How to get newly added entities in EF Core - entity-framework

Question

I am adding new entity by creating the instance using inline syntax.
public async Sys.Task<IEnumerable<Car>> CreateCars()
{
for (int i = 0; i < 2; i++)
{
await _dbContext.Cars.AddAsync(new Car()
{
// set properties here
});
}
await _dbContext.SaveChangesAsync();
// How do return list of newly added Cars here without querying database
}
How do i return newly added Car without querying the database?
One option i know is add new instance to list, and use AddRange method of dbContext like below
public async Sys.Task<IEnumerable<Car>> CreateCars()
{
var list = new List<Car>();
for (int i = 0; i < 2; i++)
{
list.Add(new Car()
{
});
}
await _dbContext.Cars.AddRangeAsync(list);
await _dbContext.SaveChangesAsync();
return list;
}
But i would like to avoid creating unnecessary instance of list.
I am using EF Core 2.2.4

Answer 1

Use the Local property of your Cars DbSet. I contains a local view of the tracked entities.

Answer 2

There doesn't seem to be a built-in function for that. You could make a generic extension method though.
public static class DbSetExtensions
{
public static async Task<T[]> AddRangeAsyncExt<T>(this DbSet<T> dbSet, params T[] entities) where T : class
{
await dbSet.AddRangeAsync(entities);
return entities;
}
public static async Task<IEnumerable<T>> AddRangeAsyncExt<T>(this DbSet<T> dbSet, IEnumerable<T> entities) where T : class
{
await dbSet.AddRangeAsync(entities);
return entities;
}
}
// use case 1
var cars = await _dbContext.Cars.AddRangeAsyncExt(new Car(), new Car(), new Car());
// use case 2
var cars = await _dbContext.Cars.AddRangeAsyncExt(
new[] { 1, 2, 3 }
.Select(i => new Car
{
// set properties here
}));