this.DataContext is NULL? Use to be filled - Switched to Autofac - windows-phone-7

Question

I am using MVVM Light, Autofac for windows phone 7 and Autofac locator.
With autofac
http://www.nuget.org/packages/Autofac.Wp7
using GalaSoft.MvvmLight;
using GalaSoft.MvvmLight.Ioc;
using Microsoft.Practices.ServiceLocation;
using MvvmLight1.Model;
using Autofac;
namespace MvvmLight1.ViewModel
{
public class ViewModelLocator
{
static ViewModelLocator()
{
var builder = new ContainerBuilder();
builder.RegisterType<MainViewModel>();
var container = builder.Build();
ServiceLocator.SetLocatorProvider(() => new AutofacServiceLocator(container));
}
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance",
"CA1822:MarkMembersAsStatic",
Justification = "This non-static member is needed for data binding purposes.")]
public MainViewModel Main
{
get
{
return ServiceLocator.Current.GetInstance<MainViewModel>();
}
}
}
}
using Microsoft.Phone.Controls;
namespace MvvmLight1
{
public partial class MainPage : PhoneApplicationPage
{
// Constructor
public MainPage()
{
InitializeComponent();
var main = this.DataContext as MainPage; // will be null
}
}
}
<phone:PhoneApplicationPage x:Class="MvvmLight1.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:ignore="http://www.ignore.com"
mc:Ignorable="d ignore"
FontFamily="{StaticResource PhoneFontFamilyNormal}"
FontSize="{StaticResource PhoneFontSizeNormal}"
Foreground="{StaticResource PhoneForegroundBrush}"
SupportedOrientations="Portrait"
Orientation="Portrait"
d:DesignWidth="480"
d:DesignHeight="768"
shell:SystemTray.IsVisible="True"
DataContext="{Binding Main, Source={StaticResource Locator}}">
<!--LayoutRoot contains the root grid where all other page content is placed-->
<Grid x:Name="LayoutRoot"
Background="Transparent">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<!--TitlePanel contains the name of the application and page title-->
<StackPanel x:Name="TitlePanel"
Grid.Row="0"
Margin="24,24,0,12">
<TextBlock x:Name="ApplicationTitle"
Text="{Binding ApplicationTitle}"
Style="{StaticResource PhoneTextNormalStyle}" />
<TextBlock x:Name="PageTitle"
Text="{Binding PageName}"
Margin="-3,-8,0,0"
Style="{StaticResource PhoneTextTitle1Style}" />
</StackPanel>
<!--ContentPanel - place additional content here-->
<Grid x:Name="ContentGrid"
Grid.Row="1">
<TextBlock Text="{Binding WelcomeTitle}"
Style="{StaticResource PhoneTextNormalStyle}"
HorizontalAlignment="Center"
VerticalAlignment="Center"
FontSize="40"
TextWrapping="Wrap"
TextAlignment="Center" />
</Grid>
</Grid>
</phone:PhoneApplicationPage>
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using Autofac;
using Microsoft.Practices.ServiceLocation;
namespace MvvmLight1
{
public sealed class AutofacServiceLocator : ServiceLocatorImplBase
{
readonly IComponentContext _container;
public AutofacServiceLocator(IComponentContext container)
{
if (container == null)
throw new ArgumentNullException("container");
_container = container;
}
protected override object DoGetInstance(Type serviceType, string key)
{
return key != null ? _container.ResolveNamed(key, serviceType) : _container.Resolve(serviceType);
}
protected override IEnumerable<object> DoGetAllInstances(Type serviceType)
{
var enumerableType = typeof(IEnumerable<>).MakeGenericType(serviceType);
object instance = _container.Resolve(enumerableType);
return ((IEnumerable)instance).Cast<object>();
}
}
}
using GalaSoft.MvvmLight;
using MvvmLight1.Model;
namespace MvvmLight1.ViewModel
{
public class MainViewModel : ViewModelBase
{
public MainViewModel()
{
}
}
}
now the viewModel in my constructor of MainPage.cs will always be null.
When I just used SimpleIoc it was filled with the Main Object.