I want to intercept all database query to add filters based on authorization info.
I implement the IDbCommandTreeInterceptor interface, but i don't known how to modify the tree query.
For example, i have the ClassA:
public class ClassA {
public int Id { get; set; }
public string Name { get; set; }
}
And now, i try to intercept all querys to filter all id's < 2
interceptor.Result.Where(classa = classa.Id < 2)
Is my idea correct? Is the IDbCommandTreeInterceptor interface the proper way to do this?
I don't found information about this interface in Internet.
Thanks
See the example that EF team member Rowan Miller presented at TechEd 2014. His example was SoftDeleteInterceptor (on GitHub) that changes a DELETE to an UPDATE of an IsDeleted flag on the entity.
Related
Challenge in EF6:
how to check Id of resulting row in the database after running this (esentially adding an entity record):
repository.Add(myEntity1);
...and use that id to add the second entity which has property X = to the id of the first entity?
use that id to add the second entity which has property X = to the id of the first entity?
repository.Add(myEntity2);
Right now there is no linkage between entity 1 and entity 2 because i don;t know how to save the id (automatically generated by ef) after first add
... and preserve it for adding it as a fk in the second entity?
Thanks a lot
You could try this following after your call to SaveChanges:
myEntity2.X = myEntity1.Id;
Then call SaveChanges again. This doesn't really utilise the power of Entity Framework, however, which is in managing relationships between entities. If your class was defined something like this:
public class MyEntity
{
[Key]
public int Id { get; set; }
[ForeignKey(nameof(RelatedEntity))]
public int RelatedEntityId { get; set; }
public MyEntity RelatedEntity { get; set; }
}
You could add your entities something like the following, and the Id/foreign key matching would be handled for you after calling SaveChanges:
myEntity1.RelatedEntity = myEntity2;
This is a fairly general solution, so if you'd like something more specific then you will need to include more details in your question.
You can read more about configuring Entity Framework relationships here.
I am trying to create an EF6 database where two tables, Addresses and Visits, share the same values as primary keys. Visits, conceptually, is an extension of Addresses. I'm splitting the tables because most of the records in Addresses don't require the fields contained in Visits.
I'm using the code first approach. Here's the relevant code for the Addresses:
public class Address
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int ID { get; set; }
[ForeignKey( "ID" )]
public virtual Visit Visit { get; set; }
and for Visits:
public class Visit
{
[Key]
[DatabaseGenerated( DatabaseGeneratedOption.Identity )]
public int ID { get; set; }
[ForeignKey("ID")]
public virtual Address Address { get; set; }
Based on my research, I also needed to include the following in my datacontext's OnModelCreating method:
modelBuilder.Entity<Visit>()
.HasOptional( v => v.Address )
.WithRequired();
Unfortunately, this doesn't work. I can update the database alright, after eliminating scaffolding calls to drop the primary index from Addresses (probably because the add-migration code thinks the primary key is "merely" a foreign key field). But when I run the application I get the following error:
Invalid column name 'Address_ID'.
Invalid column name 'Address_ID'.
From my limited experience with EF6 this looks like someplace deep inside the framework it's expecting there to be fields named 'Address_ID', probably in the Visits table (based on the 'table name'_'field name' naming structure I've seen for other implicitly added fields).
Is what I'm trying to do possible? If so, what am I missing in the configuration?
Additional Info
In trying out bubi's proposed solution, which unfortunately still generates the same error, that I could eliminate the OnModelCreating code and still get functional migration code generated.
Resolution
I finally did what I should've done earlier, which is examine the actual T-SQL code generated by the query which was blowing up. It turns out the problem was not in the Visit/Address linkage, but in a completely separate relationship involving another table. Apparently, somewhere along the way I did something to cause EF to think that other table (Voters) had an Address_ID foreign key field. In reality, the Address/Voter relationship should've been, and originally was, tied to a Voter.AddressID field.
Rather than try to unwind a large number of migrations I opted to blow away the database, blow away the migrations and start from scratch. After recreating the database -- but using bubi's suggestion -- I reloaded the data from backup and, voila, I was back in business.
For the sake of completeness, here's the code I ended up having to put into the OnModelCreating method call to get the Address/Visit relationship to work correctly:
modelBuilder.Entity<Visit>()
.HasRequired( v => v.Address )
.WithRequiredDependent( a => a.Visit );
modelBuilder.Entity<Address>()
.HasRequired( a => a.Visit )
.WithRequiredPrincipal( v => v.Address );
I am a little confused about why I have to use HasRequired in order to be able to use WithRequiredPrincipal/WithRequiredDependent, since not every entry in the Address table has an entry in the Visit table. That would seem to be "optional", not "required". But it appears to work, and maybe the "required" part is just internal to EF's model of the database, not the database itself.
There are 2 problems in the model:
- Only one of the Keys can be autonumbering, the other must get the same Id (this independently by EF).
- A mapping problem.
This model should work.
public class Address
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
public string Description { get; set; }
public virtual Visit Visit { get; set; }
}
public class Visit
{
public Visit()
{
Address = new Address();
}
[Key]
[ForeignKey("Address")]
public int Id { get; set; }
public string Description { get; set; }
public virtual Address Address { get; set; }
}
Example of use
var visit = new Visit
{
Description = "Visit",
Address = {Description = "AddressDescription"}
};
db.Visits.Add(visit);
db.SaveChanges();
In addition to what bubi mentioned, your modelBuilder statement contradicts the model in that it doesn't mention Address.Visit as the inverse property. So it thinks that the property represents a separate relationship and tries to create the Address_ID column for that relationship.
You need to have
modelBuilder.Entity<Visit>()
// from your description sounds like every Visit needs an Address
.HasRequired(v => v.Address )
// need to mention the inverse property here if you have one
.WithOptional(a => a.Visit);
...or just remove the statement completely since you're already using attributes, and EF should be able to figure it out by convention.
I am working on an N-tier application consisting of a UI layer (MVC), a Business Layer, a Domain layer (for the models) and a DAL for repositories and the EF DbContext.
I'm a bit confused about the inner workings of Entity Framework when updating the properties of an existing object and I'm looking for a good way to validate an object before updating its values in the database.
I have the following model:
public class BlogPost
{
public int BlogPostId { get; set; }
[Required]
public String Title { get; set; }
[Required]
public String Description { get; set; }
[Required]
public DateTime DateTime { get; set; }
public byte[] Image { get; set; }
}
I have the following methods in my manager in BL:
public BlogPost AddBlogPost(string title, string description, byte[] image = null)
{
BlogPost blogPost = new BlogPost()
{
Title = title,
Description = description,
DateTime = DateTime.Now
};
Validate(blogPost);
moduleRepository.CreateBlogPost(blogPost);
return blogPost;
}
public BlogPost ChangeBlogPost(BlogPost blogPost)
{
moduleRepository.UpdateBlogPost(blogPost);
return blogPost;
}
And I have the following methods in my DAL:
public BlogPost CreateBlogPost(BlogPost b)
{
b = context.BlogPosts.Add(b);
context.SaveChanges();
return b;
}
public BlogPost UpdateBlogPost(BlogPost b)
{
context.Entry(b).State = EntityState.Modified;
context.SaveChanges();
return b;
}
My question now is: what's a good way to check that the model is valid before actually trying to change its values in the database?
I was thinking something like this:
public BlogPost ChangeBlogPost(BlogPost blogPost)
{
// STEP 1: put the updated data in a new object
BlogPost updatedBlogPost = new BlogPost()
{
Title = blogPost.Title,
Description = blogPost.Description,
Image = blogPost.Image,
DateTime = blogPost.DateTime
};
// STEP 2: check if the model is valid
this.Validate(updatedBlogPost);
// STEP 3: read the existing blog post with that ID and change the properties
BlogPost b = moduleRepository.ReadBlogPost(blogPost.BlogPostId);
b.Title = blogPost.Title;
b.Description = blogPost.Description;
b.Image = blogPost.Image;
b.DateTime = blogPost.DateTime;
moduleRepository.UpdateBlogPost(blogPost);
return blogPost;
}
EDIT: I figured it's maybe better to just accept primitive types as parameter in the above method instead of the object.
I have a feeling that's too much work for a simple update, but I couldn't find anything else on the internet.
It's probably also worth noting that I'm using a singleton for the DbContext so I have to make sure Entity Framework doesn't change the values in the database before checking that those values are valid (since another call to the context by another class can cause SaveChanges()).
I know singleton on a DbContext is bad practice, but I saw no other option to avoid countless exceptions when working with multiple repositories and entities being tracked by multiple context instances.
PS: I also read about change tracking in Entity Framework but I'm not 100% sure how this will affect what I'm trying to do.
All suggestions and explanations are welcome.
Thanks in advance.
You would check ModelState.IsValid. There are a lot of validation mechanisms built into MVC that you can take advantage of. Built in attributes such as [Required] that you reference above, custom validators, making your business class implement IValidatableObject, overriding EF SaveChanges() to name a few. This article is a good start: https://msdn.microsoft.com/en-us/data/gg193959.aspx
Ok so I kinda answered my own question while doing some research and testing with some dummy data. I thought that when a property changed in MVC as a result of an Edit view, EF also tracked it and changed it in the database.
I figured out that's not how model binding works and realized after some fooling around that model binding actually creates a new object (instead of editing the properties of a dynamic proxy).
I guess I can now just validate the model and then just update the one with the same primary key in the database.
I'm using ASP.NET WebAPI and ran into a problem with a nested model that should be communicated via a WebAPI Controller:
The entities "bond, stock etc." each have a list of entities "price". Server-side, I use the following class to match this requirement..
public class Bond : BaseAsset
{
public int ID { get; set; }
public string Name { get; set; }
public virtual List<Price> Prices { get; set; }
}
This leads to the table "Price" having a column for bond, stock etc. and, in case a price is attached to a bond, an entry in its column for bond foreign key.
The error I initially got was
There is already an open DataReader associated with this Command
I fixed that by altering the Connection String to allow MultipleActiveResultSets.
However, I feel there must be better options or at least alternatives when handling nested models. Is it, e.g., a sign for bad model design when one runs into such a problem? Would eager loading change anything?
One alternative to mars is to disable lazy loading
In your DbContext
Configuration.LazyLoadingEnabled = false;
plus when you are loading your data you can explicit load your child tables
context.Bonds.Include(b => b.Prices)
Table name: TableStatus The tool produces TableStatu with a variable name of TableStatus. For others, TablePerson it creates TablePerson with variable name TablePersons. With Code First you can remove the pluralizations. I found some snippets for both the Entity.tt and Context.tt to remove/add pluralization when you reverse engineer, but neither seem to have any affect on the output classes and DbContext DbSet names. It may be something simple, but I don't see it.
When you do a database-first model, there is an option to pluralize/singularize entity names. Turn this off and it should solve your problem.
You can use the Table attribute to specify the table name.
[Table("account", Schema = "dbo")]
public class Account
{
[Key]
public int id { get; set; }
public string Email { get; set; }
}