In EF 4, the default ObjectSet is available for each entity. For example, I have table Employee, after gererated Entity Model, EF will create ObjectSet on Employee.
Then when using wcf ria service, the default query will be like:
public IQueryable GetEmployee()
{
return this.ObjectContext.Employees;
}
With objectSet, I can apply include on the result like:
return this.ObjectContext.Employees.Include("Department");
Then I create a stored procedure say MySearchForEmployee and import it as function. the result is mapped to entity Employee. When call the function, the result will be ResultSet, not ObjectSet.
I want to similar method available for domain service by call the stored procedure like:
public IQueryable<Employeer> GetMySearch(string keyword)
{
return this.ObjectContext.MySearchForEmployee(keyword).Include("Department");
}
But I can't becuase above code event can't pass syntax checking.
I tried following way to convet the result type:
var results = this.ObjectContext.MySearchForEmployee(keyword);
var objsets = (ObjectSet<Employee>) results;
then I got error as:
Cannot convert type 'System.Data.Objects.ObjectResult' to 'System.Data.Objects.ObjectSet'
How to implement this request?
There is no reason to use an ObjectSet, because you cannot include multiple entity sets in one query from a stored procedure. This is not supported in the Entity Framework.
You could try the EFExtensions project, it has extensions to load multiple entity sets from one query.
Related
I'm wondering if there is any way to map a stored procedure result into into a class.
This is what I have:
// DbContext Class:
public DbSet<StoredProcedureModelResult> SPMR { get; set; }
// Service Class:
var result = ctx.Set<StoredProcedureModelResult>().FromSql("getXXXX p1 = {0},1).ToList();
This works well, however, I'm using database migrations and every time I add one this thing creates StoredProcedureModelResult as a table...
I tried to ignore it onModelCreating:
modelBuilder.Ignore<SPModels.test>();
but this throws an exception:
Cannot create a DbSet for 'StoredProcedureModelResult ' because this type is not included in the model for the context
I just want use the benefit of mapping, and not to get a table creation, this is a simple model (non-entityType)
BTW
.NET Core 1.1
Web API
EF Core (code-first)
Thank you
You don't need to make the type an Entity type (by registering a DbSet in your DbContext). Just have a method that returns IEnumerable<StoredProcResults> (can be in your DbContext), and in it run
dbContext.Database.SqlQuery<StoredProcResults>(...)
See Database.SqlQuery<T>(...)
When using LINQ to retrieve data we can also get its navigation properties with an include as follows:
IQueryable<Location> locations = from c in ClientContext.Locations.Include("LocationType") select c;
return locations;
How can we do the same, when we call a SP through the EF? I have a function import which returns the same object as the above query does:
return (IQueryable<Location>)ClientContext.GetLocationsPerUser(userId, getSubLocations);
How can I attach the LocationType entity to the above set? Is it possible or will I have to expose it from the SP itself?
I'm using EF5 Model First. I don't really understand what are the auto-generated classes from the EDM. According to some documentation this classes are POCOs but why are they used in the context ?
Assuming I have a Student entity, then I get a Student POCO class and a DbSet StudentSet property in my context.
Will this next instructions put a POCO in my database ?
MyContext.StudentSet.Add(johndoe);
MyContext.SaveChanges();
So EF uses POCO to transfer data ? Actually I miss the step when POCO exchange data with entities or DTO and when the entities put data in the database.
The generated classes from the EDM is the ORM / Persistence classes. You use that classes to query / make changes from / to database. You need to translate any DTO object to POCO object when about making changes to database.
ORM is about mapping object to data in database, instead of dealing with insert into syntax to insert record to database in the application, you use StudentSet.Add to add a new data. The johndoe information will be translated into sql syntax, EF will map each property to each column when translating it into query.
The Add method will store the johndoe information as Added in the memory but it will not be executed right away to the database. If you have another Add method, it will be marked as Added too. The moment you call SaveChanges, all the changes will be saved into database by sending a generated query.
The mapping between DTO and EF entity happens before you add the johndoe. You might have another DTO class that is used in the UI. You need to map it manually or using mapper library to create a POCO object from a DTO object. For example:
// studentDto as parameter
var johndoe = new Student
{
Name = studentDto.StudentName,
Age = studentDto.StudentAge
};
MyContext.StudentSet.Add(johndoe);
// studentDto might have another information as well
var johndoeSubject = new Subject
{
Name = studentDto.SubjectName,
Years = studentDto.SubjectYears
};
MyContext.SubjectSet.Add(johndoeSubject);
MyContext.SaveChanges();
We're using a Function Import in an EF4 model to populate an existing entity in our Model. The entity in the model has a Key field of Id which we're struggling to map as our stored procedure doesn't return an Id field. I've tried setting the value in the mapping to a literal value of 0 but that fails with an EntityCommandExecutionException and the following exception text.
The data reader is incompatible with the specified 'Candidate'. A member of the type, 'Id', does not have a corresponding column in the data reader with the same name.
Short of modifying the stored procedure to return a dummy Id field can anyone recommend what the best approach is for this as the dummy field option feels very clunky to me.
Many Thanks
If you can't return enough data to fully materialize the entity -- and the Id field is certainly going to be required for that -- then you need to change the return type on the proc to be a complex type instead of an entity.
Use another POCO class with the same structure to receive the results of the stored procedure call, here's an example:
string sp = string.Format("EXEC dbo.spComercialesAsociadosActivos {0}", idComercialPrincipal);
return ((IObjectContextAdapter)this).ObjectContext.ExecuteStoreQuery<InfoComercial>(sp);
In this case "InfoComercial" is a POCO class with the same structure as "Comercial", which is tied up to EF code first in the DBContext, then I used this independent class in the viewModel to create a disconnected "Comercial", it's not an ideal solution but will work fine until EF 5 comes with SP support.
I've created a function import that returns the results of a stored proceedure as one of my entities. however I can't seem to traverse my through navigation properties to access the data in other entities. I know that you can use include() for objectQueries but can't find anything that will force the EF to load my relations for entity results of function imports.
Any ideas??
Thanks in advance.
This is not possible in EF 1.0
The reason is that EF will consider stored procedure values to be just values and not navigation properites.
For example, Employee entity has multiple Order entities. In Order you have a property called EmployeeID. When the database fills your query using include statements, it creates 1 projection query in SQL to populate all of the Order data that a particular Employee could have.
So if I said
var employee = context.Employees.Include("Orders").Where(e => e.ID == 1).First();
var orders = employee.Orders;
The SQL for the first query will create a projection query which will contain orders where the EmployeeID = 1.
Now when your stored procedure runs, this can do any code behind the scenes (in otherwords it can return any set of data). So when SQL runs the stored procedure, it just runs the code in that stored procedure and does not have any knowledge that EmployeeID on Order is an FK to that property. Additionally, if your stored procedure returns an Employee entity, then you are looking at another scenario where you will not even have an OrderID to pursue.
To work around this though, you can setup your query in EF using Include statements that can mirror any stored procedure. If you use the proper mix of .Select and .Include statements you should be able to do the same thing.