Select All Check-box on a Data-grid in WPF? and get selected rows in View-model?

 <DataGrid>
        <DataGrid.Columns>
            <DataGridTemplateColumn>
                <DataGridTemplateColumn.Header>
                    <CheckBox Name="CheckALL" />
                </DataGridTemplateColumn.Header>
                <DataGridTemplateColumn.CellTemplate>
                    <DataTemplate>
                        <CheckBox Name="chkDiscontinue" IsChecked="{Binding Path=IsChecked, ElementName=CheckALL, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}"/>
                    </DataTemplate>
                </DataGridTemplateColumn.CellTemplate>
            </DataGridTemplateColumn>
        </DataGrid.Columns>
    </DataGrid>

I can click the header check-box and make all check-boxes selected, But Here, I need to Get all selected grids bind to 'IsChecked'