How I can avoid optimistic concurrency exception when I delete rows?

user_1068094 0
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I have a method that receive the IDs of some rows to delete. I am using a code like this:

public bool delete(IEnumerable<long> paramIeId)
{
    using(myContext)
    {
        foreach(long iterator in paramIeId)
        {
            nyDbContext.Remove(new MyType(){ID = iterator});
        }
    }
}

It works fine because delete the rows when exists. But If there area 1 or more rows that doesn't exist then I get an exception and no one rows are delete, although some of them exists.

If I do this query in T-SQL I don't have problems, the database delete the exisiting rows and igonre the no exisiting rows because at the end I want to delete them so if another process deleted them for me, no problem.

I could handle the optimistic concurrency exception refreshing the dbContextfrom database, but I think that it is to do extra queries that they could be avoid.

Is there any way that EF works like T-SQL? If I try to delete a row that doen't exists, ignore it and delete the rest of the rows.

Thanks.

ef-core-2.0 optimistic-concurrency c#
2 Answers

You don't need to create a new object to delete it, just let EF handle everything for you:

public bool delete(IEnumerable<long> paramIeId)
{
    using(var nyDbContext = new DbContext())
    {
        foreach(long id in paramIeId)
        {
            MyType myType = nyDbContext.MyTypes.FirstOrDefault(x => x.ID == id);
            if (myType != null)
            {
                nyDbContext.MyTypes.Remove(myType);
            }
        }
        nyDbContext.SaveChanges();
     }
}
user_26730290

At least for now, the exception seems unavoidable when using detached entities to perform the delete. You'll either have to use a try / catch and handle the exception or query the DB for matching id's and only delete matches1.

Sample With Exception Handling

using (myContext)
{
    foreach (long iterator in paramIeId)
    {
        nyDbContext.Remove(new MyType() { ID = iterator });
    }

    try
    {
        nyDbContext.SaveChanges()
    }
    catch(DbUpdateConcurrencyException ex)
    {
        //if you want special handling for double delete
    }
}

Sample With Query then Delete

Note that I query the entire list of types before the loop to avoid making separate queries on each type.

using (myContext)
{
    var existingMyTypes = nyDbContext.MyTypes.Where(x => paramIeId.Contains(x.ID));
    foreach (MyType existing in existingMyTypes)
    {
        nyDbContext.Remove(existing);
    }

    nyDbContext.SaveChanges();
}

1 NOTE: The query then delete option leaves open a possible race condition which could trigger the OptimisticConcurrencyException you're trying to - namely, if another process / thread / program deletes the rows between your own processes's read and delete. The only way to completely handle that possibility is by handling the exception in a try / catch.

user_7942340
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