C# WPF Binding DataGrid to TabControl - wpf

Question

i´m a newbie in WPF and have a Problem with data-binding. I hope you can help me:
Here is my XAML- Code:
<Window x:Class="WpfApplication4.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<TabControl Name="MainTabControl" ItemsSource="{Binding}" Margin="2,0,-2,0">
<TabControl.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding Header}" Tag="{Binding Rid}" />
</StackPanel>
</DataTemplate>
</TabControl.ItemTemplate>
<TabControl.ContentTemplate>
<DataTemplate>
<DataGrid ItemsSource="{Binding Dg}" />
</DataTemplate>
</TabControl.ContentTemplate>
</TabControl>
</Grid>
</Window>
So i have a TabControl with a binding to a ObservableCollection of Tabs. Each Tab has a TextBlock as Header and a DataGrid.
Binding:
public MainWindow()
{
InitializeComponent();
DataGrid dg = new DataGrid();
DataGridTemplateColumn xx = new DataGridTemplateColumn()
{
Header = new TextBlock() { Text = "Edit", Tag = "Edit" }
};
xx.Width = new DataGridLength(1, DataGridLengthUnitType.Auto);
dg.Columns.Add(xx);
OCTabs.Add(new OCTab() { Header = "test1", Rid = 1 , Dg = dg});
OCTabs.Add(new OCTab() { Header = "test2", Rid = 2 , Dg = dg});
OCTabs.Add(new OCTab() { Header = "test3", Rid = 3, Dg = dg });
MainTabControl.DataContext = OCTabs;
}
and here the Tab- Class:
public class OCTab : INotifyPropertyChanged
{
private string _header;
private int _rid;
private DataGrid dg;
public DataGrid Dg { get { return dg; } set { dg = value; NotifyPropertyChanged("Dg"); } }
public string Header { get { return _header; } set { _header = value; NotifyPropertyChanged("Header"); } }
public int Rid { get { return _rid; } set { _rid = value; NotifyPropertyChanged("Rid"); } }
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
Now my problem:
everything works fine, except for the DataGrids from each Tab. The DataGrid is empty (no Columns,...)
The Binding doesn´t work and i don´t know why...
EDIT:
so is it possible, that each Tabitem has it´s own datagrid?