How to check all checkbox in datagrid when the checkbox in header column are checked during runtime?

This is my XAML code

  <DataGrid x:Name="missiongrid" >
     <DataGrid.Columns>

                    <DataGridTemplateColumn  Header="Mission type" Width="320">
                        <DataGridTemplateColumn.HeaderTemplate>
                            <DataTemplate>
                                <StackPanel Orientation="Horizontal">
                                    <CheckBox x:Name="UpCheckbox"  Margin="10,10,0,0" 
                                               Content="Name"
                                               Checked="UpCheckbox_Click" 
                                              >
                                </CheckBox>

                                </StackPanel>
                            </DataTemplate>
                        </DataGridTemplateColumn.HeaderTemplate>
                        <DataGridTemplateColumn.CellTemplate>
                            <DataTemplate>
                                <StackPanel Orientation="Horizontal">
                                    <CheckBox Name="standardCheckbox" Margin="10,10,0,0" IsChecked= "{Binding  Column1}" Checked="CheckBox_Click_1" Unchecked="UnCheckBox_Click_1"  />
                                    <TextBlock Text="{Binding  Column2}" Padding="10,5,0,0" HorizontalAlignment="Left" />
                                </StackPanel>
                            </DataTemplate>
                        </DataGridTemplateColumn.CellTemplate>

                    </DataGridTemplateColumn>

                    <DataGridTextColumn  Header="Location"  Binding="{Binding Column3}"/>

                </DataGrid.Columns>
</Datagrid>

I want all the checkbox in standardcheckbox to check when the Upcheckbox are checked during runtime. This is my code behind. Everything is run in a datagrid

myDataItems = new List<DataItem>();
myDataItems.Add(new DataItem { Column1 = true, Column2 = "Gambler", Column3 = "Jurassic Park", Column4 = "CasinoRoyal", Column5 = "JohnGramer" });
            myDataItems.Add(new DataItem { Column1 = true, Column2 = "Gambler",  Column3 = "Lord of the Ring", Column4 = "CasinoRoyal", Column5 = "JohnGramer" });
enter code here
            myDataItems.Add(new DataItem { Column1 = false, Column2 = "Gambler",  Column3 = "Harry potter", Column4 = "CasinoRoyal", Column5 = "JohnGramer" });
missiongrid.ItemsSource = myDataItems;

I try to add in this onCheck method, which is call when the checkbox is checked.

private void UpCheckbox_Click(object sender, RoutedEventArgs e)
    {


        for (int i = 0; i < myDataItems.Count; i++)
        {

            myDataItems[i].Column1 = true;// not working


        }

    }

But it is not working? The checkbox didnt change at all during runtime, only the header checkbox are checked

what should I do?