不选择MySQL的情况下更新对象

Question

Is it possible to update objects with Entity Framework, without grabbing them first?

Example: Here, I have a function that provides a Primary Key to locate the objects, pulls them, then updates them. I would like to eliminate having to pull the objects first, and simply run an UPDATE query. Removing the need for the SELECT query being generated.

    public async Task<int> UpdateChecks(long? acctId, string payorname, string checkaccountnumber, string checkroutingnumber, string checkaccounttype)
    {
        using (var max = new Max(_max.ConnectionString))
        {
            var payments = await
                max.payments.Where(
                    w =>
                        w.maindatabaseid == acctId && (w.paymentstatus == "PENDING" || w.paymentstatus == "HOLD")).ToListAsync();

            payments.AsParallel().ForAll(payment =>
            {
                payment.payorname = payorname;
                payment.checkaccountnumber = checkaccountnumber;
                payment.checkroutingnumber = checkroutingnumber;
                payment.checkaccounttype = checkaccounttype;
                payment.paymentmethod = "CHECK";
                payment.paymentstatus = "HOLD";
            });

            await max.SaveChangesAsync();
            return payments.Count;
        }
    }

Answer 1

You can use the Attach() command to attach an entity you already know exists and then call SaveChanges() will will call the appropriate update method. Here is some sample code from the MSDN article on the topic:

on the subject:

var existingBlog = new Blog { BlogId = 1, Name = "ADO.NET Blog" }; 

using (var context = new BloggingContext()) 
{ 
    context.Entry(existingBlog).State = EntityState.Unchanged; 

    // Do some more work...  

    context.SaveChanges(); 
}

Note that this is general EF logic, not related to any specific database implementation.