How to update tables many times with Entity Framework - entity-framework

Question

I have two tables with relationships, they are :
Table users - Table Region
----------------- -----------------
' idUser ' ' idRegion '
'-------------- ' '---------------'
' email ' ' regionName '
'---------------' '---------------'
' password '
'---------------'
' user_name '
'---------------'
' phone_number '
'---------------'
' id_Region '
'---------------'
In my case, it has three states of inserting and updating datas.
The user will populate just the Email and password rows.
The user is able to populate the rest of rows including the RegionName.
And finally, the user can update any rows that he wants but email and password.
So, the first case I already did, it's easy, the second works fine, but the problem is when I try to update for the second time, inside of my Regiontable it creates a new row instead of change the selected field.
My Code :
public HttpResponseMessage Update(UsersGetModel usersGetModel)
{
using (var context = new GoneDatabase())
{
try
{
var user = context.users.Where(a => a.idUser== usersGetModel.id).FirstOrDefault();
user.userName = usersGetModel.Name;
user.PhoneNumber = usersGetModel.PhoneNumber;
user.Region = new region{ regionName= usersGetModel.Region };
context.Entry(user).State = System.Data.Entity.EntityState.Modified;
context.SaveChanges();
return Request.CreateResponse(HttpStatusCode.OK);
}
catch (Exception ex)
{
return Request.CreateResponse(HttpStatusCode.BadRequest);
}
}

Answer 1

It's creating a new row because you're literally telling it to by constructing a new Region instance at
user.Region = new region{ regionName= usersGetModel.Region };
Rather, you need to retrieve an existing Region instance from the DbContext and use that, like
user.Region = context.Set<Region>().Where(r => r.Name.Equals(usersGetModel.Region).SingleOrDefault();
A couple notes:
"SingleOrDefault" will throw an exception if there is more than one row in the Region table that matches the "Where" criteria
You need to put some constraints on your database tables to prevent #1 from happening, if business logic/specs indicate it