I am using Entity Framework 6 with Generic Repository and DTOs.
I want to create new entities via navigation property.
Here is my model:
public partial class Project
{
public Project()
{
this.ProjectAssets = new List<ProjectAsset>();
}
public int ProjectID { get; set; }
public string Name { get; set; }
public virtual ICollection<ProjectAsset> ProjectAssets { get; set; }
}
public partial class Asset
{
public Asset()
{
this.Revisions = new List<Revision>();
}
public int AssetID { get; set; }
public string Name { get; set; }
public short Type { get; set; }
public virtual ICollection<Revision> Revisions { get; set; }
}
public partial class ProjectAsset
{
public int MappingID { get; set; }
public int ProjectID { get; set; }
public int AssetID { get; set; }
public virtual Asset Asset { get; set; }
}
I have already created Project. And if i am creating new Asset, then create Project Asset with AssetID from just created Asset, it's OK, but i have to re-fetch Project from DB.
I want to do it in one transaction, like that:
Project.ProjectAssets.Add(new ProjectAsset(new Asset((short)type, fileName)));
ServiceLocator.Default.ResolveType<IPipeLine>().Update(Project);
public void Update<TEntity>(TEntity entity) where TEntity : class
{
var fqen = GetEntityName<TEntity>();
object originalItem;
var key = ((IObjectContextAdapter)DbContext).ObjectContext.CreateEntityKey(fqen, entity);
if (((IObjectContextAdapter)DbContext).ObjectContext.TryGetObjectByKey(key, out originalItem))
((IObjectContextAdapter)DbContext).ObjectContext.ApplyCurrentValues(key.EntitySetName, entity);
//DbContext.Entry(entity).State = EntityState.Modified;
}
But after SaveChanges there is no record in DB, and MappingID still 0.
I thought that ApplyCurrentValues must work with Navigation Properties.
Is there any good way to solve that problem?
EDIT:
I accessing DAL throughBusiness Entities with contain the same properties, but they also implement INotifyPropertyChanged and other WPF stuff. So i think i can subscribe to CollectionChanged event and manualy create/delete entities from navigation property. And in property setters i can call update, but i think it can strongly decrease perfomance.
Related
I have these models and context in my application :
public class Department
{
public int Id { get; set; }
public string Name { get; set;}
public virtual ICollection<Student> Students { get; set; }
}
public class Student
{
public int Id { get; set; }
public string Name { get; set; }
public virtual Department Department { get; set; }
}
public class TestContext : DbContext
{
public DbSet<Student> Students { get; set; }
public DbSet<Department> Departments { get; set; }
}
Below is my code in Program.cs class :
class Program
{
static void Main(string[] args)
{
using (var context = new TestContext())
{
var students = context.Students.SqlQuery("Select * from dbo.Students").ToList();
context.Departments.Load();
Console.WriteLine(students[0].Department.Name);
Console.ReadLine();
}
}
}
Although related object - Department is loaded in the context by the line - context.Departments.Load(), still when the department name is printed in console entity framework fires a query in the database to fetch the related object. Shouldnt this query for related object fetching not be fired since the objects are already loaded in the context. ?
If i change the code to below -
var students = context.Students.ToList();
context.Departments.Load();
Console.WriteLine(students[0].Department.Name);
Then when u access student[0].Department.Name , Ef doestnot fire a sql query to load department property.
Apparently Change Tracker relationship fix-up doesn't work with the combination of Independent Associations and raw SQL queries.
To fix just add Foreign Key property to Student. eg
public class Student
{
public int Id { get; set; }
public string Name { get; set; }
public int DepartmentId { get; set; }
public virtual Department Department { get; set; }
}
I try to create the following database design with EF Core (code-first)
Entity "Recipe" can have a list of type "Resource"
Entity "Shop" can have a single "Resource"
Entity "InstructionStep" can have a list of type "Resource"
If I delete a resource from the "Recipe", "InstructionStep" (collections) or from the "Shop" (single-property) then the corresponding "Resource" entity should be also deleted. (Cascade Delete)
I already tried several things with and without mapping tables but none of my approach was successful.
Another idea was to have a property "ItemRefId" in the "Resource" entity to save the "RecipeId/ShopId/InstructionStepId" but I don't get it to work...
Example Classes:
public class Recipe
{
public int RecipeId { get; set; }
public string Title { get; set; }
public ICollection<RecipeResource> Resources { get; set; } = new List<RecipeResource>();
}
public class Shop
{
public int ShopId { get; set; }
public string Title { get; set; }
public Resource Logo { get; set; }
}
public class Resource
{
public int ResourceId { get; set; }
public string Path { get; set; }
public int ItemRefId { get; set; }
}
public class InstructionStep
{
public string InstructionStepId { get; set; }
public string Title { get; set; }
public ICollection<RecipeResource> Resources { get; set; } = new List<RecipeResource>();
}
Any suggestions? Many thanks in advance.
That's not cascade delete. Cascade delete would be when a Recipe is deleted, all of the related Resources are deleted as well.
In EF Core 3, you can use Owned Entity Types for this. The generated relational model is different from what you are proposing, in that Recipe_Resource and InstructionStep_Resource will be seperate tables, and Shop.Logo will be stored in columns on the Shop table. But that's the correct relational model. Having one Resource table with some rows referencing a Recipe and some rows referencing an InstructionStep is a bad idea.
This scenario is sometimes called a "Strong Relationship" where the identity of the related entity is dependent on the main entity, and should be implemented in the relational model by having the the Foreign Key columns be Primary Key columns on the dependent entity. That way there's no way remove a Recipe_Resource without deleting it.
eg
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using System.Collections.Generic;
using System.Linq;
namespace EfCore3Test
{
public class Recipe
{
public int RecipeId { get; set; }
public string Title { get; set; }
public ICollection<Resource> Resources { get; } = new List<Resource>();
}
public class Shop
{
public int ShopId { get; set; }
public string Title { get; set; }
public Resource Logo { get; set; }
}
public class Resource
{
public int ResourceId { get; set; }
public string Path { get; set; }
public int ItemRefId { get; set; }
}
public class InstructionStep
{
public string InstructionStepId { get; set; }
public string Title { get; set; }
public ICollection<Resource> Resources { get; } = new List<Resource>();
}
public class Db : DbContext
{
public DbSet<Recipe> Recipes { get; set; }
public virtual DbSet<Shop> Shops { get; set; }
public virtual DbSet<InstructionStep> InstructionSteps { get; set; }
private static readonly ILoggerFactory loggerFactory = LoggerFactory.Create(builder =>
{
builder.AddFilter((category, level) =>
category == DbLoggerCategory.Database.Command.Name
&& level == LogLevel.Information).AddConsole();
});
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseLoggerFactory(loggerFactory)
.UseSqlServer("Server=.;database=EfCore3Test;Integrated Security=true",
o => o.UseRelationalNulls());
base.OnConfiguring(optionsBuilder);
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<Shop>().OwnsOne(p => p.Logo);
modelBuilder.Entity<InstructionStep>().OwnsMany(p => p.Resources);
modelBuilder.Entity<Recipe>().OwnsMany(p => p.Resources);
}
}
class Program
{
static void Main(string[] args)
{
using var db = new Db();
db.Database.EnsureDeleted();
db.Database.EnsureCreated();
var r = new Recipe();
r.Resources.Add(new Resource() { ItemRefId = 2, Path = "/" });
db.Recipes.Add(r);
db.SaveChanges();
r.Resources.Remove(r.Resources.First());
db.SaveChanges();
var s = new Shop();
s.Logo = new Resource { ItemRefId = 2, Path = "/" };
db.Shops.Add(s);
db.SaveChanges();
s.Logo = null;
db.SaveChanges();
}
}
}
I have SQLite db and these EF models and context.
Models and Context
public class CardHolder
{
public int CardHolderId { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string PhoneNumber { get; set; }
public string EmailAddress { get; set; }
public string TenantName { get; set; }
public ICollection<AccessCard> AccessCards { get; set; }
}
public class AccessCard
{
public int AccessCardId { get; protected set; }
public CardHolder CardHolder { get; set; }
public DateTime ActivationDate { get; protected set; }
public bool ActivationProcessed { get; set; }
public DateTime? DeactivationDate { get; protected set; }
public string DeactivationReason { get; set; }
public bool DeactivationProcessed { get; set; }
}
public class MyContext : DbContext
{
public DbSet<CardHolder> CardHolders { get; set; }
public DbSet<AccessCard> AccessCards { get; set; }
}
And the Main program
class Program
{
static void Main(string[] args)
{
using (var db = new MyContext())
{
var cardHolders = db.CardHolders.Include("AccessCard").ToList();
}
}
}
Question1: Why do I get this exception
System.InvalidOperationException: 'A specified Include path is not
valid. The EntityType 'SQLiteDemo.Models.CardHolder' does not declare
a navigation property with the name 'AccessCard'.'
If I replace it with
var cardHolders = db.CardHolders.Include("AccessCards").ToList();
I get another error:
SQL logic error no such column: Extent2.CardHolder_CardHolderId
What is wrong with Entity Framework?
Question2: Why cant I use arrow function in Include statement, it doesnt compile at all?
var cardHolders = db.CardHolders.Include(x => x.AccessCards).ToList();
Question3: Why do I need to use Include at all if my ICollection association property AccessCards is NOT virtual - that means eager loading must work by itself!
Why the hell it is so problematic and buggy? Nothing works as it should :(
1 - You have a typo as you have already determined :)
1B - "SQL logic error no such column: Extent2.CardHolder_CardHolderId"
EF isn't finding your FK. You could add it to your AccessCard model:
public int CardHolderId { get; set; }
2 - You need to pull in the LINQ extensions. Make sure you have both of these using statements at the top:
using System.Data.Entity;
using System.Linq;
3 - You, like many others, are misunderstanding lazy loading. Eager loading still requires an Include() to fetch related data. Lazy loading only fetches the relations when you access them.
The method is really simple and I don't see what am I missing...
public int SaveEvent(Data.Models.Event evnt)
{
db.Events.Add(evnt);
db.SaveChanges();
return evnt.EventId;
}
here is the object declaration:
public class Event
{
public int EventId { get; set; }
public string Name { get; set; }
public ICollection<EventTag> EventTags { get; set; }
}
The evnt object contains a property name EventTags that contains 6 new elements.
The evnt is inserted in the database but not the EventTag... any idea ? no error nothing. just the EventTag are not added...
public class EventDbContext : DbContext
{
public DbSet<Event> Events { get; set; }
public DbSet<EventTag> EventTags { get; set; }
public DbSet<Tag> Tags { get; set; }
}
Here is a screenshot of the value:
If the EventTags are not being added to the database you may need to manually specify the EntityState for each tag.
public int SaveEvent(Data.Models.Event evnt)
{
foreach(var tag in evnt.EventTags)
{
db.Entry(tag).State = EntityState.Added;
}
db.Events.Add(evnt);
db.SaveChanges();
return evnt.EventId;
}
You might also want to update your class definition and set the EventTags property as virtual.
public class Event
{
public int EventId { get; set; }
public string Name { get; set; }
public virtual ICollection<EventTag> EventTags { get; set; }
}
In your screenshot it looks like the tags are loading, but not the Location property on the tags. If that's the case, then make sure to set the Location property to virtual as well.
Assume that I have the following little console application which uses Entity Framework 5:
class Program {
static void Main(string[] args) {
using (var ctx = new ConfContext()) {
var personBefore = ctx.People.First();
Console.WriteLine(personBefore.Name);
personBefore.Name = "Foo2";
ctx.SaveChanges();
var personAfter = ctx.People.First();
Console.WriteLine(personAfter.Name);
}
Console.ReadLine();
}
}
public class ConfContext : DbContext {
public IDbSet<Person> People { get; set; }
public IDbSet<Session> Sessions { get; set; }
}
public class Person {
[Key]
public int Key { get; set; }
public string Name { get; set; }
public string Surname { get; set; }
public DateTime? BirthDate { get; set; }
public ICollection<Session> Sessions { get; set; }
}
public class Session {
[Key]
public int Key { get; set; }
public int PersonKey { get; set; }
public string RoomName { get; set; }
public string SessionName { get; set; }
public Person Person { get; set; }
}
As you can see, I am changing the name of the record and saving it. It works but it feels like magic to me. What I am doing in all of my applications is the following one (to be more accurate, inside the Edit method of my generic repository):
static void Main(string[] args) {
using (var ctx = new ConfContext()) {
var personBefore = ctx.People.First();
Console.WriteLine(personBefore.Name);
personBefore.Name = "Foo2";
var entity = ctx.Entry<Person>(personBefore);
entity.State = EntityState.Modified;
ctx.SaveChanges();
var personAfter = ctx.People.First();
Console.WriteLine(personAfter.Name);
}
Console.ReadLine();
}
There is no doubt that the second one is more semantic but is there any other obvious differences?
Well the second code block where you explicitly set the entity state is redundant, as the change tracker already knows that the entity is modified because the context knows about the entity (as you query the context to retrieve the entity).
Setting (or painting) the state of the entity would be more useful when working with disconnected entities, for example in an n-tier environment where the entity was retrieved in a different context and sent to a client for modification, and you wish to mark those changes back on the server using a different context.
Otherwise, the first code block is cleaner in my opinion.