I'm fairly new to entity framework and patterns. How would I insert data into a child table?
I inserted the information into the parent table. Do I have to return the identity of the row and then issue another insert?
User Table and User Role.
I've been trying to find a solution for a day now, but I think its because I'm searching the wrong results. My structure is set up using Unit of Work/Repository Pattern.
Any help would be helpful. Thanks!
Get the Parent object. Add the child record to it's navigation property.
something like this
int orderId=33;
var parent=dbContext.Orders.Where(x=>x.Id==orderId);
parent.Details.Add(new OrderDetail{ Quantity=4, ItemId=37});
parent.Details.Add(new OrderDetail{ Quantity=2, ItemId=48});
dbContext.SaveChanges();
Assuming Order is your Master entity and Detail is your child entity and dbContext is your DBContext class object.
EDIT : If you are adding it together,
Order parent=new Order { CustomerId=35, Discount=43.63 };
parent.Details.Add(new OrderDetail{ Quantity=4, ItemId=37});
parent.Details.Add(new OrderDetail{ Quantity=2, ItemId=48});
dbContext.Orders.Add(parent);
dbContext.SaveChanges();
Related
Maybe simple, but I can't figure it out...
When I create a record using Eloquent and a model that extends Model, and then get its id right after it just works:
$example = Example::create(['name'=> 'exie']);
dd($example->id);
// returns id (ex. 15) as expected from the created record...
When I create a record using a model that extends Pivot and try to get id, it only returns null.
$customPivotExample = CustomPivot::create(['name' => 'custie']);
dd($customPivotExample->id);
// returns null instead of id...
The records all have a PK so I expected to just get the ID back, but apparently there is something about using a custom pivot model and getting it's id after creation what I am overlooking..
(examples are really simple but the actual code only contains more key=>value pairs and nothing more)
anyone has any idea?
Own Answer
Putting this here because this is not written (somewhat) in the Laravel documentation.
They mention this about auto incrementing ID's:
https://laravel.com/docs/9.x/eloquent-relationships#custom-pivot-models-and-incrementing-ids
I had not done this (my bad), but doing this also enables getting the ID after creation of a pivot record as in my second example....
There is a table, it is a poco entity generated by entity framework.
class Log
{
int DoneByEmpId;
string DoneByEmpName
}
I am retrieving a list from the data base. I want distinct values based on donebyempid and order by those values empname.
I have tried lot of ways to do it but it is not working
var lstLogUsers = (context.Logs.GroupBy(logList => logList.DoneByEmpId).Select(item => item.First())).ToList(); // it gives error
this one get all the user.
var lstLogUsers = context.Logs.ToList().OrderBy(logList => logList.DoneByEmpName).Distinct();
Can any one suggest how to achieve this.
Can I just point out that you probably have a problem with your data model here? I would imagine you should just have DoneByEmpId here, and a separate table Employee which has EmpId and Name.
I think this is why you are needing to use Distinct/GroupBy (which doesn't really work for this scenario, as you are finding).
I'm not near a compiler, so i can't test it, but...
Use the other version of Distinct(), the one that takes an IEqualityComparer<TSource> argument, and then use OrderBy().
See here for example.
I have a "task" table, which has a "sub category". The sub category is related to a Category. A category has many sub categories, but my task item only stored the sub category id (The category can be deduced from this).
So, my entity framework seems to understand this relationship.
But, my link is failing.
public TaskObject GetTask(int taskId)
{
var item = (from t in _te.tasks.Include("r_sub_category").Include("r_category").Include("r_priority").Include("r_state").Include("assigned_person").Include("create_person").Include("update_person") where t.task_id == taskId select t).FirstOrDefault();
return Transformer.UnpackTask(item);
}
There is a r_category table, and entity object, but when I run this, it tells me:
A specified Include path is not valid. The EntityType 'taskerModel.task' does not declare a navigation property with the name 'r_category'.
And that's correct - r_category is linked to my r_sub_category table... and not directly to task. Is there a way to load the r_category?
Or, maybe this Include is lazy, and I should be doing some sort of Joining myself? Maybe more efficient?
You need to show the full path with dot Notation so im guessing it would be
"r_sub_category.r_category".
And so forth
how can I build a table of "orders" containing "IdOrder", "Description" and "User"?... the "User" field is a reference to the table "Users", which has "IdUser" and "Name". I'm using repositories.
I have this repository:
Repository<Orders> ordersRepo = new OrderRepo<Orders>(unitOfWork.Session);
to return all Orders to View, I just do:
return View(ordersRepo.All());
But this will result in something like:
IdOrder:1 -- Description: SomeTest -- User: UserProxy123ih12i3123ih12i3uh123
-
When the expected result was:
IdOrder:1 -- Description: SomeTest -- User: Thiago.
PS: I don't know why it returns this "UserProxy123ih12i3123ih12i3uh123". In Db there is a valid value.
The View:
It is showed in a foreach (var item in Model).
#item.Description
#item.User //--> If it is #item.User.Name doesn't work.
What I have to do to put the Name on this list? May I have to do a query using LINQ - NHibernate?
Tks.
What type of ORM are you using? You mention "repositories" but does that mean LinqToSql, Entity Framework, NHibernate, or other?
It looks like you are getting an error because the User field is not loaded as part of the original query. This is likely done to reduce the size of the result set by excluding the related fields from the original query for Orders.
There are a couple of options to work around this:
Set up the repository (or context, depending on the ORM) to include the User property in the result set.
Explicitly load the User property before you access it. Note that this would be an additional round-trip to the database and should not be done in a loop.
In cases where you know that you need the User information it would make sense to ensure that this data in returned from the original query. If you are using LinqToSql take a look at the DataLoadOptions type. You can use this type to specify which relationships you want to retrieve with the query:
var options = new DataLoadOptions();
options.LoadWith<Orders>(o => o.User);
DataContext context = ...;
context.LoadOptions = options;
var query = from o in context.Orders
select o;
There should be similar methods to achive the same thing whatever ORM you are using.
In NHibernate you can do the following:
using (ISession session = SessionFactory.OpenSession())
{
var orders = session.Get<Order>(someId);
NHibernateUtil.Initialize(orders.User);
}
This will result in only two database trips (regardless of the number of orders returned). More information on this can be found here.
In asp.net MVC the foreign key doesn't work the way you are using it. I believe you have to set the user to a variable like this:
User user = #item.User;
Or you have to load the reference sometimes. I don't know why this is but in my experience if I put this line before doing something with a foreign key it works
#item.UserReference.load();
Maybe when you access item.User.Name the session is already closed so NHib cannot load appropriate user from the DB.
You can create some model and initialize it with proper values at the controller. Also you can disable lazy loading for Orders.User in your mapping.
But maybe it is an other problem. What do you have when accessing "#item.User.Name" from your View?
I would like to populate a Treeview.
Here is what I have in DB :
table : Box
BoxID
BoxName
table Book :
BookID
BookName
BoxID (fk Box.BoxID)
table Chapter:
ChapterID
ChapterName
BookID (fk Book.BookID)
As you may know a treeview is made up of treenode object.
A treenode object have a text property and a tag property.
The "text" property is the text that it's display on the screen for this node and the "tag" is an "hidden" value (usually uses to identify a node)
So in my case; the fields ending with ID will be used in the "tag" property and the fields ending with Name will be used in the "text" property
example :
so for a book; I will use the BookID field for the "tag" property and BookName field for the "text" property
note : I use a dbml so I have a Book object, Box object and Chapter object and I use linq to get them from the db.
So my question is; what is the best practice to build this tree?
I have a solution but it's really ugly because it looks like I'm duplicating the code.
The problem is that the values I need to extract for the text and tag properties are identified by differents fields name in the db
So for the book level, I need to get the BookID field to populate the tag property of my node; for the box level, I need to get the BoxID field to populate the tag property , ....
How can I make a kind of generic way to do it ?
I hope I made myself clear enough, don't hesitate to ask me questions :)
Thx in advance
Here is what I have for the moment
I get the list of box with a linq (dbml) request.
List<Box> MyListofBox = getMyListofBox();
Treenode tnBox = null;
Treenode tnBook =null;
foreach(Box b in MyListofBox )
{
tnBox = new TreeNode();
tnBox.tag = b.BoxID;
tnBox.text = b.BoxName;
List<Book> MyListofBook = getMyListofBookByBoxID(b.BoxID)
foreach(Book boo in MyListofBook )
{
tnBook = new TreeNode();
tnBook.tag = boo.BookID;
tnBook.text = boo.BookName;
tnBox.nodes.add(tnBook);
}
mytreeview.nodes.add(tnBox);
}
but of course I don't like this solution...
do you have a better way ?
I would extract the you need from the database in the form of a struct, possibly via the anonnoumous type that has been added to C# together with linq. Then I would populate insert this data into the place in the tree.
From what I get, you are trying to get each property separately, which will not work so well, because then you will have to make a call to the database for each separate property, which is very wasteful.
Addition based on what you have added
I do not believe the code can be more compact - the names you call are similar, but not the same and the way you do it was what I was trying to explain earlier.
You could
Define an key/value interface that both Box and Book implement
Define a delegate that returns a TreeNode and create delegate methods that accept Box and Book
However, I think the code is fine as written. Sometimes you just have to code it and there's little point in further abstracting or optimizing it.
The only issue I see in the code is that you're making a database call in a loop. Whether or not that's a problem depends on the application.