I'm using AutoMapper to map a lot of Entity models to View Model that I use in my controllers and views (.Net MVC)
There is a lot of relations in the DB and so our VM have a lot of childs (who have childs, and so and so)
public class InvoiceVMFull : VMBase
{
public int Id { get; set; }
public InvoiceType InvoiceType { get; set; }
public string Reference { get; set; }
//.... shortened code for readability
// list all entity fields
public List<string> InvoiceMainAddress { get; set; }
public List<string> InvoiceDlvAddress { get; set; }
}
It works just fine, but is very slow and always load from the DB all relations whereas I usually need only a few datas...
So I created some light VM that I want to use for the majority of our pages.
public class InvoiceVMLite : VMBase
{
public int Id { get; set; }
public string Reference { get; set; }
//.... shortened code for readability
// list only some of the entity fields (most used)
public StoredFileVM InvoiceFile { get; set; }
}
The problem is I can't find how :
to map one Entity object to the two VMs and how to choose the right one (to load from DB) using the context (the page or event called)
to map two VMs to one entity and save (on the DB) only the fields that are present in the VM used and don't erase the absent ones
I tried to create the mapping both VM :
Mapper.CreateMap<Invoice, InvoiceVMLite>();
Mapper.CreateMap<Invoice, InvoiceVMFull>();
But when I try to call the mapping for Lite, it doesn't exist (have been overridden by Full) :
Mapper.Map(invoice, InvoiceEntity, InvoiceVMLite)
Correct Use of Map function
It looks like you are calling map incorrectly. Try these instead
var vmLite = Mapper.Map<Invoice, InvoiceVMLite>(invoice);
var vmFull = Mapper.Map<Invoice, InvoiceVMFull>(invoice);
var vmLite = Mapper.Map(invoice); // would work if it were not ambiguous what the destination was based on the input.
Entity to two view models
You would usually create two mappings, one for each view model from the one entity. I'd suggest the cleanest is to have two separate views (separate Actions in a controller) for each view model. This may involve a quick redirect after you've decided on context which one to use.
View models to entity
Automapper is not meant for mapping from view models to Entities for many reasons, including the challenge you'd face. Instead you would pass specific parameters. The author of Automapper, Jimmy Bogard, wrote a good article on why this is the case.
I couldnt manage to do that with AutoMapper, and so I created my own convert methods (Entity <=> VM) with a lot of reflexivity, and with specific cases handled in each of the VM classes.
Now I can easily get a full or lite VM from an Entity, and also specify the depth in relation I want to go. So it's A LOT faster and more adaptable than AutoMapper
And I can save a VM to an entity (only saving modified fields if I want) that I create or that i got from base. So it's A LOT faster and adaptable than AutoMapper
In conclusion : Don't use autoMapper, it seem easy but create so many performance issues that it isn't worth it
Related
I`m in process of learning C# & .NET and EF (with aspnetboilerplate) and I came up with idea to create some dummy project so I can practice. But last 4 hour Im stuck with this error and hope someone here can help me.
What I create( well at least I think I create it correctly ) is 2 class called "Ingredient" and "Master"
I want to use it for categorize Ingredient with "Master" class.
For example ingredient like
Chicken breast
chicken drumstick
Both of them belong to Meat ( witch is input in "Master" database ) and here is my code
Ingredient.cs
public class Ingrident : Entity
{
public string Name { get; set; }
public Master Master { get; set; }
public int MasterId { get; set; }
}
Master.cs
public class Master : Entity
{
public string Name { get; set; }
public List<Ingrident> Ingridents { get; set; } = new();
}
IngridientAppService.cs
public List<IngridientDto> GetIngWithParent()
{
var result = _ingRepository.GetAllIncluding(x => x.Master);
//Also I try this but doesn`t work
// var result = _ingRepository.GetAll().Where(x => x.MasterId == x.Master.Id);
return ObjectMapper.Map<List<IngridientDto>>(result);
}
IngridientDto.cs
[AutoMap(typeof(IndexIngrident.Entities.Ingrident))]
public class IngridientDto : EntityDto
{
public string Name { get; set; }
public List<MasterDto> Master { get; set; }
public int MasterId { get; set; }
}
MasterDto.cs
[AutoMap(typeof(IndexIngrident.Entities.Master))]
public class MasterDto : EntityDto
{
public string Name { get; set; }
}
When I created ( for last practice ) M -> M relationship this approach with .getAllIncluding work but now when I have One -> Many it won`t work.
Hope someone will be able to help me or at least give me some good hint.
Have a nice day !
Straight up the examples you are probably referring to (regarding the repository etc.) are overcomplicated and for most cases, not what you'd want to implement.
The first issue I see is that while your entities are set up for a 1-to-many relationship from Master to Ingredients, your DTOs are set up from Ingredient to Masters which definitely won't map properly.
Start with the simplest thing. Get rid of the Repository and get rid of the DTOs. I'm not sure what the base class "Entity" does, but I'm guessing it exposes a common key property called "Id". For starters I'd probably ditch that as well. When it comes to primary keys there are typically two naming approaches, every table uses a PK called "Id", or each table uses a PK with the TableName suffixed with "Id". I.e. "Id" vs. "IngredientId". Personally I find the second option makes it very clear when pairing FKs and PKs given they'd have the same name.
When it comes to representing relationships through navigation properties one important detail is ensuring navigation properties are linked to their respective FK properties if present, or better, use shadow properties for the FKs.
For example with your Ingredient table, getting rid of the Entity base class:
[Table("Ingredients")]
public class Ingredient : Entity
{
[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int IngredientId { get; set; }
public string Name { get; set; }
public int MasterId { get; set; }
[ForeignKey("MasterId")]
public virtual Master Master { get; set; }
}
This example uses EF attributes to aid in telling EF how to resolve the entity properties to respective tables and columns, as well as the relationship between Ingredient and Master. EF can work much of this out by convention, but it's good to understand and apply it explicitly because eventually you will come across situations where convention doesn't work as you expect.
Identifying the (Primary)Key and indicating it is an Identity column also tells EF to expect that the database will populate the PK automatically. (Highly recommended)
On the Master side we do something similar:
[Table("Masters")]
public class Master : Entity
{
[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int MasterId { get; set; }
public string Name { get; set; }
[InverseProperty("Master")]
public virtual ICollection<Ingredient> Ingredients { get; set; } = new List<Ingredient>();
}
Again we denote the Primary Key, and for our Ingredients collection, we tell EF what property on the other side (Ingredient) it should use to associate to this Master's list of Ingredients using the InverseProperty attribute.
Attributes are just one option to set up the relationships etc. The other options are to use configuration classes that implement IEntityConfiguration<TEntity> (EF Core), or to configure them as part of the OnModelCreating event in the DbContext. That last option I would only recommend for very small projects as it can start to become a bit of a God method quickly. You can split it up into calls to various private methods, but you may as well just use IEntityConfiguration classes then.
Now when you go to fetch Ingredients with it's Master, or a Master with its Ingredients:
using (var context = new AppDbContext())
{
var ingredients = context.Ingredients
.Include(x => x.Master)
.Where(x => x.Master.Name.Contains("chicken"))
.ToList();
// or
var masters = context.Master
.Include(x => x.Ingredients)
.Where(x => x.Name.Contains("chicken"))
.ToList();
// ...
}
Repository patterns are a more advanced concept that have a few good reasons to implement, but for the most part they are not necessary and an anti-pattern within EF implementations. I consider Generic repositories to always be an anti-pattern for EF implementations. I.e. Repository<Ingredient> The main reason not to use repositories, especially Generic repositories with EF is that you are automatically increasing the complexity of your implementation and/or crippling the capabilities that EF can bring to your solution. As you see from working with your example, simply getting across an eager load through to the repository means writing in complex Expression<Func<TEntity>> parameters, and that just covers eager loading. Supporting projection, pagination, sorting, etc. adds even more boiler-plate complexity or limits your solution and performance without these capabilities that EF can provide out of the box.
Some good reasons to consider studying up on repository implementations /w EF:
Facilitate unit testing. (Repositories are easier to mock than DbContexts/DbSets)
Centralizing low-level data rules such as tenancy, soft deletes, and authorization.
Some bad (albeit very common) reasons to consider repositories:
Abstracting code from references or knowledge of the dependency on EF.
Abstracting the code so that EF could be substituted out.
Projecting to DTOs or ViewModels is an important aspect to building efficient and secure solutions with EF. It's not clear what "ObjectMapper" is, whether it is an Automapper Mapper instance or something else. I would highly recommend starting to grasp projection by using Linq's Select syntax to fill in a desired DTO from the models. The first key difference when using Projection properly is that when you project an object graph, you do not need to worry about eager loading related entities. Any related entity / property referenced in your projection (Select) will automatically be loaded as necessary. Later, if you want to leverage a tool like Automapper to help remove the clutter of Select statements, you will want to configure your mapping configuration then use Automapper's ProjectTo method rather than Map. ProjectTo works with EF's IQueryable implementation to resolve your mapping down to the SQL just like Select does, where Map would need to return everything eager loaded in order to populate related data. ProjectTo and Select can result in more efficient queries that can better take advantage of indexing than Eager Loading entire object graphs. (Less data over the wire between database and server/app) Map is still very useful such as scenarios where you want to copy values back from a DTO into a loaded entity.
Do it like this
public class Ingrident:Entity
{
public string Name { get; set; }
[ForeignKey(nameof(MasterId))]
public Master Master { get; set; }
public int MasterId { get; set; }
}
I have 2 tables that saved family members, when I use include to retrieve the family members, the generated T-SQL is what I'm expected, but when I see the result from VS, like image below, it's look like never ending.
My questions:
It's this normal?
Should I avoid include when the relationship becomes complex?
If it is normal, will this very memory consumption?
POCO
public class Cust_ProfileTbl
{
[Key]
public long bintAccountNo { get; set; }
public string nvarCardName { get; set; }
public string varEmail { get; set; }
public virtual ICollection<Cust_ProfileFamilyTbl> profileFamilyParents { get; set; }
public virtual ICollection<Cust_ProfileFamilyTbl> profileFamilyChildren { get; set; }
}
public class Cust_ProfileFamilyTbl
{
[Key]
public int intProfileFamily { get; set; }
public long bintAccountNo { get; set; }
public long bintAccountNoMember { get; set; }
public virtual Cust_ProfileTbl custProfileParent { get; set; }
public virtual Cust_ProfileTbl custProfileChild { get; set; }
}
LINQ
var rs = from family in context.member.Include("profileFamilyParents.custProfileChild")
select family;
rs = rs.Where(x => x.bintAccountNo.Equals(1));
var result = rs.ToList();
In onModelCreating
modelBuilder.Entity<Cust_ProfileFamilyTbl>()
.HasRequired(m => m.custProfileParent)
.WithMany(t => t.profileFamilyParents)
.HasForeignKey(m => m.bintAccountNo)
.WillCascadeOnDelete(false);
modelBuilder.Entity<Cust_ProfileFamilyTbl>()
.HasRequired(m => m.custProfileChild)
.WithMany(t => t.profileFamilyChildren)
.HasForeignKey(m => m.bintAccountNoMember)
.WillCascadeOnDelete(false);
When people use an ORM like EF in their application, many times the application design gets driven by this ORM and the entities defined in its model. When the app is a simple "CRUD" application, that's not a problem, but an advantage, because you spare a lot of time.
However when things start to get more complicated, an "ORM guided design" becomes a problem. This looks to be the case.
There are at least two problems, recovered from the comments:
the data retrieved from the DB is more than needed
in this case, because of some particular relationships between entities, there is a circular reference, which creates an endless loop and a stack overflow when trying to show the model in the view
When this kind of situation shows up, the most advisable is to break the tight tie between the ORM and the rest of the app, which can be dine by defining a new class, and projecting the data into it. Let's give a generic ProfileDto name.
public class ProfileDto { ... }
DTO is a generic name for this kind of classes: Data Transfer Objects - but, when they have specific purposes, they can get other names like view models, when they're going to be used as the model sent to an MVC view
And then, what you need to do is to project the result of the query into the DTO:
var model = theQuery.Select(i => new ProfileDto { a = i.a, b = i.b...}).ToList();
With a good design of the Dto you'll only recover the needed data from the DB, and you'll avoid the loop problem (by not including the navigation property that creates the loop).
NOTE: many times people uses mappers, like AutoMapper or ValueInjecter to make the mapping, or part of the mapping, automatic
Code standardization is a very good idea until it becomes a source of problems. The main purpose of writing code is implementing the business logic. If code standardization, technology, or whatever, makes it harder to implement business logic, instead of contributing to the solution, they become a problem, so you need to avoid them.
Mapping you created is Normal but use of Include depends upon its usage
Use of Include depends on situation of use for example if you want to cache it in memory then you may use include, Where as if you are using only showing properties of Cust_ProfileTbl
class in some grid and on click you want show details of Cust_ProfileFamilyTbl then you might don't want to use include. But be careful if you are using Automapper or something because when It will try to map related properties it will query database.
It will consume memeory when you execute ToList() as doing so you are Loading query result into List collection. Where as If you again want to query the result then you can use ToQueryable() or just want to iterate the you can don't load them to List.
I'm using Entity Framework 6.0.2 to map some simple hand-coded models to an existing database structure. The primary model at the moment is:
public class Occurrence
{
public int ID { get; set; }
public Guid LegacyID { get; set; }
public string Note { get; set; }
public virtual ICollection<OccurrenceHistory> History { get; set; }
}
(The OccurrenceHistory model isn't really relevant to this, but that part is working fine whereby EF loads up the child records for this model.)
The mapping is simple, and I try to be as explicit as I can be (since as the application grows there will be some less-intuitive mapping):
public class OccurrenceMap : EntityTypeConfiguration<Occurrence>
{
public OccurrenceMap()
{
ToTable("Occurrence");
HasKey(o => o.ID);
Property(o => o.ID).IsRequired().HasColumnName("ID");
Property(o => o.LegacyID).IsRequired().HasColumnName("LegacyID");
Property(o => o.Note).IsUnicode().IsOptional().HasColumnName("Note");
}
}
But if I add a private property to the model, EF tries to map it to the database. Something like this:
private OccurrenceHistory CurrentHistory { get; set; }
(Internal to the model I would have some logic for maintaining that field, for other private operations.) When EF generates a SELECT statement it ends up looking for a column called CurrentHistory_ID which of course doesn't exist.
I can make the property public and set the mapping to ignore it:
Ignore(o => o.CurrentHistory);
But I don't want the property to be public. The model is going to internally track some information which the application code shouldn't see.
Is there a way to tell EF to just ignore any and all private members? Even if it's on a per-map basis? I'd particularly like to do this without having to add EF data annotations to the models themselves, since that would not only be a bit of a leaky abstraction (persistence-ignorant models would then have persistence information on them) but it would also mean that the domain core assembly which holds the models would carry a reference to EntityFramework.dll everywhere it goes, which isn't ideal.
A colleague pointed me to a blog post that led to a very practical approach.
So what I have is a private property:
private OccurrenceHistory CurrentHistory { get; set; }
The core of the problem is that I can't use that in my mapping:
Ignore(o => o.CurrentHistory);
Because, clearly, the property is private and can't be accessed in this context. What the blog post suggests is exposing a public static expression which references the private property:
private OccurrenceHistory CurrentHistory { get; set; }
public static readonly Expression<Func<Occurrence, OccurrenceHistory>> CurrentHistoryExpression = o => o.CurrentHistory;
I can then reference that in the mapping:
Ignore(Occurrence.CurrentHistoryExpression);
As with anything, it's a mix of pros and cons. But in this case I think the pros far outweigh the cons.
Pros:
The domain core assembly doesn't need to carry a reference to EntityFramework.dll.
The persistence mapping is entirely encapsulated within the DAL assembly.
Cons:
Models need to expose a little information about their inner workings.
The con breaks encapsulation, but only slightly. Consuming code still can't access that property or its value on instances, it can only see that the property exists statically. Which, really, isn't a big deal, since developers can see it anyway. I feel that the spirit of encapsulation is still preserved on any given instance of the model.
I would like to setup my mongo db poco models so that they automatically retreive their foreign documents, similarly to how its handled by EF and nhibernate.
This is the solution that I have come up with so far, its a bit clunky but the best that I could manage:
Basic model:
public class DocumentOwner
{
public virtual ObjectId OwnerID { get; set; }
}
Extended model with manual retrieval of foreign documents:
public class DocumentOwner
{
public MongoDatabase DB { get; set; }
public virtual ObjectId OwnerID { get; set; }
public virtual Individual Owner
{
get
{
return this.DB.GetCollection<Individual>().FindOne(Query<Individual>.EQ(x => x.Id, this.OwnerID));
}
}
The main problem with this solution is that I have to manually inject the mongo database instance which is quite clunky, if there was a way to use ninject to inject this instance that would be a lot tidier. Even better if somehow I could use MongoDBRef to retrieve the individual without having to perform a manual query...
You probably want some sort of repository class that owns the MongoDatabase object instead, & have it insert the returned document into your class. Saving changes might be awkward because you'd need to get document back out. If so, then maybe having the Mongo class in the object is the right thing. Either way a repository class would help.
I'd use a binding to a Func, something like Func<MongoDatabase, DocumentOwner> within the service to create new instances.
I am looking into migrate a large project to Entity Framework 4.0 but am not sure if it can handle my inheritance scenario.
I have several projects that inherit from an object in the “main” project. Here is a sample base class:
namespace People
{
public class Person
{
public int age { get; set; }
public String firstName { get; set; }
public String lastName { get; set; }
}
}
and one of the sub-classes:
namespace People.LawEnforcement
{
public class PoliceOfficer : People.Person
{
public string badgeNumber { get; set; }
public string precinct { get; set; }
}
}
And this is what the project layout looks like:
People - People.Education - People.LawEnforcement http://img51.imageshack.us/img51/7293/efdemo.png
Some customers of the application will use classes from the People.LawEnforcement and other users will use People.Education and some will use both. I only ship the assembles that the users will need. So the Assembles act somewhat like plug-ins in that they add features to the core app.
Is there anyway in Entity Framework to support this scenario?
Based on this SO question I'm think something like this might work:
ctx.MetadataWorkspace.LoadFromAssembly(typeof(PoliceOfficer).Assembly);
But even if that works then it seams as if my EDMX file will need to know about all the projects. I would rather have each project contain the metadata for the classes in that project but I'm not sure if that is possible.
If this isn't possible with entity framework is there another solution (NHibernate, Active Record, etc.) that would work?
Yes this is possible, using the LoadFromAssembly(..) method you've already found.
... but it will only work if you have an specialized model (i.e. EDMX) for each distinct type of client application.
This is because EF (and most other ORMs) require a class for each entity in the model, so if some clients don't know about some classes, you will need a model without the corresponding entities -- i.e. a customized EDMX for each scenario.
To make it easier to create a new model for each client application, if I was you I'd use Code-Only following the best practices laid out on my blog, to make it easy to grab only the fragments of the model you need actually need.
Hope this helps
Alex
Alex is correct (+1), but I'd strongly urge you to reconsider your model. In the real world, a police officer is not a subtype of a person. Rather, it's an attribute of that person's employment. I think programmers frequently tend to over-emphasize inheritance at the expense of composition in object oriented design, but it's especially problematic in O/R mapping. Remember that an object instance can only ever have one type. When that object is stored in the database, the instance can only have that type for as long as it exists, across multiple application sessions. What if a person had two jobs, as a police officer and a teacher? Perhaps that scenario is unlikely, but the general problem is more common than you might expect.
More relevant to your question, I think you can solve your actual problem at hand by making your mapped entity model more generic, and your application-specific data projections on the entities rather than entities themselves. Consider entities like:
public class JobType
{
public Guid Id { get; set; }
// ...
}
public class Job
{
public JobType JobType { get; set; }
public string EmployeeNumber { get; set; }
}
public class Person
{
public EntityCollection<Job> Jobs { get; set; }
}
Now your law enforcement app can do:
var po = from p in Context.People
let poJob = p.Jobs.Where(j => j.JobType == JobType.PoliceOfficerId).FirstOrDefault()
where poJob != null
select new PoliceOfficer
{
Id = p.Id,
BadgeNumber = poJob.EmployeeNumber
};
Where PoliceOfficer is just a POCO, not a mapped entity of any kind.
And with that you've achieved your goal of having a common data model, but having the "job type specific" elements in separate projects.