public class Person
{
    public string Name { get; set; }

    public int Age { get; set; }
}

public class PersonViewModel
{
    private ObservableCollection<Person> _persons = new ObservableCollection<Person>();

    public ObservableCollection<Person> Persons
    {
        get { return _persons; }
        set { _persons = value; }
    }
}

<Window x:Class="TestWpfApplication.MainWindow" ...
        DataContext="{Binding RelativeSource={RelativeSource Self}}">
    <Grid>
        <DataGrid ItemsSource="{Binding PersonViewModel, Path=Persons}">
            <DataGrid.Columns>
                <DataGridTextColumn Header="Name" Binding="{Binding Name}"></DataGridTextColumn>
                <DataGridTextColumn Header="Age" Binding="{Binding Age}"></DataGridTextColumn>
            </DataGrid.Columns>
        </DataGrid>
    </Grid>
</Window>