I am building a relatively simple webapp, but have run into a bit of a problem. After having searched low and high, I can't seem to find anyone with similar issues.
So the situation:
I have an entity:
public class Entity
{
[Key]
public int EntityId { get; set;}
public string EntityName { get; set; }
public virtual ICollection<OtherEntity> OtherEntities { get; set; }
}
Reason for the virtual ICollection<OtherEntity> is a many to many relationship between the two.
My DbContext:
public class WebAppDB : IdentityDbContext<ApplicationUser>
{
public DbSet<Entity> Entities{ get; set; }
public WebAppDB () : base("DefaultConnection")
{
}
public static WebAppDB Create()
{
return new WebAppDB();
}
}
}
The default connection goes to an Amazon RDS SQL Server Express.
Around this I have created a repository:
public interface IEntityRepository
{
IQueryable<Entity> AlEntitiss { get; }
IQueryable<Entity> AllEntitissIncluding(params Expression<Func<Entity, object>>[] includeProperties);
Entity FindEntity(int id);
void InsertOrUpdateEntity(Entity entity);
void DeleteEntity(int id);
void Save();
}
public class EntityRepository : IEntityRepository
{
// handle to the database through the O.R.M. system.
private WebAppDB context = new WebAppDB();
public IQueryable<Entity> AllCEntitys
{
get { return context.Entitiss; }
}
public IQueryable<Entity> AllClassesIncluding(params Expression<Func<Entity, object>>[] includeProperties)
{
IQueryable<Entity> query = context.Entitiss;
foreach (var includeProperty in includeProperties)
{
query = query.Include(includeProperty);
}
return query;
}
public Entity FindEntity(int id)
{
return context.Entitiss.Find(id);
}
public void InsertOrUpdateEntity(Entity Entity)
{
if (Entity.EntityId == 0)
{
context.Entitiss.Add(Entity);
}
else
{
context.Entry(Entity).State = EntityState.Modified;
}
}
public void DeleteEntity(int id)
{
Entity Entity = FindEntity(id);
context.Entitys.Remove(Entity);
}
public void Save()
{
context.SaveChanges();
}
}
Now, the problem lies in the fact that I can get a list of the entities I have in the database and load them just fine into Selectlists or similar structures.
I can also get specific Entities based on other properties than the primary key.
But I can't get a single entity from the database using the primary key as my entry point. I have tried using DbSet.Entities.SingleOrDefault(), .Single(), .Find()
I have also tried to retrieve it using
DbSet.Entities.ToList().Where(x => x.EntityId == id)
I have moved from 2 data contexts down to 1, I have checked that I am referencing the same version of the EF in all projects in the solution (have a separate project for the entities).
After having read This, I fiddled with the Lazy loading, but no effect.
So I am running out of ideas and places to look.
If you need more information I will provide it to the best of my ability.
Thank you for reading and helping.
Update1:
I have tried moving to a local database with no luck, and it seems what I earlier described with loading lists of Entities working was exaggerated. They too don't load consistently when called.
Update 2:
Having used the SQL profiler to determine that not all calls from the controllers where executed on the database, I tried transplanting the entities to a fresh MVC project. Unfortunately the problem persists and I am out of ideas as this point.
Update 3:
After some more investigation and some help from Gert Arnold it has turned out that I misdiagnosed the initial problem. Due to poor coding practices it was not 1 central problem, but several separate problems all exhibiting similar characteristics that led me to the wrong conclusion that the EF was at fault. I am sorry to have wasted anyones time with this.
public Class FindEntity(int id)
{
//Want to find a specific student
return context.Entitys.Find(id);
}
This one seems a bit weird to me, what's the Class? I think it should be Student. Anyway, check out the code sample below:
public Entity FindEntity(int id)
{
return context.Entities.FirstOrDefault(e => e.EntityId == id); // note that it will return null if not found.
}
Related
I need to remove all records in a given table, using a DbContext in Entity Framework. I need this to be portable, so it can't rely on SQL statements or stored procedures. I've looked through the answers to this question, but none of them meet my requirements or are ideal solutions for a variety of reasons.
I could use the RemoveRange method, i.e.
DbContext.Table.RemoveRange(all);
But this doesn't scale well, because it selects all entries before deleting, which could take a long, long time with Entity Framework. Iterating through each record and removing them individually with Remove(record) has the same problem.
Using SQL this is simple, using a TRUNCATE command. Even a simple DELETE FROM [TableName] command works, but I don't know how scalable that is.
Is there any solution that uses only Entity Framework (no SQL), and doesn't require selecting all records first before deleting them?
This is currently not something that is possible using Entity Framework. see https://github.com/dotnet/efcore/issues/795
There may be an extension out there that will allow you to do that, but I am not sure it will work will all RDBMS systems.
Let's suppose you have BrandData table with records about some brands:
public class BrandData
{
[Key]
public int Id { get; set; }
public string Name { get; set; }
public string Description { get; set; }
}
Also you've created a dbcontext:
public class MyDbContext : DbContext
{
public MyDbContext(DbContextOptions<MyDbContext> options) : base(options)
{
Database.Migrate();
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<BrandData>().HasData(new BrandData { Id = 999, Name = "LG", Description = "TV brand" });
}
public DbSet<BrandData> BrandData { get; set; }
}
Finally, this is the method that deletes brand by its ID:
public async Task DeleteModelAsync(int id)
{
var data = _dbContext.ModelData.FirstOrDefault(b => b.Id == id);
if (data != null)
{
_dbContext.ModelData.Remove(data);
await _dbContext.SaveChangesAsync();
}
}
Changes will be done after SaveChangesAsync() method run.
UPDATE
To delete all records:
var brands = await _dbContext.BrandData.ToListAsync();
foreach(var brand in brands)
{
_dbContext.BrandData.Remove(brand);
}
await _dbContext.SaveChangesAsync();
I'm trying to implement Soft Delete in a .NET Core 1.1.* Web App, backed by Entity Framework Core 1.1.*. I'm using Sql Server as my DB.
Migrating to .NET core 2.* is not an option at the moment.
After reading books, tuts and 3ds, I've implemented this feature using a Discriminator column. The deletion procedure is apparently working as expected. What's wrong is the data retrieval: deleted entities are still shown within my EF query results.
Current situation
Here's some C# code. I'll keep things as simple as possible
The interfaces:
// Soft deletion interface
public intercace ISoftDeletable
{}
// Another interface for some shadow properties
public interface IEntity
{}
The base class:
public abstract class Entity : IEntity, ISoftDeletable
{
public int MyBaseProp { get; set; }
}
One of my derived classes:
public class MyDerivedEntity: Entity
{
public string Name { get; set; }
public IList<MyChildEntity> Children { get; set; }
}
public class MyChildEntity: Entity
{
public string MyChildProp { get; set; }
}
The Context
public class MyContext: DbContext
{
public MyContext(DbContextOptions<MyContext> options)
: base(options)
{ }
public DbSet<MyDerivedEntity> EntitiesToUse { get; set; }
protected override void OnModelCreating(ModelBuilder builder)
{
foreach (var entity in builder.Model.GetEntityTypes())
{
if (typeof(IEntity).IsAssignableFrom(entity.ClrType))
{
builder.Entity(entity.ClrType).Property<string>("MyShadowProperty");
}
if (typeof(ISoftDeletable).IsAssignableFrom(entity.ClrType))
{
// Discriminator column
builder.Entity(entity.ClrType).HasDiscriminator("IsDeleted", typeof(bool)).HasValue(false);
// Shadow Property
builder.Entity(entity.ClrType).Property(typeof(bool), "IsDeleted").IsRequired(true).HasDefaultValue(false);
builder.Entity(entity.ClrType).Property(typeof(bool), "IsDeleted").Metadata.IsReadOnlyAfterSave = false;
}
}
// Other model configurations
base.OnModelCreating(builder);
}
// SaveChangesAsync are almost the same
public override int SaveChanges()
{
AuditEntities();
return base.SaveChanges();
}
private void AuditEntities()
{
foreach (EntityEntry<IEntity> entry in ChangeTracker.Entries<IEntity>())
{
// do something with MyShadowProperty...
}
foreach (EntityEntry<ISoftDeletable> entry in changeTracker.Entries<ISoftDeletable>().Where(w => w.State == EntityState.Deleted))
{
// Set the entity as Softly Deleted
entry.Property("IsDeleted").CurrentValue = true;
// Ensure the entity state is modified to prevend hard deletion
entry.State = EntityState.Modified;
}
}
}
The Problem
Everything works as expected, except the data retrieval.
Here's a sample call:
var results = await _context.EntitiesToUse.Include(e => e.SomeChildEntity).AsNoTracking();
I expect the results to include only available myDerivedEntities with .IsDeleted == false. The problem is that my deleted entities are not filtered out. Why?
Please, what's wrong with my code? Am I missing something?
Thank you all so much!
Entity Framework Core 2.0 supports Global Query Filter
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<ISoftDeletable>().HasQueryFilter(e => !e.IsDeleted);
base.OnModelCreating(modelBuilder);
}
You can find more info and examples here
I recommend you the built-in EF Core Global Query Filter but in some situations, Entity Framework Plus could also help.
Disclaimer: I'm the owner of this project
EF+ Query Filter allows you to filter DbSet Globally and by Instance.
// using Z.EntityFramework.Plus; // Don't forget to include this.
var ctx = new EntitiesContext();
ctx.Filter<IUser>(q => q.Where(x => !x.IsSystemUser ));
// SELECT * FROM Customers WHERE IsSystemUser = FALSE
var list = ctx.Customers.ToList();
Wiki: EF+ Query Filter
EDIT: Answer sub-question
Please, Is your library compatible with EF Core 1.1
Yes, it should be compatible with .NET Standard 1.3
In our WebApi project we use EF CodeFirst approach. Also we use 2 types of databases: SQL Server and MySQL. All tables have the field ID, but in SQL Server database this field has int data type, in MySQL database this field is char(36) and contains GUID.
To solve the problem I created a custom value type like IdType and changed all model classes to use that type insted int:
public class Document
{
public IdType ID { get; set; }
public string DocumentNm { get; set; }
...
}
Then I configured the DbContext (e.g for SQL Server)
modelBuilder.Properties<IdType>().Configure(c => c.HasColumnType("int"));
...and changed repository:
public interface IRepository<T> where T : IEntity
{
IQueryable<T> GetAll();
T GetById(IdType id);
...
}
After that, when I try to go to e.g. http://localhost:7081/api/Document, it gives me an error:
Multiple actions were found that match the request: \r\nGet on type
WebUI.Controllers.API.DocumentController\r\nGetById on type
WebUI.Controllers.API.DocumentController
I use default settings of routing. Here is [HttpGet] methods from DocumentController:
public HttpResponseMessage Get() { ... }
public HttpResponseMessage GetById(IdType id) { ... }
How can I solve the problem? Could this be the cause of incorrect implementation of IdType?
P.S. I created IdType for int values as described here. if I have to add more informations, please let me know.
UPDATE
DocumentController:
public HttpResponseMessage GetById(IdType id)
{
var entity = repository.GetById(id);
if (entity == null)
{
return ErrorMsg(HttpStatusCode.NotFound, string.Format("No {0} with ID = {1}", GenericTypeName, id););
}
return Request.CreateResponse(HttpStatusCode.OK, entity);
}
My repository:
public virtual T GetById(IdType id)
{
return GetAll().FirstOrDefault(x => x.ID == id);
}
public virtual IQueryable<T> GetAll()
{
return entities = context.Set<T>();
}
It seems that it not implemented yet in current version of Entity Framework
And as mentioned in task on GitHub
we're currently planning to work on lighting this feature up after our
initial RTM of EF7.
Well, I have the following model structure: I have one class - DatabaseEntity which is basically
public class DatabaseEntity
{
public int Id { get; set; }
}
so each entity like product, category etc will inherit DatabaseEntity and have Id property. Also I have typical EntityFramework repository class with InsertOrUpdate method:
private readonly DbContext _database;
public void InsertOrUpdate<TObject>(TObject entity) where TObject : DatabaseEntity
{
if(entity.Id == default(int))
{
// New entity
DbSet<TObject>().Add(entity);
}
else
{
// Existing entity
_database.Entry(entity).State = EntityState.Modified;
}
_database.SaveChanges();
}
Then I download from eBay via eBay api list of categoies I have to add to database. Basically category is:
public class EbayCategory : DatabaseEntity
{
// It has Id since it inherits DatabaseEntity
public string Name { get; set; }
// ... some other properties
}
But, the problem is, when I download those categories I download and their Id properties, which, of course, already have values. And when I try to save them to database like:
public void UpdateCategories(IEnumerable<EbayCategory> newCategories)
{
foreach (var newCategory in newCategories)
{
_repository.InsertOrUpdate(newCategory);
}
}
I face some issues... First of all, entity.Id != default(int) because it has value, so repository tries to update this entity, instead of adding, but it is not in the database or context so it throws the following exception:
System.Data.Entity.Infrastructure.DbUpdateConcurencyException
"Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. Refresh ObjectStateManager entries."
... because it thinks that someone else deleted entity which I am trying to update. How can I save this InsertOrUpdate logic, since a lot of projects are based on it, and be able to add items (EbayCategories) with primary key (Id) to database and then update/delete them like other entities without discarding EbayCategory.Id value?
To allow you to manually generate Ids you need a class that has a manually generated ID - so it cannot inherit from DatabaseEntity
public class EbayCategory
{
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int Id { get; set; }
public string Name { get; set; }
// ... some other properties
}
Now you will need a different InsertOrUpdate to handle entities that have manually generated keys:
public void InsertOrUpdate(EbayCategory entity)
{
if(Find(entity.ID == null)
{
// New entity
DbSet<EbayCategory>().Add(entity);
}
else
{
// Existing entity
_database.Entry(entity).State = EntityState.Modified;
}
_database.SaveChanges();
}
Colin's answer above quite correctly shows how to achieve this setting using data annotations.
But in the presented problem the entity is a subclass so you can't add the annotation without changing the entity class.
There is an alternative configuration method: Fluent Configuration. Here's my example using an EntityTypeConfiguration class:
public class LookupSchoolsConfiguration : EntityTypeConfiguration<LookupSchools>
{
public LookupSchoolsConfiguration()
{
Property(l => l.Id).HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);
}
}
You can also add configuration directly to the modelBuilder as per this post: https://stackoverflow.com/a/4999894/486028
I have my Database Context:
public class ProductContext : DbContext
{
public ProductContext() : base ("DefaultConnection") {}
public DbSet<Product> Products {get;set;}
}
and my Repository:
public class ProductRepository : IProductRepository
{
private ProductContext _dbContext = new ProductContext();
public IQueryable<Product> Products { get { return _dbContext.Products; } }
}
when I query my database in the Edit Action:
public ActionResult Edit(Guid id)
{
var item = _repository.Products.FirstOrDefault(x => x.Id.Equals(id));
return View(item);
}
I would usually use a ViewModel but this is purely to show the scenario.
When I query the database using the var item line, does EntityFramework change the state of that item.
Can I pass around that item through a multitude of Services in the Service Layer and then finally save it using my method:
public void SaveEntity<TEntity>(TEntity entityToSave) where TEntity : DbEntity
{
if (entityToSave.Id.Equals(Guid.Empty))
_dbContext.Set<TEntity>().Add(entityToSave);
else
_dbContext.Entry<TEntity>(entityToSave).State = EntityState.Modified;
_dbContext.SaveChanges();
}
It won't throw an exception saying that there is already a Entity with the same Id as the one you're trying to Save?
So after trial and error, it seems that this works perfectly fine, and it doesn't bring back any errors. There is one thing to look out for:
This navigation property:
public virtual Category Category { get;set; }
public Guid CategoryId { get;set; }
That could reside in the Product model has a little gotcha, that is:
When editing or saving a new Product, you should only set the CategoryId and not just the Category exclusively because you will get duplicate Category entries every time you edit or save if you use the a Category that already exist within the database...
I think you should the navigation property solely for your ease, not for use when modifying entities...