System.Data.DataException error occurred in EntityFramework.dll in asp mvc

Question

So I'm in trouble with this error:

An unhandled exception of type 'System.Data.Entity.ModelConfiguration.ModelValidationException' occurred in EntityFramework.dll.

Here is the code:

public ActionResult SaveItems(string[] fooItems, int category_id)
{
     foreach (item item in DB.items)
     {
          if (item.category_id == category_id)
          {
              if(item != null)
                  DB.items.Remove(item);

              DB.SaveChanges();
          }
     }
}

I'm trying to remove an item from the database, and save changes after that, when I get this error.

Any help is appreciated.

Thanks!

you can't mess with the underlying list while using a foreach as the yield will get thrown off — Alex Krupka
– Alex Krupka, Commented Nov 6, 2015 at 18:57

ataravati · Accepted Answer · 2015-11-06 19:44:07Z

3

As someone correctly mentioned in the comments, you cannot make changes to the underlying list while using a foreach loop. Change your action method to this:

public ActionResult SaveItems(string[] fooItems, int category_id)
{
     var itemsToRemove = DB.items.Where(i => i.category_id == category_id).ToList();

     DB.items.RemoveRange(itemsToRemove);
     DB.SaveChanges();
}

answered Nov 6, 2015 at 19:44

ataravati

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Comments

Vlad274 · Accepted Answer · 2015-11-06 19:44:44Z

0

You've got a couple issues:

You're modifying a list from within the foreach (as noted by Alex Krupka in a comment)
You're calling SaveChanges after every removal
This code loads each item one at a time, resulting in a lot of unnecessary calls to the DB
You're removing items from a method called "SaveItems"

I would use the following:

public ActionResult SaveItems(string[] fooItems, int category_id)
{
    var itemsToRemove = DB.items.Where(e => e.category_id == category_id)
                                .ToList();
    foreach (var item in itemsToRemove)
    {
        DB.items.Remove(item);
    }
    DB.SaveChanges();
}

answered Nov 6, 2015 at 19:44

Vlad274

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