MVVM - How to wrap ViewModel in a ViewModel? - mvvm

Question

First of all, I have read this post and did not find the answer for my problem.
I am not sure if this is an aggregated Model class or an aggregated ViewModel class, but this is what I have:
In my WPF (with Prism) application, I have a view 'Filter Customers View' that connects to a service and requests a list of 'Customer' objects, based on a filter.
The list that is returned from the service is this :
List<CustomerDTO> FilteredCustomers;
And the CustomerDTO looks like this:
public class CustomerDTO
{
public Guid CustomerId;
public String Name;
public String Address;
public String PhoneNumber;
public OrderInfoDTO LastOrderInformation;
public List<OtherClass> ListOfSomething;
}
And the OrderInfoDTO looks like this:
public class OrderInfoDTO
{
public Guid OrderId;
public DateTime OrderDate;
public int NumberOfProducts;
public double TotalAmountSpent;
}
And the OtherClass looks like this:
public class OtherClass
{
public Guid Id;
public String SomeText;
}
As you can see - the customer might or might not have a 'Last Order',
I would like to wrap the 'CustomerDTO' object in a ViewModel,
so that I can bind it to the view.
This is what I thought of doing :
public class CustomerViewModel : NotificationObject
{
private CustomerDTO _customerDTO;
public CustomerViewModel(CustomerDTO customerDTO)
{
_customerDTO = customerDTO;
}
public Guid CustomerId
{
get { return _customerDTO.CustomerId; }
set { _customerDTO.CustomerId = value; RaisePropertyChanged("CustomerId "); }
}
public String Name
{
get { return _customerDTO.Name; }
set { _customerDTO.Name = value; RaisePropertyChanged("Name"); }
}
public String Address
{
get { return _customerDTO.Address; }
set { _customerDTO.Address = value; RaisePropertyChanged("Address"); }
}
public String PhoneNumber
{
get { return _customerDTO.PhoneNumber; }
set { _customerDTO.PhoneNumber= value; RaisePropertyChanged("PhoneNumber"); }
}
}
.
Questions:
First of all - is 'CustomerDTO' what is known as a Model ? And is 'OrderInfoDTO' also a Model ? and what about 'OtherClass' ?
How do I treat the 'OrderInfoDTO' in my CustomerViewModel class ? Do I create a 'ViewModel' for it also ? where do I create the 'OrderInfoDTO' view-model ??? What happens if now someone updates the customer and sets the 'OrderInfoDTO' value ?
How do I treat the list of 'OtherClass' in my CustomerViewModel class ? Do I create an ObservableCollection for it ? What happens if someone will want to delete an item in it or update an item in it or add an item to it ?

Answer 1

Think about it this way:
The View is your UI that you would bind elements from the View Model to using the {Binding Path=, Mode=TwoWay -- If you want to update based upon the user input
The Model is only the data, this could a record set, file, database records etc. So CustomerDTO and OrderInfoDTO are models.
The View Model is your link between the data (Model) and the UI (View). It will allow to you change the data so it's easier to present on the UI
You would need to use ObservableCollection in all instances where there's a list that could change in the background.
You don't need a view model for OrderInfoDTO unless you need a view to update that data. If you are presenting a CustomerDTO info with OrderInfoDTO in it, then making it a property of the CustomerDTO view model would be fine.