are we able to Include(x=>x.Entity) then Select(x=> new Entity{ A=x.A }) - linq

Question

I'm trying to call my CompanyCatalog table with its FileRepo table. There is a One to One relationship between them and i wanna apply when i Include(x=>x.FileRepo.Select(a=> new{ FileName=a.FileNAme} )) or any query like that.
Let me show to you my query in the bellow :
return TradeTurkDBContext.CompanyCatalog.Include(x=>x.FileRepo
.Select(x=> new FileRepo(FileName=x.FileName))).AsNoTracking().ToList();
I'm trying to do something like that. I'm asking is it possible or not ? if it's possible then how ?

Answer 1

So you have a table of CompanyCatalogs and a table of FileRepos. Every CompanyCatalog has exactly one FileRepo (one-to-one), namely the one that the foreign key refers to.
If you've followed the entity framework conventions, you will have classes similar to the following:
class CompanyCatalog
{
public int Id {get; set;}
public string Name {get; set;}
... // other properties
// every CompanyCatalog has one FileRepo, the one that the foreign key refers to
public int FileRepoId {get; set;}
public virtual FileRepo FileRepo {get; set;}
}
class FileRepo
{
public int Id {get; set;}
public string Name {get; set;}
... // other properties
// every FileRepo is the FileRepo of exactly one CompanyCatalog
// namely the one that the foreign key refers to
public int CompanyCatalogId {get; set;}
public virtual CompanyCatalog CompanyCatalog {get; set;}
}
This is enough for entity framework to detect your tables, the columns in the tables and the relations between the tables. If you had a one-to-many, you would have had a virtual ICollectioni<...> on the "one side". Only if you deviate from the conventions, for instance because you want other table names, or other column names, you need attributes or fluent API.
In entity framework the columns are represented by non-virtual properties. The virtual properties represent the relations between the tables (one-to-many, many-to-many, etc)
Foreign keys are columns in a table, hence they are not virtual. FileRepo is no column in the CompanyCatalogs table, hence it is declared virtual.
You want several properties of CompanyCatalogs, each with several properties of their FileRepos. You use Include for this. This is not necessary. A simple Select will do.
var companyCatalogs = dbContext.CompanyCatalogs
.Where(catalog => ...) // only if you don't want all CompanyCatalogs
.Select(companyCatalog => new
{
// Select only the CompanyCatalog properties that you plan to use:
Id = companyCatalog.Id,
Name = companyCatalog.Name,
...
// Select the FileRepo of this CompanyCatalog as one sub object
FileRepo = new
{
Date = companyCatalog.FileRepo.Date,
Title = companyCatalog.FileRepo.Title,
...
},
// if you want you can select the FileRepo properties one by one:
FileRepoDate = companyCatalog.FileRepo.Date,
FileRepoTitle = companyCatalog.FileRepo.Title,
});
Entity Framework knows your relations, and because you used the virtual properties of the class, it knows it has to perform a (Group-)Join.