C＃实体框架插入而不是更新

Question

Let say I have a 11,000 customers in the list 'customersFromFile' and 8000 customers in DB

With the code below, I expect EF will update the existing 8000 customers in DB, and add 3000 left to DB

The console are printed correctly with "Updated customers: 8000" and "Added to customers: 3000

However in DB now I have total 19000 customers although the existing 8000 are updated successfully.

Please help me on this.

DEMOEntities context = new DEMOEntities();
context.Configuration.AutoDetectChangesEnabled = false;
context.Configuration.ValidateOnSaveEnabled = false;

int i = 0;
foreach (var customerInDB in context.Customers)
{
    //Console.WriteLine("Update customer: " + customerInDB.CustomerID.ToString());
    customerInDB.Name = customersFromFile[i].Name;
    customerInDB.CIC = customersFromFile[i].CIC;
    customerInDB.IndustryCode = customersFromFile[i].IndustryCode;
    context.Entry(customerInDB).State = EntityState.Modified;
    i++;
}

Console.WriteLine("Updated customers: " + i.ToString());

int j = 0;
for (; i < customersFromFile.Count; i++)
{
    context.Customers.Add(customersFromFile[i]);
    j++;
}
Console.WriteLine("Added to customer:" + j.ToString());    

Console.WriteLine("Saving changes to customer...");
context.SaveChanges();

Update 2: Thanks TomTom for this answer, my mistake to add customer to context when I form up the CustomerFromFile List. It took me hours to discover this :(

Answer 1

This sounds like you have no unique identifier for your customers.

In the second loop, you should check if the 'customer from file' isn't already in DB before adding it (probably basically same Name, same CIC and same IndustryCode).