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C#, Entity Framework, How to Update(delete, add, edit) multiple rows at same time?

Sometimes, we would like to change order details by adding, removing, and editing orders by customer's request or depends on stock quantity.
So now want get some list and update including remove, edit, add rows, then save on database
What's the best efficiently way as C#, EntityFramework?
public class OrderDetail
{
public int Id { get; set; }
public int OrderId {get; set; }
public int Qty{ get; set; }
public string ItemName { get; set; }
}
/// Dummy db, OrderDetail Table
{
{1, 1000, 24,"A"},
{2, 1000, 12,"B"}
}
public void Update()
{
using(var db = new xxEntities())
{
// Get All orders, OrderId==1000, total 2rows
List<OrderDetails> list = db.OrderDetails.Where(x=> x.OrderId==1000).ToList();
// remove some row or rows
var temp1 = list.First(x=> x.Id==1);
list.Remove(temp);
// edit some row or rows
var temp2 = list.First(x=> x.Id==2);
temp2.Qty=100;
// add some row or rows
list.Add(new OrderDetail{ Id=3, OrderId=1000, Qty=2, ItemName="C"});
list.Add(new OrderDetail{ Id=4, OrderId=1000, Qty=2, ItemName="D"});
// Apply all changes
db.SaveChanges();
}
}
Additional Question
public void UpdateOrder(int orderId, List<OrderDetail> newOrders)
{
var result = db.OrderDetails.Where(x=>x.OrderId==orderId).ToList();
result = newOrders;
// it does not work
//db.OrderDetails.Update(result);
db.OrderDetails.RemoveRange(result);
db.OrderDetails.AddRange(newOrders);
db.SaveChange();
}
is it right approach to update multiple rows?

As mentioned in another answer... EF will create individual statements for each of the changes that are detected (i.e., updates, inserts, deletes) and submit them inside a single transaction. Gets the job done but is potentially very "chatty". Benefit is that you don't need to worry about the details of how it's getting done. Pretty easy to just modify the data object and call SaveChanges.
If you can consider not using EF for updates such as this... one way we do this kind of update is by creating a System.Data.DataTable and using that as a table-valued parameter into a stored procedure (if your datastore supports it).
Meta-code:
var dt = new DataTable();
var newRow = dt.NewRow();
newRow["column1"] = newdata;
dt.Rows.Add(newRow);
Then just use dt as your input parameter and let the stored proc determine the insert/update/delete operations.

If you want to Add / Remove / Update rows from your tables in Entity Framework, you have to Add / Remove / Update the items in your DbSet, not in fetched data.
using (var dbContext = new OrderContext())
{
// Add one Order
Order orderToAdd = new Order
{
// fill required properties; don't fill primary key
}
var addedOrder = dbContext.Orders.Add(orderToAdd);
// note: addedOrder has no Id yet.
// Add several Orders
IEnumerable<Order> orders = ...
dbContext.Orders.AddRange(orders);
dbContext.SaveChanges();
// now they've got their id:
Debug.Assert(addedOrder.Id != 0);
Debug.Assert(orders.All(order => order.Id != 0);
}
To Remove, you'll first have to fetch the complete Order
int orderIdToDelete = ...
using (var dbContext = new OrderContext())
{
Order orderToDelete = dbContext.Orders.Find(orderIdToDelete);
dbContext.Orders.Remove(orderToDelete);
var ordersToDelete = dbContext.Orders
.Where(order => order.Date.Year < 2000)
.ToList();
dbContext.Orders.RemoveRange(ordersToDelete);
// the orders are not deleted yet.
dbContext.SaveChanges();
}
To Update, you first have to get the value:
int orderIdToUpdate = ...
Order orderToUpdate = dbContext.Orders.Find(orderIdToUpdate);
orderToUpdate.Date = DateTime.Today;
var today = Datetime.Today;
var dateLimit = today.AddDays(-28);
var nonPaidOrders = dbContext.Orders
.Where(order => !order.Paid && order.Date < dateLimit)
.ToList();
foreach (var order in nonPaidOrders)
{
this.SendReminder(order);
order.ReminderDate = today;
}
dbContext.SaveChanges();

There is no "most efficient" way outside of making all changes then calling SaveChanges. upon which Ef will issue a lot of SQL Statements (one per operation).
There is most efficient way because there is no way to change the way Ef works and there is exactly one way Ef does its updates. They do NOT happen at the same time. Period. They happen in one transaction, one after the other, when you call SaveChanges.

Entity Framework only save single record from the list

I'm trying to insert a new record from TPOSTransaction and TPOSTransactionDetail
The code below is from an event in my class:
_posTransaction = new TPostransaction();
_posTransactionDetail = new TPostransactionDetail();
_posTransactionDetails = new List<TPostransactionDetail>();
_posTransaction.UserId = _user.Id;
_posTransaction.Total = Convert.ToDecimal(txtOrderTotal.Text);
_posTransaction.ChangeDue = Convert.ToDecimal(txtChangeDue.Text);
_posTransaction.AmountPaid = Convert.ToDecimal(txtAmountPaid.Text);
_posTransaction.TransactionDate = DateTime.Now;
foreach (ListViewItem orders in lvOrders.Items)
{
_posTransactionDetail.ItemId = Convert.ToInt32(orders.SubItems[1].Text);
_posTransactionDetail.Quantity = Convert.ToInt32(orders.SubItems[3].Text);
_posTransactionDetail.Subtotal = Convert.ToDecimal(orders.SubItems[4].Text) * Convert.ToDecimal(orders.SubItems[3].Text);
_posTransactionDetails.Add(_posTransactionDetail);
}
_posTransaction.TPostransactionDetail = _posTransactionDetails;
_pos.Add(_posTransaction); //method from a class
This is where I save the record:
When I try to debug, POSTransaction.TposTransactionDetail have 2 records since it's what I added from the list
//this is my primary concern
var posTransaction = dbContext.TPostransaction.Add(POSTransaction);
dbContext.TPostransactionDetail.AddRange(POSTransaction.TposTransactionDetail);
dbContext.SaveChanges();
This saves the record of TPosTransaction and TPosTransactionDetail, but the detail that is being saved is only one, instead of 2. I tried removing the AddRange part it still saves a single record in my TposTransactionDetail.

on you foreach you need to create new instance of TPostransactionDetail, you are just reusing the instance on the top of your code.

The property 'ID" is part of the object's key on INSERT

We have to transfer data from one database to another. So I tried to write a program, which reads tables from the old database, create Entities and store them afterwards in the new database. At the beginning it worked very good. I tried to read only one table and transfer it to the new one. Now i receive the following error:
"The property 'Id' is part of the object's key information and cannot
be modified.
No I dont get rid of that error. Even if I try to get back to the first implementation (which worked like a charm).Here I have the definition of the Table:
Table definition
And here the code:
class MappingUtility
{
public static IEnumerable<Nation> MapNation(DataTable table, IModelFactoryService service)
{
IEnumerable<DataRow> rows = table.AsEnumerable();
Nation nat = service.Create<Nation>();
foreach(var nation in rows)
{
nat.Id = (System.Guid)nation.ItemArray[0];
nat.HVCode = (string)nation.ItemArray[1];
nat.Kurzbezeichung = (string)nation.ItemArray[2];
nat.KFZ = (string)nation.ItemArray[3];
nat.iso_a2 = (string)nation.ItemArray[4];
nat.iso_a3 = (string)nation.ItemArray[5];
nat.iso_n3 = (string)nation.ItemArray[6];
nat.Vollbezeichung = (string)nation.ItemArray[7];
nat.Updated = DateTime.Now;
nat.Created = DateTime.Now;
yield return nat;
}
}
}
using (var da = new SqlDataAdapter("SELECT * FROM NATION", "....."))
{
var table = new DataTable();
da.Fill(table);
using (var context = new DAtenbankContext())
{
int i = 0;
foreach (var nation in MappingUtility.MapNation(table, ef6))
{
Debug.WriteLine(i++);
if (context.Nation.Where(p => p.Id == nation.Id).FirstOrDefault() == null)
{
try
{
context.Entry(nation).State = EntityState.Added;
context.SaveChanges();
}
catch(DbEntityValidationException ex)
{
Debug.WriteLine("");
}
catch (DbUpdateException ex)
{
Debug.WriteLine("There where some duplicate columns in the old table.");
Debug.WriteLine(ex.StackTrace);
}
}
}
}
}
Note: The id is not autogenerated. If I try to create only one Nation at a time i can insert it. Even with this for loop I insert one nation, at the second iteration I get the error.

I suspect that you're operating on the same instance of Nation with every iteration of the loop. It appears that you only ever create one instance and then modify it over time. Entity Framework is trying to track that instance, so modifying the key is confusing it.
Move the instantiation into the loop so that you're creating new instances:
IEnumerable<DataRow> rows = table.AsEnumerable();
foreach(var nation in rows)
{
Nation nat = service.Create<Nation>();
// ...
yield return nat;
}

How can I edit or add to a particular field without pull the all object

How I can do just this ( a.myFavorits.Add()) without pulling the all object to var a , because a has a lot of data, and I don't want to pull all a object, but I can't find a way do do it.
I want to do the lambada and the linq without return something but linq is always return something
public static void addFavorits(long f,long idUser)
{
using (var db = dataBase())
{
// here i pull object user from users table
var a = db.users.Where(c => c.id == idUser).SingleOrDefault();
// here i adding to the object field myFavorits new value
//myFavorits is also a table of entitys that connected to user object
a.myFavorits.Add(new BE.FavoritsUsersLong { myLong = f });
db.SaveChanges();
}
}
I thought to do something like this but i dont know how to set the field users_TableId that is the key that connect the 2 tables
public static void addFavorits(long favoritId,long idUser)
{
using (var db = dataBase())
{
db.favoritsUsersLong.Add(new BE.FavoritsUsersLong {myLong = favoritId}
/*,users_TableId =idUser*/);
db.SaveChanges();
}
}

Here's a concrete example that does what you want. In this example, only the Name of a Company is modified and saved. Or an item is added to one of its collections.
var cmp = new Company{ CmpId = 1, Name = "Cmp1" }; // CmpId is the primary key
db.Companies.Attach(cmp);
db.Entry(cmp).Property(c => c.Name).IsModified = true;
// Or add an entity to a collection:
cmp.Users = new[] {new User { Name = "a1", PassWord = "a1" } };
try
{
db.Configuration.ValidateOnSaveEnabled = false;
db.SaveChanges();
}
finally
{
db.Configuration.ValidateOnSaveEnabled = true;
}
Result in SQL:
DECLARE #0 VarChar(30) = 'Cmp1'
DECLARE #1 Int = 1
UPDATE [dbo].[Company]
SET [Name] = #0
WHERE ([CmpId] = #1)
There are a few things to note here:
Obviously you need to know the Id of the entity you want to modify.
The object you create is called a stub entity, which is an incomplete entity. When you try to save such an entity, EF is very likely to complain about null values in required properties. That's why almost certain you'd have to disable validation (temporarily, or, better, dispose the context immediately).
If you want to add an item to a collection, you should leave validation enabled, because you'd want to know for sure that the new entity is valid. So you shouldn't mix these two ways to use a stub entity.
If you often need roughly the same small part of your entity you may consider table splitting.

I'm guessing this is what you want? I don't see you 'editting' I only see you adding.
using (var db = dataBase())
{
var a = new user();
....
//set properties etc..
...
a.myFavorits.Add(new BE.FavoritsUsersLong { myLong = f });
db.users.Add(a);
db.SaveChanges();
}

MVC AddObject Create multiple records

I have a list which contains multiple records. I like to use the AddObject to create those records but what is happening is that it creates just the last record in the list.
Here is the code
foreach (var item in invlist) {
invmodel.tblrec.FirstName = item.FirstName;
invmodel.tblrec.LastName = item.LastName;
db.tblRec.AddObject(invmodel.tblrec);
}
db.SaveChanges();

I would start with this very simple modification of your code:
foreach (var item in invlist) {
var tblRec = new TblRec();
tblRec.FirstName = item.FirstName;
tblRec.LastName = item.LastName;
db.tblRec.AddObject(tblRec);
}
db.SaveChanges();
Why? Because your code is repeatedly adding the same instance and for EF it is still the same object - it will either result in exception or only the last item will be inserted to database.