DataGrid checkall not working

Hi have a Datagrid with rowCheckBoxes and an header checkbox for checking all.

The header checkbox bind a method in MainViewModel who will update the property of my model data to true. But the checkboxes are still unchecked.

<DataGrid AutoGenerateColumns="False" x:Name="grdLignes" HorizontalAlignment="Stretch" Margin="0,0,0,0" 
                  VerticalAlignment="Stretch" CanUserAddRows="False" CanUserDeleteRows="False" Grid.ColumnSpan="2"
                  ItemsSource="{Binding CmLignes, UpdateSourceTrigger=PropertyChanged}">
            <DataGrid.Resources>
                <Style TargetType="{x:Type DataGridRow}">
                    <Style.Triggers>
                        <MultiDataTrigger>
                            <MultiDataTrigger.Conditions>
                                <Condition Binding="{Binding Path=hasLink, Mode=OneTime}" Value="True"/>
                            </MultiDataTrigger.Conditions>
                            <Setter Property="IsEnabled" Value="False"/>
                        </MultiDataTrigger>
                    </Style.Triggers>
                </Style>
            </DataGrid.Resources>
            <DataGrid.Columns>
                <DataGridTemplateColumn>
                    <DataGridTemplateColumn.Header>
                        <CheckBox Command="{Binding RelativeSource={RelativeSource AncestorType=Window, Mode=FindAncestor}, Path=DataContext.ToggleCheckAll}" CommandParameter="{Binding IsChecked, RelativeSource={RelativeSource Self}}"/>
                    </DataGridTemplateColumn.Header>
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <CheckBox Name="rowCheck" VerticalAlignment="Center" HorizontalAlignment="Center" IsChecked="{Binding Path=hasLink, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"/>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>
                <DataGridTextColumn Header="Ref Mag" Binding="{Binding Path=refMag}" IsReadOnly="True"/>
                <DataGridTextColumn Header="Ref Fourn" Binding="{Binding Path=refFourn}"/>
                <DataGridTextColumn Header="Désignation" Binding="{Binding Path=design}"/>
                <DataGridTextColumn Header="Quantité" Binding="{Binding Path=qte, StringFormat=N2}"/>
                <DataGridTemplateColumn Header="Fournisseur">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <!--<ComboBox ItemsSource="{Binding FournList, RelativeSource={RelativeSource AncestorType=Window}}" SelectedItem="{Binding Path=fourn}"/>-->
                            <ComboBox ItemsSource="{Binding Path=fournList}" SelectedItem="{Binding Path=selectedFourn, UpdateSourceTrigger=PropertyChanged}"/>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>
                <DataGridTextColumn Header="Fourn princ" Binding="{Binding Path=fournPrinc}" IsReadOnly="True"/>
                <DataGridTextColumn Header="Pièce" Binding="{Binding Path=numPiece}" IsReadOnly="True"/>
            </DataGrid.Columns>
        </DataGrid>

Then the MainViewModel:

public class MainViewModel : INotifyPropertyChanged
{
    private ContremarqueRepository cmRepos;

    private ObservableCollection<Contremarque> cmLignes;
    public ObservableCollection<Contremarque> CmLignes
    {
        get { return cmLignes; }
        set
        {
            cmLignes = value;
            OnPropertyChanged("CmLignes");
        }
    }
    public ICommand ToggleCheckAll { get; set; }
    public MainViewModel()
    {
        Collection<Contremarque> cms = cmRepos.getAll(doPiece);
        CmLignes = new ObservableCollection<Contremarque>(cms);

        ToggleCheckAll = new Command(ActionToggleCheckAll);
    }

    private void ActionToggleCheckAll(object param)
    {
        bool isChecked = (bool)param;
        if (isChecked)
        {
            foreach (Contremarque contremarque in CmLignes)
            {
                contremarque.hasLink = true;
            }
        }

        OnPropertyChanged("CmLignes");
    }
}

This is the Contremarque class:

public class Contremarque
{
    public bool hasLink { get; set; }
    public string refMag { get; set; }
    public string refFourn { get; set; }
    public string design { get; set; }
    public double qte { get; set; }
    public string fournPrinc { get; set; }
    public List<string> fournList { get; set; }
    public string selectedFourn { get; set; }
    public string numPiece { get; set; }

    public int dlNo;

    public override string ToString()
    {
        string str = string.Empty;
        foreach (var prop in this.GetType().GetProperties())
        {
            str += string.Format("{0} = {1} ", prop.Name, prop.GetValue(this, null));
        }

        return str;
    }
}

The propertyChanged should update the state of my checkboxes isn't it?