I have two model
1)
public class Indicator
{
public long ID { get; set; }
public string Name { get; set; }
public int MaxPoint { get; set; }
public string Comment { get; set; }
public DateTime DateChanged { get; set; }
public DateTime DateCreated { get; set; }
public virtual IList<CalculationType> CalculationTypes { get; set; }
public virtual IList<TestEntity> TestEntitys { get; set; }
public virtual IndicatorGroup IndicatorGroup { get; set; }
}
2)
public class CalculationType
{
public long ID { get; set; }
public string UnitName { get; set; }
public int Point { get; set; }
public DateTime DateCreated { get; set; }
public DateTime DateChanged { get; set; }
public virtual Indicator Indicator { get; set; }
public virtual IList<Сalculation> Calculations { get; set; }
}
I executing this code
var indicator = DataContext.Indicators.FirstOrDefault(i => i.ID == indicatorID);
var test = DataContext.CalculationTypes.FirstOrDefault();
first line return null on navigation property CalculationTypes
Second line return empty collection. Why?
UPDATE
snapshot database
project link https://github.com/wkololo4ever/Stankin
added Calculation
public class Сalculation
{
public long ID { get; set; }
public virtual CalculationType CalculationType { get; set; }
public virtual ApplicationUser Creator { get; set; }
}
1) Is Lazy Loading enabled? If not, you need to explicitly load your navigation properties with the '.Include' syntax.
2) Are you sure EF should be able to detect that relation? Did you use Code First or Database First?
Edit: 3) Are you sure there is data in your database and that the foreign key from Indicator to IndicatorGroup has a value for that specific record? I am saying this because the value "null" is valid if there is simply no data.
P.S. If you do not see a foreign key on Indicator called "IndicatorGroupId", there might be an "IndicatorId" on the table "IndicatorGroup", in which case - going from the names you provided - your database is misconfigured and you will need to use fluent syntax or data attributes to instruct EF on how to make the foreign keys.
Try this:
DbContext.Configuration.ProxyCreationEnabled = true;
DbContext.Configuration.LazyLoadingEnabled = true;
If DbContext.Configuration.ProxyCreationEnabled is set to false, DbContext will not load child objects for some parent object unless Include method is called on parent object. Setting DbContext.Configuration.LazyLoadingEnabled to true or false will have no impact on its behaviours.
If DbContext.Configuration.ProxyCreationEnabled is set to true, child objects will be loaded automatically, and DbContext.Configuration.LazyLoadingEnabled value will control when child objects are loaded.
I think this is problem:
Edit: 3) Are you sure there is data in your database and that the
foreign key from Indicator to IndicatorGroup has a value for that
specific record? I am saying this because the value "null" is valid if
there is simply no data.
P.S. If you do not see a foreign key on Indicator called
"IndicatorGroupId", there might be an "IndicatorId" on the table
"IndicatorGroup", in which case - going from the names you provided -
your database is misconfigured and you will need to use fluent syntax
or data attributes to instruct EF on how to make the foreign keys.
Try to this and make sure foreign key is corrected.
public class CalculationType
{
public long ID { get; set; }
public string UnitName { get; set; }
public int Point { get; set; }
public DateTime DateCreated { get; set; }
public DateTime DateChanged { get; set; }
[ForeignKey("IndicatorID")]
public string IndicatorId { get; set; } //this is the foreign key, i saw in your database is: Indicator_ID, avoid this, rename it to IndicatorID or IndicatorId
public virtual Indicator Indicator { get; set; }
public virtual IList<Сalculation> Calculations { get; set; }
}
Same behavior, but different root cause than selected answer:
Navigation property can also be null if you turned off myContext.Configuration.AutoDetectChangesEnabled
Very obvious, but this got me when I was implementing some performance improvments.
Check this out: Navigation Property With Code First . It mentions about why navigation property is null and the solutions of it.
By default, navigation properties are null, they are not loaded by
default. For loading navigation property, we use “include” method of
IQuearable and this type of loading is called Eager loading.
Eager loading: It is a process by which a query for one type of entity
loads the related entities as a part of query and it is achieved by
“include” method of IQueryable.
I experienced this issue, where navigation properites were not loaded, even when the Include statement was present.
The problem was caused by string-comparison differences between SQL Server and EF6 using .NET. I was using a VARCHAR(50) field as the primary key in my customers table and also, as a foreign key field in my audit_issues table. What I did not realize was that my keys in the customers table had two additional white space characters on the end; these characters were not present in my audit_issues table.
However, SQL Server will automatically pad whitespace for string comparisons. This applies for WHERE and JOIN clauses, as well as for checks on FOREIGN KEY constraints. I.e. the database was telling me string were equivalent and the constraint passed. Therefore I assumed that they actually were exactly equal. But that was false. DATALENGTH of one field = 10, while the DATALENGTH of the other = 8.
EF6 would correctly compose the SQL query to pull the foreign key related fields and I would see them both in the generated Sql query and in the results. However, EF6 would silently fail when loading the Navigation Properties because .NET does not consider those strings equal. Watch out for whitespace in string-type foreign key fields!.
This article helped me.
In sum :
Install-Package Microsoft.EntityFrameworkCore.Proxies
In Startup.cs
using Microsoft.EntityFrameworkCore;
public void ConfigureServices(IServiceCollection services)
{
...
services.AddDbContext<MyDbContext>(builder =>
{
builder.UseLazyLoadingProxies(); // <-- add this
}, ServiceLifetime.Singleton);
This is a variant of Keytrap's answer. Using .NET 6 and EF Core 6, I created a ContextPartials.cs for any custom configurations that I don't want EF's Scaffold command to overwrite:
Required Package:
Install-Package Microsoft.EntityFrameworkCore.Proxies
Code (ContextPartials.cs):
// NOTE: I am not using the new file-scoped namespace on purpose
namespace DataAccess.Models.MyDatabase
{
// NOTE: This is a partial outside of the generated file from Scaffold-DbContext
public partial class MyDatabaseContext
{
// NOTE: This enables foreign key tables to become accessible
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
=> optionsBuilder.UseLazyLoadingProxies();
}
}
Related
I have a solution which uses Entity Framework to insert invoices to a database table. These invoices reference an order, which in turn also references an order item collection.
In this instance I am trying to add an order to the database, however the code is inside a new DbContext and so I need to attach the order and order items to the context, as these already exist in the database and shouldn't be re-added.
I've cut down the model properties for the sake of demonstration:
public class Invoice {
[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int InvoiceId { get; set; }
public string OrderNumber { get; set; }
...
public virtual List<InvoiceLineItem> LineItems { get; set; }
}
public class InvoiceLineItem {
[Key]
public int Id { get; set; }
...
public ShopifyOrderItem { get; set; }
}
public class ShopifyOrder {
[Key, DatabaseGenerated(DatabaseGeneratedOption.None)]
public long Id { get; set; }
public int OrderNumber { get; set; }
...
public OrderInvoiceStatus InvoiceStatus { get; set; }
public virtual List<ShopifyOrderItem> OrderItems { get; set; }
}
public class ShopifyOrderItem {
[Key, DatabaseGenerated(DatabaseGeneratedOption.None)]
public long Id { get; set; }
...
[Required]
public virtual ShopifyOrder ShopifyOrder { get; set; }
}
In the invoice engine, I'm running the following code for each invoice to add it to the database:
ShopifyOrder order = await db.ShopifyOrders.SingleOrDefaultAsync(x => x.OrderNumber.ToString() == inv.OrderNumber);
if (order != null) {
// Attach marketplace entity to the invoice to avoid duplicate primary key exceptions
db.Marketplaces.Attach(inv.Marketplace);
db.Invoices.Add(inv);
order.InvoiceStatus = OrderInvoiceStatus.InProgress;
}
I've tried a number of methods to try and attach the states, however they all throw errors.
inv.LineItems.ForEach(li => {
db.Entry(li).State = EntityState.Unchanged;
db.Entry(li.ShopifyOrderItem).State = EntityState.Unchanged;
db.Entry(li.ShopifyOrderItem.ShopifyOrder).State = EntityState.Modified;
});
The above code returns the following error on save:
EntityFramework: Saving or accepting changes failed because more than one entity of type 'TorroModels.ShopifyOrder' have the same primary key value. Ensure that explicitly set primary key values are unique. Ensure that database-generated primary keys are configured correctly in the database and in the Entity Framework model.
What is the best way to attach the LineItems/ShopifyOrderItems without trying to attach the ShopifyOrder connected property multiple times?
Sorry to say but it seems that you need to follow the best practice first when constructing a relationship. You may follow this link :
http://www.entityframeworktutorial.net/entity-relationships.aspx
In short :
Avoid using only "Id" in every entity, or you can use attributes to map between the physical name and the property name
It seems that you have circular references here, so maybe you could simplify it first
Next, you can read this link :
http://www.entityframeworktutorial.net/EntityFramework5/attach-disconnected-entity-graph.aspx
if you need to know more about what's the best practice of attaching entities, but in my opinion, just don't abuse this feature, because using normal CRUD should be sufficient most of the time.
I'm sorry I cannot help you more than this, because of lack of information I may need, and with my reputation I still cannot comment directly in your post to ask for it.
I recently delete a column ConversationId from my tables. When I start to debug my service and try to save I am getting an error:
Invalid column name 'ConversationId'.
Code:
public class AstootContext : DbContext
{
public AstootContext(DbContextOptions<AstootContext> options)
: base(options)
{ }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
}
public DbSet<ServiceRequest> ServiceRequests { get; set; }
}
And my entity looks like this:
public class ServiceRequest
{
public int Id { get; set; }
public int SenderUserId { get; set; }
public int PriceTypeId { get; set; }
public decimal Price { get; set; }
public bool IsAccepted { get; set; }
public DateTime Created { get; set; }
public int MessageId { get; set; }
}
All references to ConversationId were removed from the code, I've rebuilt, yet I'm still getting this error and I don't understand why.
This is my SQL Server table as you can see there is no ConversationId:
Is there a secret cache that I need to delete or something I have to run to update this?
EF Core is code based ORM, with the most important here being the M - Mapper. It doesn't matter what the actual database structure is, the important is what EF *thinks** it is based on your code model (entity classes and their properties, combined with data annotations, fluent configuration and set of conventions).
So the problem should originate from code. Since you've removed the explicit property, it should be caused by shadow property. And as explained in the documentation link, shadow properties are usually introduced by convention from relationships:
Shadow properties can be created by convention when a relationship is discovered but no foreign key property is found in the dependent entity class. In this case, a shadow foreign key property will be introduced.
The documentation also explains the naming rules applied in different scenarios.
A shadow property called ConversationId can be introduced in a several ways, but according to the provided information, the most likely cause is to have an entity class called Conversation defining one-to-many relationship with ServiceRequest by having a collection type navigation property:
public class Conversation
{
public int Id { get; set; }
// ...
public ICollection<ServiceRequest> ServiceRequests { get; set; }
}
Which according to your comment was indeed the case.
For completeness, here are some other possible scenarios generating such property:
(1) No collection navigation property in Conversation, reference navigation property in ServiceRequest:
public class Conversation
{
public int Id { get; set; }
// ...
}
public class ServiceRequest
{
// ...
public Conversation Conversation { get; set; }
}
(2) No navigation properties in Conversation and ServiceRequest, fluent configuration:
modelBuilder.Entity<Conversation>()
.HasMany<ServiceRequest>();
or
modelBuilder.Entity<ServiceRequest>()
.HasOne<Conversation>();
or variations of the above.
(3) No relationship involved, shadow property created through fluent configuration:
modelBuilder.Entity<ServiceRequest>()
.Property<int>("ConversationId");
First off, I'm new to the Entity Framework and am migrating an existing project from a database framework that I wrote myself so I have a fair amount of flexibility in the solution I choose.
From what I've researched so far everything appears to be set up correctly. However, when my database is constructed, the table for a helper class I wrote has no columns in it (outside of its primary key). The most simplified version of the classes are included below with their relationships defined in the fluent API.
Classes
public class Concept
{
public long ID { get; set; }
[Index(IsUnique = true), MaxLength(255)]
public string Name { get; set; }
}
public class Tag
{
public long ID { get; set; }
public virtual Content Subject { get; set; }
public virtual Concept Concept { get; set; }
}
public class Helper
{
public long ID { get; set; }
public virtual Content Subject { get; set; }
public virtual List<Tag> Instances { get; set; }
// Helper functionality
}
public class Content
{
public long ID { get; set; }
public virtual Helper Helper { get; set; }
public Content() { Helper = new Helper() { Subject = this }; }
}
Context
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Tag>()
.HasRequired(t => t.Concept);
modelBuilder.Entity<Tag>()
.HasRequired(t => t.Subject);
modelBuilder.Entity<Helper>()
.HasRequired(t => t.Subject)
.WithRequiredDependent(c => c.Helper);
modelBuilder.Entity<Helper>()
.HasMany(t => t.Instances);
modelBuilder.Entity<Content>()
.HasRequired(c => c.Helper)
.WithRequiredPrincipal();
base.OnModelCreating(modelBuilder);
}
Program.cs
static void Main(string[] args)
{
Content content = null;
using (var context = new Context())
{
content = context.Content.Find(1);
if (content == null)
{
content = new Content();
context.Content.Add(content);
context.Helper.Add(content.Helper);
context.SaveChanges();
}
}
}
It's also worth mentioning that when the data is saved, the Helper is assigned an ID but on loading the parent class (Content) the second time around, the Helper is not lazy loaded as I would expect from the 'virtual' keyword. I suspect that this is caused by the same issue causing the absence of data in the table.
I have tried both the data annotation and fluent API approaches that EF provides but it seems that there is something fundamental that I am misunderstanding. I would like to retain this helper class as it helps organize the code far better.
As I have spent a fair amount of time researching these relationships / APIs, and scouring Google / SO without found anything to solve this issue in particular any help would be greatly appreciated!
Updated: Solution
Thanks to a question in the comments, I realized that I was expecting to see the keys of a many-to-many relationship in the tables for the entity types themselves (i.e. in the Helpers table). However, in a many-to-many relationship, the keys will always be placed in a separate table (concatenation of type names) which was not being previously created.
By adding '.WithMany();' to the Helper section of the OnModelCreating function as below
modelBuilder.Entity<Helper>()
.HasMany(t => t.Instances)
.WithMany();
the many-to-many relationship became properly defined and the HelperTags table generated as expected. This is due to the fact that the many-to-many relationship is one way (Helpers always refer to Tags, Tags never refer to Helpers). This is also why the 'WithMany' does not have any arguments (since no Helper properties exist in the Tag class). Fixing this simple oversight solved the problem!
You are probably working harder than you need to in the on ModelCreate. You should probably redesign your classes use Identifiers, like this:
public class Tag
{
public long Id { get; set; }
public long SubjectId { get; set; }
public long ConceptId { get; set; }
public virtual Content Subject { get; set; }
public virtual Concept Concept { get; set; }
}
You need to keep the ID names the EXACT same as the object names + Id and EF will magically link everything up. If you don't want them required then make the id nullable (C# 6 == long? SubjectId).
Also, I have changed the ID -> Id; I have no idea if this matters. At one point I remember having to do that to get things working (it was YEARS ago) and I have been doing it that way ever since.
Consider reading:
Entity Framework Code First Conventions
relationship Convention
In addition to navigation properties, we recommend that you include
foreign key properties on the types that represent dependent objects.
Any property with the same data type as the principal primary key
property and with a name that follows one of the following formats
represents a foreign key for the relationship:
<navigation property name><principal primary key property name>
<principal class name><primary key property name>
<principal primary key property name>
If multiple matches are found then precedence is given in the order
listed above.
Foreign key detection is not case sensitive.
Sample Code from MSDN:
In the following example the navigation properties and a foreign key are used to define the relationship between the Department and Course classes.
public class Department
{
// Primary key
public int DepartmentID { get; set; }
public string Name { get; set; }
// Navigation property
public virtual ICollection<Course> Courses { get; set; }
}
public class Course
{
// Primary key
public int CourseID { get; set; }
public string Title { get; set; }
public int Credits { get; set; }
// Foreign key
public int DepartmentID { get; set; }
// Navigation properties
public virtual Department Department { get; set; }
}
I am using EntityFramework for the first time and maybe this question is so simple...I've used code first method..I have a Class Personnel which looks like this:
public class Personnel
{
public string Id { set; get; }
public int Code { set; get; }
public string Name { set; get; }
public int Type { set; get; }
public JobTitle Title { set; get; }
}
and the JobTitle class:
public class JobTitle
{
public string Id { set; get; }
public int Number { set; get; }
public string Title { set; get; }
public List<Personnel> Personnels { set; get; }
}
which the last property in Personnel Class is a foreign key in personnel table of course..my problem is when I want to retrieve all personnels ( or a personnel ) from DB using lambda expression..the foreign key object is null..the lambda expression is like below:
Context.ContextInstance.Personnels.ToList();
and if I change the expression to this the foreign key object is not null any more.
Context.ContextInstance.Personnels.Include("Title").ToList();
is it the right way??..is there any better way??..I supposed that EF will automatically understand that!!!!..if there are more than 1 FK then I have to use Include for all of them?? please help me to understand.
Thanks
This is due to lazy loading. When you call Context.ContextInstance.Personnels.ToList(); this will fetch all personnel's but Title will not fetch until it get instanced, so make it virtual to get it.
or, you can disable lazy loading by
public MyEntitiesContext() : base("name=MyEntitiesContext", "MyEntitiesContext") {
this.Configuration.LazyLoadingEnabled = false;
}
Doing this will get all related data from context. Using "include" is loading on demand, when you specify properties you want to query.
Virtual keyword allows entity framework runtime create dynamic proxies for your entity classes and their properties, and by that support lazy loading. Without virtual, lazy loading will not be supported, and you get null on collection properties.
If your JobTitle property would be defined as virtual, you wouldn't need to use include.
It's really good explained here: Entity Framework 4.1 Virtual Properties
I'm trying so simplify my problem here, but basically I'm trying to map 2 entities however i don't have a Foreign Key in the database set, since the column could be null. When I try to do an insert on the parent, I'm getting the following error:
object references an unsaved transient instance - save the transient
instance before flushing or set cascade action for the property to
something that would make it autosave.
This is what I have so far:
My entities
public class DocumentDraft
{
public virtual Guid Id { get; set; }
public virtual string Subject { get; set; }
public virtual string ReferenceNo { get; set;}
public virtual DocumentType DocumentType { get; set; }
}
public class DocumentType
{
public virtual short Id { get; set; }
public virtual string Description { get; set; }
}
Mapping
public class DocumentDraftMap : ClassMap<DocumentDraft>
{
public DocumentDraft()
{
// other mappings ...
References(x => x.DocumentType)
.Columns("DocumentTypeId")
.Nullable()
.Not.LazyLoad()
.NotFound.Ignore(); // <-- added this since the value could be null and it throws an error
}
}
I tried specifying Cascade.None() in the mapping, but I'm getting the same result. Basically what happens is that a null value is attempted at being inserted in the DocumentType, and I don't want this (I want to insert null in the parent table, but I don't want to touch the child tables at all, I don't want this to cascade).
I've also tried: .Not.Insert(), but that didn't work either.
I'd appreciate it if someone could help me out on this one.
I guess the property DocumentType is not really null when saving.
It seems there is an instance and without Cascade.All() on the reference it can not be saved.