from int to int?):
public virtual int? RessourceId { get; set; }
That means you can have links without resource.
Related
Two Tables One To Many
VehicleStatus {Id , LastVehicleStatusUpdateId}
VehicleStatusUpdated {Id, VehicleStatusId, IsResponse }
I need to make (one to zero or one) to last record in VehicleStatusUpdated ...
LastVehicleStatusUpdateId ==> Navigator To VehicleStatus
like This
How can i make it with Entity Framework Annotation ??!!
public class Vehicle : IEntity<int>
{
public int Id { get; set; }
[Required]
public string Name { get; set; }
public string Number { get; set; }
public virtual VehicleStatus VehicleStatus { get; set; }
}
public class VehicleStatus : IEntity<int>
{
[ForeignKey("Vehicle")]
public int Id { get; set; }
public virtual Vehicle Vehicle { get; set; }
public int? LastVehicleStatusUpdateId { get; set; }
[ForeignKey("LastVehicleStatusUpdateId")]
public virtual VehicleStatusUpdate LastVehicleStatusUpdate { get; set; }
public virtual List<VehicleStatusUpdate> VehicleStatusUpdates { get; set;
}
public class VehicleStatusUpdate : IEntity<int>
{
[ForeignKey("LastVehicleStatus")]
public int Id { get; set; }
public DateTime UpdatedTime { get; set; }
public bool IsResponse { get; set; }
public int VehicleStatusId { get; set; }
[ForeignKey("VehicleStatusId")]
public virtual VehicleStatus VehicleStatus { get; set; }
}
I Tried this i got =>
Unable to determine the relationship represented by navigation property 'VehicleStatus.LastVehicleStatusUpdate' of type 'VehicleStatusUpdate'. Either manually configure the relationship, or ignore this property using the '[NotMapped]' attribute or by using 'EntityTypeBuilder.Ignore' in 'OnModelCreating'.
I'm using EF core, and I have a many-to-many relationship between two entity
IotaProject <--> User
Here's entities & dto related to the question
public class IotaProject
{
[Key]
public int Id { get; set; }
[Required]
public string ProjectName { get; set; }
[Required]
public DateTime Create { get; set; }
public ICollection<ProjectOwnerJoint> Owners { get; set; } = new List<ProjectOwnerJoint>();
}
public class ProjectOwnerJoint
{
public int IotaProjectId { get; set; }
public IotaProject IotaProject { get; set; }
public int UserId { get; set; }
public User User { get; set; }
}
public class User
{
[Key]
public int Id { get; set; }
[Required]
public string FullName { get; set; }
[Required]
public string ShortName { get; set; }
[Required]
public string Email { get; set; }
public ICollection<ProjectOwnerJoint> OwnedProjects { get; set; } = new List<ProjectOwnerJoint>();
}
public class ApplicationDbContext : DbContext
{
public DbSet<IotaProject> IotaProjects { get; set; }
public DbSet<User> Users { get; set; }
public DbSet<ProjectOwnerJoint> ProjectOwnerJoint { get; set; }
}
public class IotaProjectDisplayDto
{
public int Id { get; set; }
public string ProjectName { get; set; }
public DateTime Create { get; set; }
public UserMinDto Owner { get; set; }
public int Count { get; set; }
public IEnumerable<UserMinDto> Reviewers { get; set; }
}
public class UserMinDto
{
public int Id { get; set; }
public string FullName { get; set; }
public string ShortName { get; set; }
}
Following LINQ is the problem, the LINQ purpose is to convert IotaProject to IotaProjectDisplayDto, and key part is that Owners property of IotaProject is ICollection and Owner property in IotaProjectDisplayDto is just one single element UserMinDto, so I only need to get the first element of IotaProject's Owners and that's FirstOrDefault() comes.
IEnumerable<IotaProjectDisplayDto> results = _db.IotaProjects.Select(x => new IotaProjectDisplayDto
{
Id = x.Id,
ProjectName = x.ProjectName,
Create = x.Create,
Owner = x.Owners.Select(y => y.User).Select(z => new UserMinDto { Id = z.Id, FullName = z.FullName, ShortName = z.ShortName }).FirstOrDefault()
});
return results;
it throws run-time exception
Expression of type 'System.Collections.Generic.List`1[ToolHub.Shared.iota.UserMinDto]' cannot be used for parameter
of type 'System.Linq.IQueryable`1[ToolHub.Shared.iota.UserMinDto]'
of method 'ToolHub.Shared.iota.UserMinDto FirstOrDefault[UserMinDto](System.Linq.IQueryable`1[ToolHub.Shared.iota.UserMinDto])' (Parameter 'arg0')
I'm guessing it's probably related to deferred execution, but after read some posts, I still can't resolve it.
Any tips would be appreciated.
Right now, the only way I can get this work is I change type of Owner property in IotaProjectDisplayDto into IEnumrable, which will no longer need FirstOrDefault() to immediate execution. And later on, I manually get the first element in the client to display.
This issue happened in Microsoft.EntityFrameworkCore.SqlServer 3.0.0-preview7.19362.6
I end up downgrade to EF core stable 2.2.6 as Ivan suggested in comment, and everything works fine.
My EF Code First model for some reason is not in sync with the db. I'm getting this error:
{"Invalid column name 'Type_Id1'."}
The field is actually called 'Type_Id' so I'm not sure from where that 1 comes up. I have the table column called as Type_Id and also I've added a Type_Id in my type entity model.
Why might I be getting that error message, plus why I'm getting 1 at the end of the name?
Update
My Task class:
public class Task
{
public Task()
{
Language = 1;
Grades = new HashSet<Grade>();
Categories = new HashSet<Category>();
Subjects = new HashSet<Subject>();
Rooms = new Collection<Room>();
Tools = new Collection<Tool>();
}
[Key]
public int Id { get; set; }
public string Description { get; set; }
public virtual TaskType Type { get; set; }
public string Rules { get; set; }
[Required]
[StringLength(200), MinLength(1)]
public string Name { get; set; }
public int PreperationTime { get; set; }
public int InstructionTime { get; set; }
public int TaskTime { get; set; }
public int Type_Id { get; set; }
public string VideoLink { get; set; }
[Required]
public int Language { get; set; }
public int? MinimumParticipants { get; set; }
public int? MaximumParticipants { get; set; }
public int? Rating { get; set; }
[Required]
public string CreatedBy { get; set; }
public virtual ICollection<Grade> Grades { get; set; }
public virtual ICollection<Category> Categories { get; set; }
public virtual ICollection<Subject> Subjects { get; set; }
public virtual ICollection<Room> Rooms { get; set; }
public virtual ICollection<Tool> Tools { get; set; }
}
DBContext class:
public ApplicationDbContext() : base("DefaultConnection", false)
{
}
public DbSet<Task> Tasks { get; set; }
public DbSet<TaskType> TaskTypes { get; set; }
public static ApplicationDbContext Create()
{
return new ApplicationDbContext();
}
You need to add the FK attribute on your navigation property. EF is creating Type_Id1 because Type_Id already exists (although it can't tell by convention it is the FK).
[ForeignKey("Type_Id")]
public virtual TaskType Type { get; set; }
https://msdn.microsoft.com/en-us/data/jj591583.aspx#Relationships
I have some problems when updating my model. This is my update code:
public void Update(Class #class)
{
var updatedClass = context.Classes.Where(c => c.ClassId == #class.ClassId).FirstOrDefault();
updatedClass.ClassPriceTypeId = #class.ClassPriceTypeId;
updatedClass.ClassType = #class.ClassType;
updatedClass.Name = #class.Name;
updatedClass.Title = #class.Title;
updatedClass.MetaTag = #class.MetaTag;
updatedClass.MetaDescription = #class.MetaDescription;
updatedClass.UrlSafe = #class.UrlSafe;
updatedClass.Header = #class.Header;
updatedClass.Margin = #class.Margin;
updatedClass.ImageName = #class.ImageName;
updatedClass.GroupId = #class.GroupId;
updatedClass.IsPublished = #class.IsPublished;
context.SaveChanges();
}
First problem is that I have made LazyLoadingEnabled=false but after fetching updatedClass the relational properties like Group is not null.
Second problem is that in some of #class objects I can easily update my entity but in some others I see this error:
The operation failed: The relationship could not be changed because
one or more of the foreign-key properties is non-nullable. When a
change is made to a relationship, the related foreign-key property is
set to a null value. If the foreign-key does not support null values,
a new relationship must be defined, the foreign-key property must be
assigned another non-null value, or the unrelated object must be
deleted.
Update
This is Class model:
public class Class
{
public int ClassId { get; set; }
public int GroupId { get; set; }
public int ClassPriceTypeId { get; set; }
public string Name { get; set; }
public string Title { get; set; }
public string MetaTag { get; set; }
public string MetaDescription { get; set; }
public string UrlSafe { get; set; }
public string Header { get; set; }
public string ImageName { get; set; }
public int Margin { get; set; }
public string ClassType { get; set; }
public bool IsPublished { get; set; }
public virtual Group Group { get; set; }
public virtual List<Product> Products { get; set; }
public virtual List<Comparing.Model.Price.Price > Prices { get; set; }
public virtual ClassPriceType.ClassPriceType ClassPriceType { get; set; }
public virtual List<Garanty> Garanties { get; set; }
public virtual List<PhoneModel> PhoneModels { get; set; }
public virtual List<ClassPartner> ClassPartners { get; set; }
public virtual List<Content> Contents { get; set; }
}
And this is Group model:
public class Group
{
public int GroupId { get; set; }
public int SectionId { get; set; }
public string Name { get; set; }
public string Title { get; set; }
public string MetaTag { get; set; }
public string MetaDescription { get; set; }
public string UrlSafe { get; set; }
public string Header { get; set; }
public string ImageName { get; set; }
public bool IsPublished { get; set; }
public virtual Section Section { get; set; }
public virtual List<Class> Classes { get; set; }
}
Can anyone help me about the problem?
I guess, you are trying to update a primary key field which is having a relation ship with other foreign key with not null constraint. I guess you need to use update cascade.
I've got a definition like below and essentially, I want to create this in the EmailAccount class:
public EmailUser? EmailUserAccountInfo {get;set;}
the compiler gives me an error about non-nullable types. My goal is I want to make the EmailUser optional. I'm kind of confused because I can set EmailUserAccountInfo = null directly.
var r = new EmailAccount()
{
EmailUserAccountInfo = null,
Id = 1001
};
public class EmailAccount
{
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
public EmailUser EmailUserAccountInfo { get; set; }
}
public class EmailUser
{
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
public EmailAccount EmailAcount { get; set; }
public string EmailAddress { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string ZipCode { get; set; }
public string City { get; set; }
public string State { get; set; }
public int Temperature { get; set; }
public string WeatherString { get; set; }
public ImageDetail ImageOfUser { get; set; }
}
You can do this if you add a foreign key and you mark that nullable:
public class EmailAccount
{
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
// Foreign key
public int? EmailUserAccountInfoId { get; set; }
// Navigation property
public virtual EmailUser EmailUserAccountInfo { get; set; }
}
See this document about naming conventions for Code-First. (Scroll down to Relationship Convention)