MVVM data binding to new object instance - silverlight

Question

I'm using MVVMlight in windows phone. The model is bound via xaml through the locator. The view model loads a new instance of the model from a webrequest then assigns it. I'm not sure why the view is not being updated, is it because its a new instance being assigned? If I update a property of the model instead of assigning a new instance, it updates on the view.
How do I update the view when assigning a new instance of the model?
View Model:
public class MyViewModel : ViewModelBase
{
public MyModel Model { get; set; }
public MyViewModel ()
{
if (IsInDesignMode)
{
}
else
{
//async call
api.GetModel(response =>
Deployment.Current.Dispatcher.BeginInvoke
(() =>
{
//this works.
//Model.Property1 = "Some Text";
//this doesn't work
Model = response.Data;
}
));
}
}
}
View.xaml
<UserControl x:Class="Grik.WindowsPhone.CardDetailsView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
DataContext="{Binding MyModel, Source={StaticResource Locator}}" >
<Grid x:Name="LayoutRoot" >
<TextBlock Text="{Binding Model.Property1}" />
</Grid>
</UserControl>

Answer 1

I would like to see your code in View Model Locator class
In MyViewModel class you may need to rewrite this property
public MyModel Model { get; set; }
to
private MyModel _model;
public MyModel Model {
get{return this._model;}
set{
this._model = value;
this.NotifyPropertyChanged("Model");
}
}

Answer 2

the ViewModel does not implement INotifyPropertyChanged interface.
The MyModel as well as all of its properties need to use the property changed event as well.
You show you use Model.Property1 in the xaml, Model.Property1 needs to also raise the property changed event.
public class MyModel : INotifyPropertyChanged
{
private string _Property1 = "";
public string Property1
{
get { return this._Property1; }
set
{
if (value != this._Property1)
{
this._Property1 = value;
NotifyPropertyChanged();
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}