How do I use projection to insert data in EF Core-CodePudding

I am trying to write to the database using projection to avoid having to map a domain object to one that matches the table layout. Every projection example that I find however only shows how to read from the database. How do I project my entity to its database version to insert it?

class Foo
{
   //...
}

class FooEF
{
   //...
}

DbSet<FooEF> dbSet;

// Read
var foos = dbSet.Select(fooEF => new Foo { ... }).ToList();

// Write
???

CodePudding user response：

You cannot do that with EF Core. Any Insert/Update/Delete should go via change tracker.

Anyway there is extension linq2db.EntityFrameworkCore which can help in such query (disclaimer: I'm one of the creators)

var foos = dbSet.Select(fooEF => new Foo { ... });

foos.Insert(dbSetFoo.ToLinqToDBTable(), x => x);

Extension will create INSERT FROM SQL and no data will be transferred to the client.

CodePudding user response：

You need to use your db context. And you have to define dbSet for Foo type


public class ApplicationDbContext : DbContext
{
    public DbSet<Foo> DbSetFoo{ get; set; }
    public DbSet<FooEF> DbSetFooEF { get; set; }
    ...
}

...

var foos = dbSet.Select(fooEF => new Foo {...}).ToList().ForEach(foo=>context.DbSetFoo.Add(fooEf));
context.SaveChanges();