I need some help with MVC architecture. I use the following architecture for an object named User.
UserRepository -> IUserRepository -> UserService -> IUserService -> UserController
The User object comes from my database and I'm using EntityFramework. I have a function that returns a list of users Return_All_Users(). One of the fields that gets returned is "UserType". This comes out as a number, but when I show the list in my Index.aspx page, I would like it to show as a string. The number for "UserType" needs to look into a Dictionary to find the string that goes along with the number like "Administrator" and I would like this string to show in my Index page.
How would I go about doing this? I'm currently using this function:
public IEnumerable<User> Return_All_Users()
{
//my code here
}
I had another post for a similar question, and it was suggested that my IEnumerable should return a string, not the User object. I tried that, but then I'm working with a Dynamic model and I didn't want to do that. Nor do I know how to work with a Dynamic model, so I thought maybe there is a better way of doing this.
Should this happen in my UserService? Maybe I need to create a new class called NewUser, and define the UserType as a string, then instantiate a new NewUser and pass the value from User. Before the UserType is passed, I would look in the dictionary and get the correct value for the key.
Should I do that, or is there a better way?
After I posted this question, I just thought of doing this with a stored procedure. Maybe use a stored procedure in my database to return the data, as opposed to looking up my data straight from my database table.
I would create a View Model UserView that was formatted to the representation of how your view would best use that data. You could perform the mapping from User to UserView within your Repository or Controller depending on where you prefer doing this kind of mapping.
Related
Detail
I am developing web application in asp.net core with Identity. now in my application I have two kind of user. Customer and Partner both have different profile information and login scenario.customer can login from simple signup from web page but partner can signup from different view with different mandatory fields.
Problem
How can I design Schema.
what are the good practices in this case.
What are the drawback.
Code
This is what I have done so far
public class ApplicationUser : IdentityUser
{
public CustomerProfile CustomerProfile { get; set; }
}
Use inheritance:
public class ApplicationUser : IdentityUser {}
public class Customer : ApplicationUser
{
// Customer-specific properties
}
public class Partner : ApplicationUser
{
// Partner-specific properties
}
By default, this will be implemented via STI (single-table inheritance). That means you'll have just your standard AspNetUsers table containing columns for the properties on ApplicationUser and all derived types. A discriminator column will be added to indicate which type was actually saved, which will then be used to instantiate the right type when queried.
For the most part, this works just fine. The one downside is that properties on derived classes must be nullable. The reason is simple: it would be impossible to provide values for Customer columns while saving a Partner and vice versa. However, the properties only need be nullable at the database-level. You can still require that they be set in forms and such via a view model.
The alternative is to use TPT (table-per-type). With this approach, you'll get AspNetUsers, but also Customers and Partners tables as well. However, the tables for the derived types will have columns corresponding only to the properties specific to that type and a foreign key back to AspNetUsers. All common properties are stored there. With this, you can now enforce columns have values at the database-level, but querying users will require a join. To use TPT, you simply add the Table attribute to your class, i.e. [Table("Customers")] and [Table("Partners")], respectively.
The one important thing to keep in mind with using inheritance, though, is that you need to work with the type you actually want to be persisted. If you save an ApplicationUser instance, it will be an ApplicationUser, not a Customer or Partner. In this regard, you need to be careful with using the correct types with things like UserManager which generically reference the user type. Even if you create an instance of Customer, if you save it via an instance of UserManager<ApplicationUser>, it will upcast to ApplicationUser and that is what will be persisted. To create a new Customer, you'll need an instance of UserManager<Customer>. Likewise, for partners.
However, this also works to your benefit, as if you attempt to look up a user from an instance of UserManager<Customer> for example, you will only find them if they are in fact a Customer. In this way, it makes it trivially simple to have separate portals where only one or the other can log in, as you've indicated that you want.
public String addStudent( #ModelAttribute("HelloWeb")Student student, ModelMap model){
}
can somebody explain how does this work?
what is the use of ModelMap model?
ModelMap subclasses LinkedHashMap.
public class ModelMap extends LinkedHashMap{
}
Model is an interface. ModelMap is an implementation of the Model interface.
Basically when you have data in code and you want to make that data available to the rendering of your jsp page, you need to put that data somewhere so that it is available. That is what a Model is for. To hold that data you retrieved in your code. It is just a glorified map.
So example, I have a form with a backing object with data. The form has three drop downs that I also need data to fill the drop downs. That is 4 different objects. 3 Lists for the drop downs and one object for the form backing object.
If my code gets all this data, I put them into the Model's Map and now I can use them on my jsp page.
refer this for more info.
also refer here for detailed info.
An architecture pattern followed in web applications is MVC which stands for Model, View And Controller.
Model holds the data. View is your display and Controller controls the flow.
A model is generally a simple object which can be rendered on screen. For example, a simple update user preferences will hold data which can be contained in a domain or model object called as user.
However, when the views and interactions get complex, a simple object may not suffice. And a complex object is needed. This somewhat complex object contains some other objects. For example, a page like user's news feed dashboard may have to hold data about;
user (name, etc) held in some user object
user's preferences held in userpreference object which in turn can be part of user
Some other objects - which may are not very suitable to be contained in the user object itself.
Basically, all these objects can make the model somewhat complex. So for better organization, these can be stored as name value pairs and packaged inside a single Map. So the page can refer to the required keys and get the object it needs to render.
ModelMap is this kind of a container object
I am using MVC3 and EF4 to write a web application. I am using an action header like below to capture the form values submitted by the user.
<HttpPost()>
Public Function Edit(ByVal prod as Product) As ActionResult
I use the below code for updating the record.
db.Attach(prod)
db.ObjectStateManager.ChangeObjectState(prod, EntityState.Modified)
db.SaveChanges()
I get the submitted values in prod object which I update in the database. The problem is that there are some users who are not allowed to modify certain fields in a Product, say ProductCost. I have disabled the textboxes for such fields in the HTML. But since it is clientside, the user can easily enable it using some tool like Firebug and modify the value.
The only solution I could come up was to retrieve the existing record from the database and copy its ProductCost value into prod.ProductCost. But I don't like firing a query for achieving this. Is there a better way to achieve this?
Edit: I found the below link to update particular fields. How to update only one field using Entity Framework?
You can use the below code to modify a particular field.
context.ObjectStateManager.GetObjectStateEntry(user).SetModifiedProperty("FieldName");
Now the question is do I have to write the above statement for every field the user is able to modify? If yes, suppose the Product model has 10 fields (1 primary key) and the user is allowed to modify all of them except the primary key, I need to write 9 statements?? Is there a method where you can specify multiple properties at once. Or even better something where you specify the properties which are not modified. (Note: I know I can run a loop over an array of field names to avoid writing 9 statements. I am asking for an alternative method and not refactoring the above)
Never trust client data. Always have your server code to validate the input and do appropriate actions.
I would create separate overloads of my Respiratory method update the product in different ways and then check what is the current user's access type, If he is admin, i will call the overload which updates everything, if he is a manager, i will call the method which updates name,imageUrl and price and if he is an employee, i will call the method which updates only name and ImageURL
[HttpPost]
public ActionResult Edit(Product prod)
{
if(ModelState.IsValid)
{
string userType=GetCurrentUserTypeFromSomeWhere();
if(userType=="admin")
{
repo.UpdateProduct(prod);
}
else if(userType=="manager")
{
repo.UpdateProduct(prod.ID, prod.Name, prod.ImageUrl, prod.Price);
}
else if(userType=="employee")
{
repo.UpdateProduct(prod.ID, prod.Name, prod.ImageUrl);
}
return RedirectToAction("Updated",new {id=prod.ID});
}
}
I have a table called Code in my LINQ to SQL datacontext. I also have a class called Codes in my Models folder. What I want to do is save the updated object Codes to my database table Code. Is this possible?
In my controller, I would pass the edited Object to my Model. My CodesRepository file contains this:
public Codes EditCode(Codes CodeToEdit)
{
private EventsDataContext _db = new EventsDataContext();
Codes C = new Codes();
C = CodeToEdit;
_db.Codes.InsertOnSubmit(C); //error here, something about invalid arguments
//InsertOnSubmit is for adding a new object, but I don't know the syntax
// for editing an existing object.
_db.SubmitChanges();
}
This is probably not the correct way of doing this so can someone point me in the right direction? Do I even need a class called Codes or do I need to somehow just use my database table? Thanks.
Solution: I decided to change from Linq to SQL to an Entity Framework and it works much better. This way, I don't have to define my Codes class since it comes straight from the database and I was able to delete the Codes class file.
You should use DataContext.Attach when you get an object back that corresponds to en existing row in the database. For Linq-to-sql's optimistic concurrency handling to work this requires that you either have the original, unsaved object available, or that you have a TimeStamp column in the database. The latter is preferred, as it only requires one extra field to be handled (probably through a hidden field in the web form).
So I have read some of the similar asked questions, but I don't know if the right questions were asked. It appears there are different ways to get data from multiple entities passed into your View Model, but I want to go about it the correct way.
I basically have 2 entities available in my controller, and I need to pass different information from both entities to my view. I have read about creating a SomeNameViewModel class that would be instantiated in my controller ViewResult method. With the SomeNameViewModel object assigning the data into a single object to pass to the View Model
Example:
public ViewResult List()
{
var vm = new SomeNameViewModel {
products = _prodRepo.All();
catName = <Some Expression>;
return View(vm);
}
But is this the best practice way to go about this?
I am using Nhibernate: So would this be better handled in my Fluent Mapping so that I have access to the other entity through the one-to-one mapping?
Using a model per view is a common (and good) way to go about providing data to your views. View models can encompass values from more than one entity type and may contain ancillary data as well. You might want to also consider using view-specific models for any entities contained in your view model to further isolate your view from your domain objects. This way you can provide to your view exactly the data they need and no more and, if your domain model changes, you may be able to only modify how the view-specific model gets updated from the domain model rather than propagating the change throughout your views.