DataGrid won't update ViewModel

Question

I've got a datagrid which is bound to an ObservableCollection of the ViewModel below. The Datagrid will display all values correctly, so the binding seems to be working, but if I change some value the Grid won't call the setter's of my VM. Could somebody tell me why?

Here's my ViewModel:

    public class DocumentVm : ViewModelBase
{
    private Document document;
    public bool IsNew { get; private set; }
    public Document Document {
        get { return document; }
    }

    public DocumentVm(Document document)
    {
        this.document = document;
        IsNew = false;
    }

    public DocumentVm(Document document, bool isNew)
    {
        this.document = document;
        IsNew = isNew;
    }

    public String Name 
    {
        get { return document.Name; }
        set { document.Name = value; RaisePropertyChangedEvent("Name");}
    }

    public String Path
    {
        get { return document.Path; }
        set { document.Path = value; }
    }

    public String Metadata
    {
        get { return document.Metadata; }
        set { document.Metadata = value; }
    }

    public int SpeechId
    {
        get { return document.SpeechId; }
        set { document.SpeechId = value; }
    }

}

Here is the XAML Code:

<DataGrid Margin="3" Grid.Row="7" Grid.Column="1" BorderThickness="0" 
      ItemsSource="{Binding Path=CurrentSpeech.Documents, Mode=TwoWay}" 
      SelectedItem="{Binding Path=CurrentSpeech.CurrentDocument, Mode=TwoWay}">
<DataGrid.Columns>
    <DataGridTemplateColumn Header="Name" Width="SizeToCells">
        <DataGridTemplateColumn.CellTemplate>
            <DataTemplate>
                <TextBox Text="{Binding Name, Mode=TwoWay}" />
            </DataTemplate>
        </DataGridTemplateColumn.CellTemplate>
    </DataGridTemplateColumn>
    <DataGridTemplateColumn Header="MetaDaten" Width="SizeToCells">
        <DataGridTemplateColumn.CellTemplate>
            <DataTemplate>
                <TextBox Text="{Binding Metadata, Mode=TwoWay}" />
            </DataTemplate>
        </DataGridTemplateColumn.CellTemplate>
    </DataGridTemplateColumn>
    <DataGridTemplateColumn Header="Pfad" Width="SizeToCells">
        <DataGridTemplateColumn.CellTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding Path}" />
            </DataTemplate>
        </DataGridTemplateColumn.CellTemplate>
    </DataGridTemplateColumn>
</DataGrid.Columns>

Thank you all!

Answer 1

UpdateSourceTrigger=PropertyChanged on the Bindings was missing.

Answer 2

Not sure why the setters aren't getting called but if you use dependency properties they actually do get called. I'm far too drunk to investigate why the CLR properties aren't getting set in your project but this works for me.

public partial class MainWindow : Window
{        public ObservableCollection<DocumentVm> Items
    {
        get { return (ObservableCollection<DocumentVm>)GetValue(ItemsProperty); }
        set { SetValue(ItemsProperty, value); }
    }
    public static readonly DependencyProperty ItemsProperty =
        DependencyProperty.Register("Items", typeof(ObservableCollection<DocumentVm>), typeof(MainWindow), new PropertyMetadata(null));

    public MainWindow()
    {
        InitializeComponent();
        Items = new ObservableCollection<DocumentVm>();
        Items.Add(new DocumentVm() { Name = "Name 1"});
        Items.Add(new DocumentVm() { Name = "Name 2"});
    }
}

public class DocumentVm : DependencyObject
{
    public string Name
    {
        get { return (string)GetValue(NameProperty); }
        set { SetValue(NameProperty, value); }
    }
    public static readonly DependencyProperty NameProperty =
        DependencyProperty.Register("Name", typeof(string), typeof(DocumentVm), new PropertyMetadata(null, new PropertyChangedCallback( (s, e)=>
            {
                // This will run when the property is set.
            })));        
}