how to set header checkbox checked all row checkbox checked in datagrid in wpf

hi,

   I want know how to  set header checkbox checked all row checkbox checked  and also unchecked means all row checkbox will be unchecked.. i passed datagrid values from sql server...

XAML code...

<GroupBox Header="Payslip Details" Name="lvpayslipdetails" Margin="0,66,0,36">
            <grid:DataGrid x:Name="lvpayslip" x:Uid="MyDataGrid" AutoGenerateColumns="False"
AlternationCount="1" SelectionMode="Single" ItemsSource="{Binding Path=Table}" IsReadOnly="True" HeadersVisibility="Column" FontSize="14" >

                <grid:DataGrid.Columns>
                    <grid:DataGridTemplateColumn>
                        <grid:DataGridTemplateColumn.Header>
                            <CheckBox IsChecked="{Binding IsSelected, Mode=TwoWay}" Name="chkheader" Click="chkheader_Click" />
                        </grid:DataGridTemplateColumn.Header>
                        <grid:DataGridTemplateColumn.CellTemplate>
                            <DataTemplate>
                                <CheckBox IsChecked="{Binding IsSelected, Mode=TwoWay}"  Margin="45 2 0 0" Name="chkrow" />
                            </DataTemplate>
                        </grid:DataGridTemplateColumn.CellTemplate>
                    </grid:DataGridTemplateColumn>
                    <grid:DataGridTextColumn Binding="{Binding Path=p_id}" IsReadOnly="True"
Header="P.Id" Width="0.7*" />

                    <grid:DataGridTextColumn Binding="{Binding Path=dbempname}"
Header="Emp Name" Width="2*" IsReadOnly="True" />
                    <grid:DataGridTextColumn Binding="{Binding Path=pmonth}"
Header="Month" Width="0.9*" IsReadOnly="True" />
                    <grid:DataGridTextColumn Binding="{Binding Path=pyear}"
Header="Year" Width="0.5*" IsReadOnly="True" />                    
                    <grid:DataGridTextColumn Binding="{Binding Path=gross,StringFormat=0.00}"
Header="Gross" Width="1*" IsReadOnly="True" />


                    <grid:DataGridTextColumn Binding="{Binding Path=deduction,StringFormat=0.00}"
Header="Deduction" Width="1.5*" IsReadOnly="True" />

                    <grid:DataGridTextColumn Binding="{Binding Path=netpay,StringFormat=0.00}"
Header="Net Pay" Width="1.3*" IsReadOnly="True" />

                    <grid:DataGridTemplateColumn Header="View Profile" Width="0.9*">

                        <grid:DataGridTemplateColumn.CellTemplate>

                            <DataTemplate>

                                <Button Content="View">

                                </Button>

                            </DataTemplate>

                        </grid:DataGridTemplateColumn.CellTemplate>

                    </grid:DataGridTemplateColumn>


                </grid:DataGrid.Columns>

            </grid:DataGrid>

        </GroupBox>

 C# coding...

public payslip()
        {
            InitializeComponent();
            
        }
        SqlConnection con;
        public bool flag;
        string cn = ConfigurationManager.AppSettings["cc"];
     
        public void viewleave()
        {
            con = new SqlConnection(cn);
            con.Open();
            SqlCommand cmd = new SqlCommand("lvpayslip", con);
            cmd.CommandType = CommandType.StoredProcedure;
            DataTable dt = new DataTable();
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            da.Fill(dt);
            lvpayslip.DataContext = dt.DefaultView;
            con.Close();
        }

        private void UserControl_Loaded(object sender, RoutedEventArgs e)
        {
            viewleave();
        }

private void chkheader_Click(object sender, RoutedEventArgs e)
        {
           //i dont know how check and uncheck the checkbox..
        }