select all checkbox binding in mvvm - wpf

Question

I am working on 'Select All' checkbox in datagrid header in wpf using mvvm pattern. On clicking the checkbox, all the checkboxes gets checked and on uncheking it, the reverse happens.
But I am unable to fetch and bind the selected items to the View Model.
My code is like this
<DataGrid Grid.Row="0" Background="LightGray" CanUserAddRows="False" AutoGenerateColumns="False" HorizontalAlignment="Left" Name="dataGridCustomers" ItemsSource="{Binding Path=UsecaseListItems}" CanUserResizeRows="False">
<DataGrid.Columns>
<DataGridTemplateColumn >
<DataGridTemplateColumn.Header>
<CheckBox x:Name="headerCheckBox" IsChecked="{Binding Path=MainWindowViewModel.AllSelected, Mode=TwoWay,
UpdateSourceTrigger=PropertyChanged}" Command="{Binding DoStuffCommand}" CommandParameter="{Binding ElementName=UserCaseListControl}"/>
</DataGridTemplateColumn.Header>
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<CheckBox Name="chkSelectAll" HorizontalAlignment="Center" IsChecked="{Binding IsChecked, ElementName=headerCheckBox, Mode=OneWay}" />
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>
<DataGridTextColumn Binding="{Binding Path=UsecaseName}" Header="UsecaseName" IsReadOnly="True" >
<DataGridColumn.HeaderStyle>
<Style TargetType="DataGridColumnHeader">
<Setter Property="FontWeight" Value="Bold"/>
</Style>
</DataGridColumn.HeaderStyle>
</DataGridTextColumn>
ViewModel is like:
private bool _IsSelected;
public bool IsSelected
{
get { return _IsSelected; }
set
{
_IsSelected = value;
OnPropertyChanged("IsSelected");
}
}
private bool _AllSelected;
public bool AllSelected
{
get { return _AllSelected; }
set
{
_AllSelected = value;
foreach (var reportListItemModel in UsecaseListItems)
{
reportListItemModel.IsSelected = this._AllSelected;
OnPropertyChanged("IsSelected");
}
OnPropertyChanged("AllSelected");
}
}
private ObservableCollection<UseCase> _usecaseListItems = new ObservableCollection<UseCase>();
public ObservableCollection<UseCase> UsecaseListItems
{
get { return _usecaseListItems; }
set {
_usecaseListItems = value;
OnPropertyChanged("UsecaseListItems");
}
}

Answer 1

With your code, there will be no direct binding of selected items. As all your checkboxes were bind to headerCheckBox.IsChecked.
You could bind to your UsecaseListItem.IsSelected instead, and find another way to to execute selectAll:
e.g. Define the UseCase that inherit ObservableObject and use your above code in AllSelected to change each item's IsSelected property.
Or use a Command (for example) in your headerCheckBox.