MVVM and DBContext - how to put it together? - wpf

Question

I'm trying to follow the MVVM pattern, however I spent some good time on this issue, googled a lot and checked stackoverflow as well... No working example found so far.
Basically, I've a simple application and want to retrieve and write data to SQL server. Here's my code:
//Model
public class Visitor
{
public string ID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
}
//ViewModel
public class VisitorViewModel : ViewModelBase
{
public ObservableCollection<Visitor> _visitorDataCollection = new ObservableCollection<Visitor>();
public ObservableCollection<Visitor> VisitorDataCollection
{
get { return _visitorDataCollection; }
set { _visitorDataCollection = value; }
}
private string _firstName = "";
private string _lastName = "";
public string FirstName
{
get { return _firstName; }
set
{
if (value != _firstName)
{
_firstName = value;
OnPropertyChanged("FirstName");
}
}
}
public string LastName
{
get { return _lastName; }
set
{
if (value != _lastName)
{
_lastName = value;
OnPropertyChanged("LastName");
}
}
}
public VisitorViewModel()
{
}
}
}
//VisitorContext class that represents a database context
public partial class VisitorContext : DbContext
{
public VisitorContext()
: base()
{
}
public DbSet<VISITOR> Visitors { get; set; }
}
}
Nothing really fancy. However, I cannot put it "together". How to complete that to retrieve all visitors and add a new one?
Could someone point me to the right direction?

Answer 1

Just a simple example how make it all to life.
Add some commands to VM:
public ICommand Add {get; private set;}
In constructor:
public VisitorViewModel()
{
using(var context = new VisitorContext())
{
//fill collection with initial data from DbContext
context.Visitors.ToList().ForEach(_visitorDataCollection.Add);
}
//setup add command, here I'm using MVVM Light like you
Add = new RelayCommand(()=> {
using(var context = new VisitorContext())
{
_visitorDataCollection.Add(context.Visitors.Add(new Visitor {
FirstName = this.FirstName,
LastName = this.LastName //read values from model properties
});
}
});
}
That's it, all you need to do is bind this ViewModel to appropriate View.