/// <summary>
/// Tries to construct the view model using the argument. If that fails, it will try to use
/// the default constructor of the view model. If that is not available, <c>null</c> is returned.
/// </summary>
/// <param name="injectionObject">The object that is injected into the view model constructor.</param>
/// <param name="viewModelType">Type of the view model.</param>
/// <returns>Constructed view model or <c>null</c> if the view model could not be constructed.</returns>
/// <exception cref="ArgumentNullException">The <paramref name="viewModelType"/> is <c>null</c>.</exception>
private IViewModel ConstructViewModelUsingArgumentOrDefaultConstructor(object injectionObject, Type viewModelType)
{
Argument.IsNotNull("viewModelType", viewModelType);
if (ViewModelBehavior == LogicViewModelBehavior.Injected)
{
return(ViewModel);
}
if (PreventViewModelCreation)
{
Log.Info("ViewModel construction is prevented by the PreventViewModelCreation property");
return(null);
}
if (IgnoreNullDataContext && (injectionObject == null))
{
Log.Info("ViewModel construction is prevented by the IgnoreNullDataContext property");
return(null);
}
var determineViewModelInstanceHandler = DetermineViewModelInstance;
if (determineViewModelInstanceHandler != null)
{
var determineViewModelInstanceEventArgs = new DetermineViewModelInstanceEventArgs(injectionObject);
determineViewModelInstanceHandler(this, determineViewModelInstanceEventArgs);
if (determineViewModelInstanceEventArgs.ViewModel != null)
{
var viewModel = determineViewModelInstanceEventArgs.ViewModel;
Log.Info("ViewModel instance is overriden by the DetermineViewModelInstance event, using view model of type '{0}'", viewModel.GetType().Name);
return(viewModel);
}
if (determineViewModelInstanceEventArgs.DoNotCreateViewModel)
{
Log.Info("ViewModel construction is prevented by the DetermineViewModelInstance event (DoNotCreateViewModel is set to true)");
return(null);
}
}
var determineViewModelTypeHandler = DetermineViewModelType;
if (determineViewModelTypeHandler != null)
{
var determineViewModelTypeEventArgs = new DetermineViewModelTypeEventArgs(injectionObject);
determineViewModelTypeHandler(this, determineViewModelTypeEventArgs);
if (determineViewModelTypeEventArgs.ViewModelType != null)
{
Log.Info("ViewModelType is overriden by the DetermineViewModelType event, using '{0}' instead of '{1}'",
determineViewModelTypeEventArgs.ViewModelType.FullName, viewModelType.FullName);
viewModelType = determineViewModelTypeEventArgs.ViewModelType;
}
}
var injectionObjectAsViewModel = injectionObject as IViewModel;
if (injectionObjectAsViewModel != null)
{
var injectionObjectViewModelType = injectionObject.GetType();
if (ViewModelFactory.CanReuseViewModel(TargetViewType, viewModelType, injectionObjectViewModelType, injectionObject as IViewModel))
{
Log.Info("DataContext of type '{0}' is allowed to be reused by view '{1}', using the current DataContext as view model",
viewModelType.FullName, TargetViewType.FullName);
return((IViewModel)injectionObject);
}
}
Log.Debug("Using IViewModelFactory '{0}' to instantiate the view model", ViewModelFactory.GetType().FullName);
var viewModelInstance = ViewModelFactory.CreateViewModel(viewModelType, injectionObject);
Log.Debug("Used IViewModelFactory to instantiate view model, the factory did{0} return a valid view model",
(viewModelInstance != null) ? string.Empty : " NOT");
return(viewModelInstance);
}