How to Update/Edit multiple records using Entity Framework in ASP.NET MVC
asp.net-mvc c# entity-framework
Question
I need to update multiple records, this is how far I could get
First, I tried this
foreach (var Product in Products)
{
Product.Price = Price;
db.Entry(Product).State = EntityState.Modified;
db.SaveChanges();
}
But, I'm getting this error
Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. Refresh ObjectStateManager entries.
Then, I found this answer, saying that I should create new instance for each iteration, but I got the same error. Below is my attempt.
foreach (var Product in Products)
{
var ProductInLoop = new Product();
ProductInLoop.Price = Product.Price;
db.Entry(ProductInLoop).State = EntityState.Modified;
db.SaveChanges();
}
Also I can't do it like this db.Entry(Products).State = EntityState.Modified; outside the loop, because Entry() expects a singel object.
How can I solve this?
Accepted Answer
Thanks to Ben Robinson's comment, I solved this. The problem caused because I didn't pass the primary key from View to Controller.
In View I added this hidden field to pass the primary keys like this:
<input type="hidden" name="[@i].id" value="@Product.id" />
and server side code look like this
foreach (var product in Products)
{
product.Price = Price;
db.Entry(product).State = EntityState.Modified;
}
db.SaveChanges();
Popular Answer
There is no need to create a new Product object. Since you are modifying records, your Products collection is likely already attached to the database context, and it's state will be tracked if you modify it.
Try this:
foreach (var Product in Products)
{
Product.price = ProductSize.price;
db.SaveChanges();
}
if the Products are not attached to the context (db), add this line before saving:
db.Products.Attach(Product);
by convention, you should also change your looping variable from Prodcut to the lowercase form : product
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