MVC :: What Is The Best Approach To One To Many Relationships
Aug 5, 2010
What is the best approach to one to many relationships?
This is my scenario:
I have a simple one to many relation:
Customer
CustomerID
Name
tel
CustomerNotes
Id
Note
customerID
I want to have a DETAIL view of customers and CREATE view for CustomerNotes all in the same page.
I create CustomerController and the different views and its respective actions for edit, create, delete, etc.
I also create a CustomerNotesController and the views and actions like before, but I made the views PARTIALS
I put a RENDERPARTIAL for the CustomerNotes create view in the Details view from Customer.
When I run the app, the page is render as expected: It shows the detail info of the customer and bellow the create form for the notes. However, when I click SAVE, nothing happens. I put a breakpoint in the notes controller and never get hit.
I also try with RenderAction and don't work at all.
I'm having a hard time wrapping my head around how to use the Memberships in MVC. I know there is the built in ASPNETDB database which has all the basic tables for users and such. But what if I wanted to add a relationship between one of my custom tables and this built in user table?
If I had a database table that contained blog comments, we'll call it Comment. And each Comment had a userID associated with it could I do something like?
Does anyone no of any good resources regarding many-to-many relationships? More specifically on displaying data from many-to-many tables in ASP. Struggling to find anything but I may just be over complicating things!
how to create C# classes to represent one to many relationships in C#. I have a Customer and an Address table in my database. I also have a Customer class in my C# solution but how do I introduce the multiple address element? Do I have a separate Address class? Do I create a subclass in the Customer class or create a method in Customer called GetAddresses of type List which contains all of the relevant logic? In my code I need to be able to return a customer with all associated addresses and I just cannot picture the best way to achieve this using OOP.
EF is so frustrating. I can't seem to be able to get my head around what I need to do so I can delete an object. I seem to be able to remove the object but not the related child objects. Can anyone tell me what is the rule of thumb when you want to delete all related child objects of a given object? I've tried loading all related objects like this:
Entry entry = ModelContext.GetObjectByKey(new EntityKey("ModelContainer.EntrySet", "Id", id)) as Entry; entry.ChildEnteries.Load(); if (entry != null) { ModelContext.DeleteObject(entry); ModelContext.SaveChanges(); }
I get errors related to the relationships: A relationship is being added or deleted from an AssociationSet 'EntryEntry'. With cardinality constraints, a corresponding 'Entry1' must also be added or deleted. Why can't I just load the object using modelcontext.GetObjectByKey and remove it along with its child objects? My other question is can I delete an object using Entity command like so? DELETE e from objectset as e where e.id = 1 I've tried few variations and all of them throw exceptions.
So I am working on an MVC project to put to work the studying I have been doing. I am wrestling with the concept of Database Table relationships and foreign keys. I am working on a simple ecommerce site (displays products, shopping cart, user accounts..etc).
I have the following tables to start out with:
1) Products
2) Categories
I setup the Products and Categories tables to have a ProductId and CategoryId respectively. In my MySQL db, I created a FK on the Products Table to relate to the CategoryId field on the Categories table (I am not sure this was correct to begin).
My expectations for the way the database would handle the table relationship: I didn't want the DB to do anything with the products table if I deleted a category out of the Categories table, or vise versa. The only thing would be that the category field in a Product would be blank (or default) if their category was removed.
Finally, do I have to do anything in my entity classes such as in the Products class, add the ProductId to the Category.ProductId?
Eventually, when I Orders and Users to the project, I can see a relationship where each user -> many orders -> each order has many products -> and each product is in one category.
But I am having a hard time understanding how or if I should be setting up a Foreign key relationship in the two current tables of Products and Categories and if so how to setup my entity class in relation to that FK.
this is a bit of a nomenclature question:what is the correct way to describe the relationships between these classes (the thing that throws me off is the use of generic types here):
Using dataloadoptions i have tried the following example
[Code]....
Now i need to ask how can i display Category ID and Category Name of the productID (i am supposing that One product can be in at most one category) by extending the above example Regards.
Say I have this entity with a lot of attributes. In the input form I have decided to implement a wizard control so I can collect information about this entity in several steps. The problem is that I need to collect information that has been modeled has many to many relationships. I am planning to use a telerik gridview to manage this (add/edit/delete), the problem is where do I store that data since the entity in a insert form is not created on the database yet. OK so I can store all that info in temporary lists residing in the viewstate, waiting for the final submit where I dump all that in the DB, but one of the steps I am collecting files...now storing files in the viewstate is out of the question, same as as storing them in the session...I have been thinking of implementing in a way that the user has to submit some info first (say first 3 steps), commit the data to the database creating the parent entity and then start inserting all the childs entities...but this will get weird as it's confusing since on the first steps you not saving the data to the DB and on the next ones you are commiting directly...
Just a quick question for those more familiar with FluentNHibernate. I've read the quick start things, and the docs on their site, but am still a tad off. Are the following maps correct, in terms of the HasOne / HasMany relationships? If not, correct them, and give me reasons, so I better understand.
C sharp Code:
[code]....
These will eventually go into a convention file, but for now, I just need to know how to code relationships period.
Users Id Username Email Password UserStatuses Id Name Users_UserStatus Id User (FK - Users: Id) Status (FK - UserStatuses: Id) StatusDate
As you can see, UserStatuses is a reference table with various statuses. Users_UserStatus is a join table between Users and UserStatuses. Using Entity Framework, how can I do a conditional to check if the latest StatusDate is "Pending"? As of now, I have the following:
Does anyone know of a control or a way to render a group of object relationships like visio? Right now I just have them sitting inside nested divs, but it's not as slick as everything being connected with lines in a flow
I'm a newbie to this so bear with me. From what I've read online LINQ to Entity should see the relationships without having to specify the joins between multiple tables. I have a relationship that goes across 4 tables Employee, EmployeeDepartmentLink, EmployeeProjectLink, and Project. The idea is an employee can be in multiple departments and work on multiple projects with it being specified which department the employee is in for that project.
This is a C# MVC3 program connecting to a SQL database using VS 2010 Express.
I have no problem with running this query to find employees on a project:
[Code]....
Tring to do the reverse, finding projects that an employee worked on results in an error:
[Code]....
Error message: The specified type member 'EmployeeDepartmentLinks' is not supported in LINQ to Entities. Only initializers, entity members, and entity navigation properties are supported. So I have 2 questions,
1) Why would it work in one direction and not the other? I've played around with it for a couple days with the same results.
2) Does it matter that my primary key and foreign keys are not named the same since all the relationships are connected in SQL? Ex: in Employee (EmployeePK)--(EmployeeFK) in EmployeeDepartmentLink Trying different stuff in LINQPad I was able to get the 2nd query to work if I specified all the joins which I thought was not neccesary with LINQ to Entity. I converted an SQL query that I made on the server into a LINQ query below which works.
I would like to ask a plain and simple question about the Model-View-Controller architecture - should the UML Class diagram for my application include all the controllers and views and their relationships, or should it just include my model classes, i.e. the entities that are the heart of the application, you know - like in an ordinary application - i.e. User, Administrator, Student, Teacher, Course, Grade etc...?
This is my first attempt at updating a database using LINQtoSQL. At least, it's my first if you don't count the tutorials I've followed. Unfortunately, The tutorials that I have found don't offer much more than updating a single table. I'm attempting to update a DB Model that's a bit more complex.
I am just getting started with entity framework with asp.net 3.5 using VS 2008
There are two tables, Categories & Subcategories:
Category table: CID, CategoryName Sub Category table: SID, CID, SubCategoryName I would like to get SID, CID, CategoryName, SubCategoryName in the gridview. Just as we write a select statement i.eSelect a.sid, b.cid, b.categoryname, b.subcategoryname from subcategories a inner join categories b on a.cid=b.cid & put the same in a gridview.
I was trying for the whole day & couldnt get atleast one url that would teach how to do it.
I have a table that contains item data. If the item is a particular type further information exists to describe the item. The additional information isn't that heavy however the number of records in relation to the main file will be quite small (less than 5%).
So I have 2 scenarios:1) Put the additional data in the main table and take tha hit on storage
2) Create an additional table and link the 2 together
If we were talking huge amounts of data I can understand that 2) would be the obvious choice but given the simplicity should 1) be a consideration?
If 2) is the answer - is it possible to create a dependency between the 2 tables when the item is 'that' particular type. In other words wnsure the addition data is populated for the required items and not others.
I am having a problem mapping a many-to-one relationship from an abstract base class mapping to a concrete union-subclass. Example:
public abstract class Entity { public virtual Guid ID {get; set;} public virtual string Name {get;set;} public virtual User OwnerUser {get; set;} }
public class User : Entity { public virtual string UserName {get; set;} }
I have a base abstract class for all of my database objects. I am mapping these classes with the Entity class as the abstract mapping class and the User as a union-subclass. When creating the configuration object, no errors are thrown and the Schema exports just fine. However, the field to the OwnerUser just won't show up in the database for all of the concrete classes. Here is an example of how the mapping looks
I am also using an Oracle XE instance as the database backend. If this isn't enough information to properly answer the question, let me know and I will add what I can.
I've been reading up on DDD a little bit, and I am confused how this would fit in when using an ORM like NHibernate. Right now I have a .NET MVC application with fairly "fat" controllers, and I'm trying to figure out how best to fix that. Moving this business logic into the model layer would be the best way to do this, but I am unsure how one would do that.
My application is set up so that NHibernate's session is managed by an HttpModule (gets session / transaction out of my way), which is used by repositories that return the entity objects (Think S#arp arch... turns out a really duplicated a lot of their functionality in this). These repositories are used by DataServices, which right now are just wrappers around the Repositories (one-to-one mapping between them, e.g. UserDataService takes a UserRepository, or actually a Repository). These DataServices right now only ensure that data annotations decorating the entity classes are checked when saving / updating.
In this way, my entities are really just data objects, but do not contain any real logic. While I could put some things in the entity classes (e.g. an "Approve" method), when that action needs to do something like sending an e-mail, or touching other non-related objects, or, for instance, checking to see if there are any users that have the same e-mail before approving, etc., then the entity would need access to other repositories, etc. Injecting these with an IoC wouldn't work with NHibernate, so you'd have to use a factory pattern I'm assuming to get these. I don't see how you would mock those in tests though......................
