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Ninject bind property on view models to filter

I'm fairly new to ninject so you'll have to forgive the potentially stupid question. I have been able to successfully bind my own custom filter to controller actions, however my question is can I do the same to a property on a ViewModel? My scenario is thus:
I have a view model with properties that look like this
public class CreateViewModel
{
...
[PopulateWith(typeof(Country))]
public IEnumerable<SelectListItem> Countries { get; set; }
...
}
the attribute is is a simple class
public class PopulateWithAttribute : Attribute
{
public Type Type { get; }
public PopulateWithAttribute(Type t)
{
Type = t;
}
}
and all I want to be able to do is have a block of code that will run when a new instance of CreateViewModel is created, that will take the database context to hydrate the enumeration. I'm not sure if even an action filter is the correct route to go down like how you make custom authorization / logging functionality. It doesn't seem that the BindFilter<> has anything that points to being able to bind on properties...
A point in any direction or to any resources would be great.

Most efficient way to convert a object to another (Model to ViewModel)

Suppose I have a model with 20 fields, and in my index page, I want to list all models that are stored in my database.
In index page, instead of listing all fields of the model, I only to list 3 fields.
So, I make two class:
class CompleteModel {
public int Id { get; set; }
public string Field01 { get; set; }
public string Field02 { get; set; }
public string Field03 { get; set; }
public string Field04 { get; set; }
public string Field05 { get; set; }
...
public string Field20 { get; set; }
}
now, in my Controller, I can use:
await _context.CompleteModel.ToListAsync();
but I feel that it does not seem to be the right way to do it, because I'm getting all fields and using only 3 fields.
So, I made this code:
class ViewModel {
public string Field02 { get; set; }
public string Field04 { get; set; }
public string Field08 { get; set; }
}
var result = _context.CompleteModel.Select(
x => new {
x.Field02,
x.Field04,
x.Field08
}).ToListAsync();
var listResults = new List<IndexViewModel>();
if (result != null)
{
listResults.AddRange(results.Select(x => new IndexViewModel
{
Field02 = x.Field02,
Field04 = x.Field04,
Field08 = x.Field08
}));
}
I think this is a lot of code to do this.
First, I selected all the fields that I want, then, copied everything to another object.
There's a "more directly" way to do the same thing?
Like:
_context.CompleteModel.Select(x => new IndexViewModel { Field02, Field04, Field08 });

You could use AutoMapper to reduce the boiler plate so you're not manually copying field values over.
If you include the AutoMapper NuGet package then you'd need to have the following in your startup somewhere to configure it for your classes:
Mapper.Initialize(cfg => cfg.CreateMap<CompleteModel, ViewModel>());
You could then do something like the following:
var results = await _context.CompleteModel.ToListAsync();
var viewModelResults = results.Select(Mapper.Map<ViewModel>).ToList();
There are a lot of configuration options for the package so do take a look at the documentation to see if it suits your needs and determine the best way to use it if it does.

In my view this is one of the weaknesses of over abstraction and layering. The VM contains the data that is valuable to your application within the context of use (screen, process etc). The data model contains all the data that could be stored that might be relevant. At some point you need to match the two.
Use EF Projection to fetch only the data you need from the database into projected data model classes (using the EF POCO layer to define the query, but not to store the resultant data).
Map the projected classes onto your VM, if there is a naieve mapping, using Automapper or similar. However unless you are just writing CRUD screens a simple field by field mapping is of little value; the data you fetch from your data store via EF is in its raw, probably relational form. The data required by your VM is probably not going to fit that form very neatly (again, unless you are doing a simple CRUD form), so you are going to need to add some value by coding the relationship between the data store and the View Model.
I think concentrating on the count of lines of code would lead to the wrong approach. I think you can look at that code and ask "is it adding any value". If you can delegate the task to Automapper, then great; but your VM isn't really pulling its weight other than adding some validation annotation if you can consistently delegate the task of data model to VM data copying.

c# filter database results using EF similar to SQL WHERE Clause

I've connected to my database using Entity Framework and am building my first MVC app for use in a web page.
I can get the controller to populate public strings in my models with no problem... the issue I'm having is that I can't figure out how to filter responses from my database.
I expect to have only one item returned which I will display in the view with #Model.BusinessUnit
Here's my Model Class for the database table:
public partial class TBL_Wholesale_UWS_BusinessUnits
{
public int PrimaryID { get; set; }
public string BusinessUnit { get; set; }
public string Status { get; set; }
}
Here's what I have in my controller:
public ActionResult test(int PrimaryID)
{
var testing = new TBL_Wholesale_UWS_BusinessUnits();
// maybe putting new is the wrong thing to do as that would be wiping the class? IDK
return View(testing);
}
As you can see, the PrimaryID is passed to the controller via the querystring and this is recognised without issue, but I'm at a loss as to where to add the filter, I assumed it would be something like...
var testing = TBL_Wholesale_UWS_BusinessUnits.Where(TBL_Wholesale_UWS_BusinessUnits.PrimaryID = PrimaryID);`
but Visual Studio is telling me in no uncertain terms that this this wrong.
Had this been classic asp I would have just made a record set and used the where clause in SQL, but as this is built with the Entity Framework to do my connecting I don't really know where to start.
Any help would be greatly appreciated.

If you are only trying to return that one specific object to the view.. then you need to find that int PrimaryID in the database and retrieve that specific record.
What you are doing is simply creating a new instance of the TBL_Wholesale_UWS_BusinessUnits class which is empty.
Try this:
public ActionResult test(int PrimaryID)
{
var testing = db.TableName.Find(PrimaryID);
// db = Whatever the variable holding your connection string is.. maybe DbContext
// TableName = Whatever table in your database that holds the record you want
// This will return the specific object that you are looking for
return View(testing);
}
I hope this helps!

MVC - data calculations best practice - viewmodel vs. controller

rI need some advice on where to run a calculation on data.
I have a viewmodel that contains all the fields that I need for my calculation and I created the following for one of my calculations:
public class CommissionVM
{
public int? LoanAmountLock { get; set; } // from loan table
public decimal BranchRev { get; set; } // from revenue table
public decimal BranchProcessFee { get; set; } // from revenue table
public decimal BranchGrossTotal
{
get
{
return Convert.ToDecimal(LoanAmountLock * (BranchRev/ 100) + BranchProcessFee);
}
}
}
I tried to use the Model.BranchGrossTotal in my view, but it is returning 0. I think I have an order-of-operations problem. The values LoanAmountLock, BranchRev, and BranchProcessFee are returned as the results of a query:
public ActionResult Reconcile(int? id, string RevenueLoanType)
{
var model = new CommissionVM()
{
Loan = db.Loan.FirstOrDefault(a => a.id == id ),
BranchRevenues = db.BranchRevenues.FirstOrDefault(a => a.RevenueLoanType == RevenueLoanType),
};
return View(model);
}
I originally was able to get these calculations to work by doing all the math in the controller after I populate the viewmodel with the query, but there will be about 10 calculations, and from what I understand, I shouldn't clutter up my controller with business logic.
What is the best solution for this? Do I need to create another class for the calculations? If so, how do I populate that class with my data and use it in my controller?
EDIT: I am not sure how to set up the business classes and use them in the controller. Can anyone point me in the direction of a tutorial?

You should not do the calculation in your controller nor in your view model. You should do it in the Business Layer. Think about View Models are really simple classes that contain data to be displayed to the user, that's it.
Regarding the calculation, you should convert one of the terms to decimal, not the result of the calculation. If you divide integers, you get an integer.
You could create a class and call it CommissionService for example. That class should call your Data Layer to get the data, do any extra calculation and return the data (maybe a DTO) to the controller. The controller should create View Models based on the DTO and send them to the view.
Read these articles:
1) https://msdn.microsoft.com/en-us/library/hh404093.aspx
2) http://www.asp.net/mvc/overview/older-versions-1/models-%28data%29/validating-with-a-service-layer-cs
3) http://blog.diatomenterprises.com/asp-net-mvc-business-logic-as-a-separate-layer/
4) http://sampathloku.blogspot.com.ar/2012/10/how-to-use-viewmodel-with-aspnet-mvc.html

I don't like calculations on my view models -- you can't reuse the calculation easily elsewhere and it is harder to test and debug. Create separate classes to do business logic.
Your business logic classes can either return your view models or return values you use to populate those models. The trade-off is ease of use with reusability.
I generally favor returning the value rather than a big object so my services are more reusable.
Controller
public class BranchController : Controller
{
private IBusinessService service;
public BranchController()
{
this.service = new BusinessService(db);
}
public ActionResult Reconcile(int? id, string RevenueLoanType)
{
var model = new CommissionVM
{
BranchGrossTotal = this.service.GetBranchGrossTotal(id, RevenueLoanType),
...
};
return View(model);
}
}
Service
You can make any number of these and your controllers would use them as needed. If you need a query you should pass the DbContext instance or you may have problems with related entities on separate contexts.
public interface IBusinessService
{
decimal GetBranchGrossTotal(int id, string revenueLoanType);
}
public class BusinessService : IBusinessService
{
private DbContext db;
public BusinessService(DbContext db)
{
this.db = db;
}
public decimal GetBranchGrossTotal(int id, string revenueLoanType)
{
var branch = db.Branch.First(b => b.Id == id);
// do stuff
return total;
}
}
You could fully-populate and return a view model in your GetBranchGrossTotal() if you choose.

First of all, the properties you are assigning to your CommissionVM on your controller do not match the ones declared on your model. You assign Loan and BranchRevenues, when you have only LoanAmountLock and BranchRevs available on your model.
Please notice that the Loan property is an object itself, and the LoanAmountLock must be retrieved from this object (Loan.LoanAmountLock). The same happens with the BranchRevenues object. You should assign the BranchRevs to the respective property of the BranchRevenues object as needed. If you do not do this, then the values will default to 0 and when trying to calculate the BranchGrossTotal it will obviously be 0.
Another reason, assuming that you are correctly populating your model properties, is that the FirstOrDefault method, renders null values because there is no such entity. This will result also in the BranchGrossTotal to be 0.
You are right that you do not need to clutter your controller neither with calculations nor with db access. I would create a business class ComissionBusiness and instantiate it at the top of your controller. This class would have a method which performs all calculations. You should move the Reconcile method to your new business class method and call it on the reconcile action. Something like (excuse the lack of syntax)
public MyController : Controller {
public ComissionBusiness comissionBusiness;
public MyController(){
comissionBusiness = new ComissionBusiness();
}
public ActionResult Reconcile(int? id, string RevenueLoanType)
{
var model = comissionBusiness.Reconcile(id, revenueLoanType);
return View(model);
}
}

How to code/design the Model part in Caliburn.Micro?

I am new to MVVM pattern and Caliburn.Micro. I've read some tutorials on how to get started, but I'm confused about the Model part of MVVM in the context of Caliburn.
I want to create my first MVVM application and I have some design questions:
In tutorials, the Model was presented as simple property in
ViewModel. How should I manage more complex models? Is there any
naming convention? Obviously, there should be some external classes
made for my models, but how should I communicate between my models
and the view?
How should I keep references to many instances of one complex model?
For ex. cumtomers (instances of Customer model class)
Is there a possibility to manipulate one model class in many
ViewModels? How should I store my model reference, so it'll be
visible from different ViewModels?
Where should I put my code for more complex model manupulation/file,
database storage? How should I invoke such code? I'm not asking here
about SQLConnections, but MVVM best practices. :)
Thanks in advance for any help :)
EDIT:-------------------------------------------------------
Thank you for your anwser. I uderstand the topic more clearly, but I'm still confused about some details.
For an example, let's assume this little application. I have a form that allows me to add a new Customer. It has a few fields like Name, Surname etc.
After pressing the button, I invoke the addCustomer command in the ViewModel. I want my program to store the newly created customer inside the database.
My view also has the List control (whatever), which displays my customers as raw strings (like "Name: John, Surname: Doe, Address: ..." I know it's dumb to make it like this, but i need an example of model manipulation (like .toString()))
For this example, I've created a bunch of stuff to illustrate my vision of that process:
fields - it's a set of form fields like Name, Surname etc.
customerSet - it's a set of Customer class to store all created
customers
.addToDatabase(fields) - a method which puts newly created customer
to the database
.getStrings - a method which prepares a set of strings to be
displayed by the list in CustomerView
I think about 2 approaches that would be good for a solution:
First approach. I don't like this one. The only advantage is, that
ViewModel handles all the logic inside application. Sharing model
would be a serious problem here, because saving methods are bound to
the ViewModel class.
Second, MVC like approach. To me it's the most intuitive one. But - I
don't know where should I store CustomersModel object, so few
ViewModels could have access to it.
Which is the better one? Or maybe another approach that is more suitable for MVVM?
Another problem is: Where should I put my method that will load all the Customers from the database, so they could be displayes on the list? In "get method" inside viewmodel, or inside a model class?

In tutorials, the Model was presented as simple property in ViewModel.
How should I manage more complex models? Is there any naming
convention? Obviously, there should be some external classes made for
my models, but how should I communicate between my models and the
view?
Your models should represent whatever it is they need to whether it's a customer, account, etc. The view models job is to handle the interaction between the view and models.
How should I keep references to many instances of one complex model?
For ex. cumtomers (instances of Customer model class)
Generally, you will map complex models to more friendly format for display, you can do it manually or use a tool like AutoMapper.
Is there a possibility to manipulate one model class in many
ViewModels? How should I store my model reference, so it'll be visible
from different ViewModels?
If you're working with a local db you can pass IDs around. If it's a service you could persist the model locally for other view models to work with. You could also inject a singleton, ISharedData, into view models that need to work with shared data.
Where should I put my code for more complex model manupulation/file,
database storage? How should I invoke such code? I'm not asking here
about SQLConnections, but MVVM best practices. :)
Create services for more complex model manipulation / business logic. Inject the services into view models that require them. ICustomerService, IAccountService, etc.
EDIT:-------------------------------------------------------
You're first approach is correct. To your point about sharing the model being a serious problem because saving methods are bound to the view model class. The view model will have a SaveCustomerCommand that is fired when the button is clicked, because of its binding.
The SaveCustomerCommand will persist the CustomerModel, regardless of how the CustomerModel is persisted. So if its a database, the view model might have a reference to a context and issue a _db.Save(CustomerModel). If another view model needs to manipulate a CustomerModel, it will do so by using the context. The view model could also have a reference to a CustomerService that handles the crud for the CustomerModel.
Here's how this might look:
public class AddCustomerViewModel : Screen
{
private readonly ICustomerService _customerService;
public AddCustomerViewModel(ICustomerService customerService)
{
_customerService = customerService;
}
//If button is named x:Name="SaveCustomer" CM will
//bind it by convention to this method
public void SaveCustomer(Customer customer)
{
_customerService.Save(customer);
}
}
public class CustomerListViewModel : Screen
{
private readonly ICustomerService _customerService;
private List<CustomerDisplayModel> _customers;
public CustomerListViewModel(ICustomerService customerService)
{
_customerService = customerService;
}
public List<CustomerDisplayModel> Customers
{
get { return _customers; }
set
{
_customers = value;
NotifyOfPropertyChange();
}
}
//only fires once, unlike OnActivate()
protected override void OnInitialize()
{
var customers = _customerService.LoadAllCustomers();
//could just use the model but this shows how one might map from
//the domain model to a display model, AutoMapper could be used for this
Customers = customers.Select(c => new CustomerDisplayModel(c)).ToList();
}
}
public interface ICustomerService
{
List<Customer> LoadAllCustomers();
void Save(Customer customer);
}
//same as button, Label named x:Name="CustomerName" will bind
// to CustomerName
public class CustomerDisplayModel
{
private readonly Customer _customer;
public CustomerDisplayModel(Customer customer)
{
_customer = customer;
}
public string CustomerName
{
get { return _customer.Name; }
set { _customer.Name = value; }
}
public string Surname
{
get { return _customer.Surname; }
set { _customer.Surname = value; }
}
public string Address
{
get { return _customer.Address; }
set { _customer.Address = value; }
}
}
public class Customer
{
public int Id { get; set; }
public string Name { get; set; }
public string Surname { get; set; }
public string Address { get; set; }
}