Consume Service method in View-Model [WPF-MVVM] - wpf

Question

Hi try port my Winform app to WPF with MVVM. I use Caliburn Micro and MEF as IoC. I have service in external dll -> Pokec_Toolki.dll and this services use other external dll such as JSON.NET, HtmlAgilityPack..etc (third party libraries).
My service look like this:
public interface IPokecConnection
{
PokecAccount LogOn(string nick, string password);
bool LogOff(PokecAccount account);
}
[Export(typeof(IPokecConnection))]
public class PokecConnection : IPokecConnection
{
}
For my Service I create consumer for class PokecConnection, it is in the same assembly as Service:
[Export]
public class PokecConnectionConsumer
{
private readonly IPokecConnection _pokecConn;
[ImportingConstructor]
public PokecConnectionConsumer(IPokecConnection pokecConn)
{
_pokecConn = pokecConn;
}
public PokecAccount MethodWrapperForLogOn(string name, string password)
{
return _pokecConn.LogOn(name, password);
}
}
I have simple view with 2 textbox and 1 button. I bind event click of button with caliburn convention on view-model.
View:
<Button Micro:Message.Attach="[Event Click]=[Action LogOn(tbNick.Text,tbPassword.Text)]"
Content="Prihlás ma"
Width="100"
Grid.Row="2"
Height="25" Margin="4,4,4,4" />
I need consume service method in my view model. So in view-model I have this:
[Export(typeof(IShellViewModel))]
public class ShellViewModel : Screen, IShellViewModel, IDataErrorInfo
{
private PokecConnectionConsumer _connConsumer;
protected override void OnInitialize()
{
base.OnInitialize();
var mycatalog = new AssemblyCatalog(System.Reflection.Assembly.LoadFrom("Pokec_Toolkit.dll"));
var container = new CompositionContainer(mycatalog);
container.ComposeParts(this);
_connConsumer = container.GetExportedValue<PokecConnectionConsumer>();
}
//this method is bind on event click of button in view
public void LogOn(string nick, string password)
{
//call method LogOn from class PokecConnection in external dll through PokecConnectionConsumer
var accout = _connConsumer.MethodWrapperForLogOn(nick, password);
// in this place if account is not null, I need close this view and create new view MainView
//a send to the MainViewModel constructor as argument variable account
//some test
MessageBox.Show(accout.SessionId);
}
}
I have these question:
First, It is good create consumer
for service class in external dll?
In my case PokecConnectionConsumer
**and this class is in same assembly
as service class PokecConnection?
It is correct way to load external
assembly in view-model in method
OnInitialize?
It is correct call service method in
view-model?
It exist more suitable way how bind
method from external dll on view
control ? I need simple load external dll in wpf app with MVVM
and bind service method on controls
in views. What is the best way?
How can I close actual view and create new view, also activate this view. I need send as argument variable from view-model to another vie-model constructor.**
MY SOLUTION:
I create interface assembly and refer this assembly in external service dll and also in wpf app.
In bootstraper I load this assembly with reflection:
var catalog =
new AggregateCatalog(
AssemblySource.Instance.Select(x => new AssemblyCatalog(x)).OfType<ComposablePartCatalog>());
catalog.Catalogs.Add(
new AssemblyCatalog(string.Format(
CultureInfo.InvariantCulture, "{0}{1}", System.IO.Directory.GetCurrentDirectory(), #"\Pokec_Toolkit.dll")));
_container = new CompositionContainer(catalog);
Than I create conductor class:
public interface IShellViewModel
{
void ShowLogOnView();
void ShowMessengerView();
}
[Export(typeof(IShellViewModel))]
public class ShellViewModel : Conductor<IScreen>, IShellViewModel
{
public ShellViewModel()
{
ShowLogOnView();
}
public void ShowLogOnView()
{
ActivateItem(IoC.Get<LogOnViewModel>());
}
public void ShowMessengerView()
{
ActivateItem(IoC.Get<MessengerViewModel>());
}
}
And in view-model I have this:
[Export]
public class LogOnViewModel : Screen, IDataErrorInfo, ILogOnViewModel
{
[Import]
private IShellViewModel _shellViewModel;
[Import]
private IPokecConnection _pokecConn;
//this method is bind on event click of button
public void LogOn(string nick, string password)
{
//SHOW NEW WIEW
_shellViewModel.ShowMessengerView();
}
}

Answer 1

1) Yes, so that if the external dependency changes, you do not have to recompile your UI. Also it must be outside View/VM logic.
2) Not I am afraid. Create a separate service class for it.
3) Same, Create a separate service class for it and use within VM.
4) Well, you have to load a DLL anyway. So load it in the service class.