问如何从WPF后面的代码中访问XAML按钮

EN

 <DataGrid  HorizontalAlignment="Stretch" ScrollViewer.HorizontalScrollBarVisibility="Hidden"  BorderBrush="#83D744" IsSynchronizedWithCurrentItem="False" VerticalGridLinesBrush="Transparent" Grid.Column="0"   RowHeaderWidth="0" CanUserAddRows="False" AutoGenerateColumns="False"  x:Name="datagrid1" Margin="10,150,8,50" Background="Transparent" RowBackground="#FF494949"  VerticalContentAlignment="Center" HorizontalContentAlignment="Center" ItemsSource="{Binding}">
        <DataGrid.Resources>
            <Style TargetType="{x:Type DataGridColumnHeader}">
                <Setter Property="Background" Value="#83D744"/>
                <Setter Property="Opacity" Value="1"/>
                <Setter Property="Foreground" Value="White"/>
                <Setter Property="HorizontalContentAlignment" Value="Center" />
                <Setter Property="FontSize" Value="18"/>
                <Setter Property="FontFamily" Value="Arial"/>
                <Setter Property="Height" Value="50"/>
            </Style>


            <Style x:Key="TextInCellCenter" TargetType="{x:Type TextBlock}" >
                <Setter Property="TextAlignment" Value="Center"/>
            </Style>
            <Style TargetType="{x:Type TextBlock}" x:Key="RightAligElementStyle">
                <Setter Property="TextAlignment" Value="Right"/>
            </Style>
            <Style TargetType="{x:Type TextBlock}" x:Key="LeftAligElementStyle">
                <Setter Property="TextAlignment" Value="Left"/>
            </Style>
            <SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" 
       Color="Transparent"/>
        </DataGrid.Resources>


        <DataGrid.Columns >
            <DataGridTextColumn Binding="{Binding ProductName}"     ElementStyle="{StaticResource LeftAligElementStyle}"     Header="NAZIV ARTIKLA" MinWidth="350"    Foreground="White" FontSize="20" FontFamily="Verdana" />
            <DataGridTextColumn Binding="{Binding Quantity}"        ElementStyle="{StaticResource TextInCellCenter}"         Header="KOLIČINA"   MinWidth="200" Foreground="White"      FontSize="20" FontFamily="Verdana" />
        </DataGrid.Columns>

        <DataGrid.GroupStyle>
            <!-- Style for groups at top level. -->
            <GroupStyle>
                <GroupStyle.Panel>
                    <ItemsPanelTemplate>
                        <DataGridRowsPresenter/>
                    </ItemsPanelTemplate>
                </GroupStyle.Panel>
                <GroupStyle.ContainerStyle>
                    <Style TargetType="{x:Type GroupItem}">
                        <Setter Property="Template">
                            <Setter.Value>
                                <ControlTemplate TargetType="{x:Type GroupItem}">
                                    <Expander IsExpanded="True"  Background="Black" Opacity="0.7">
                                        <Expander.Header >
                                            <DockPanel Height="50" Margin="0,0,0,0"  Name="dockPanel" Width="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type DataGrid}}, Path=ActualWidth}">

                                                <Button Name="btnFinishOrder" DataContext="{Binding Items[0]}" Content="{Binding ButtonCaption}" Margin="0,0,55,5" DockPanel.Dock="Right" Click="BtnFinishOrder_OnClick" FontSize="12" BorderThickness="1.5" HorizontalAlignment="Left"  VerticalAlignment="Bottom"  HorizontalContentAlignment="Center" VerticalContentAlignment="Center"  Foreground="#83D744"  Background="Transparent"  BorderBrush="#83D744" Width="130"   Height="40">
                                                    <Button.Template>
                                                        <ControlTemplate TargetType="Button">
                                                            <Border BorderThickness="{TemplateBinding BorderThickness}"
                                                    BorderBrush=    "{TemplateBinding BorderBrush}"
                                                    Background=     "{TemplateBinding Background}">
                                                                <ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}" />
                                                            </Border>
                                                        </ControlTemplate>
                                                    </Button.Template>
                                                </Button>

                                                <Button Name="btnTakeIt" Click="BtnTakeIt_OnClick"  DataContext="{Binding Items[0]}" Content="{Binding ButtonCaption}" Margin="0,0,20,5" DockPanel.Dock="Right" FontSize="12" BorderThickness="1.5" HorizontalAlignment="Left"  VerticalAlignment="Bottom"  HorizontalContentAlignment="Center" VerticalContentAlignment="Center"  Foreground="#83D744"  Background="Transparent"  BorderBrush="#83D744" Width="130"   Height="40">
                                                    <Button.Template>
                                                        <ControlTemplate TargetType="Button">
                                                            <Border BorderThickness="{TemplateBinding BorderThickness}"
                                                    BorderBrush="{TemplateBinding BorderBrush}"
                                                    Background="{TemplateBinding Background}">
                                                                <ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}" />
                                                            </Border>
                                                        </ControlTemplate>
                                                    </Button.Template>
                                                </Button>
                                                <TextBlock FontWeight="Normal" FontFamily="Verdana" FontSize="20" Height="25" Foreground="#83D744" Text="{Binding Items[0].ProductName}" />

                                            </DockPanel>
                                        </Expander.Header>
                                        <Expander.Content>
                                            <ItemsPresenter />
                                        </Expander.Content>
                                    </Expander>
                                </ControlTemplate>
                            </Setter.Value>
                        </Setter>
                    </Style>
                </GroupStyle.ContainerStyle>
            </GroupStyle>
        </DataGrid.GroupStyle>
        </DataGrid>

public partial class MainWindow : Window
{
    private ICollectionView view;
    private ObservableCollection<Product> ordersList;
    public MainWindow()
    {
        InitializeComponent();
        this.WindowStartupLocation = WindowStartupLocation.CenterScreen;
        this.WindowState = WindowState.Maximized;

        ordersList = new ObservableCollection<Product>()
        {
            new Product()
            {
                ProductName = "Prodct",
                Quantity = 1,
                NumberOfOrder = 100,
                IsInProgress = true,
                ButtonCaption = "Take it"
            },
            new Product()
            {
                ProductName = "Prodct1",
                Quantity = 2,
                NumberOfOrder = 1000,
                ButtonCaption = "Take it"

            },
            new Product()
            {
                ProductName = "Prodct2",
                Quantity = 3,
                NumberOfOrder = 10000,
                ButtonCaption = "Take it"

            },
            new Product()
            {
                ProductName = "Prodct3",
                Quantity = 4,
                NumberOfOrder = 100000,
                ButtonCaption = "Take it"

            },
        };

        view = CollectionViewSource.GetDefaultView(ordersList);

        view.GroupDescriptions.Add(new PropertyGroupDescription("NumberOfOrder"));
        DataContext = view;

        DispatcherTimer timer = new DispatcherTimer();
        timer.Interval = TimeSpan.FromSeconds(20);
        timer.Tick += Timer_Tick; ;
        timer.Start();
    }

    private void Timer_Tick(object sender, EventArgs e)
    {
        foreach (var item in ordersList)
        {
            if (item.IsInProgress)
            {
                item.ButtonCaption = "Order is Still in progress";
            }
        }
    }

    private void BtnFinishOrder_OnClick(object sender, RoutedEventArgs e)
    {
        throw new NotImplementedException();
    }

    private void BtnTakeIt_OnClick(object sender, RoutedEventArgs e)
    {
        Button b = sender as Button;

        Product prod = b.DataContext as Product;

        b.BorderBrush = null;
        prod.ButtonCaption = "Order is in progress";
        b.FontSize = 12;
    }
}

class Product:INotifyPropertyChanged
{
    private string productName;

    public string ProductName
    {
        get { return productName ; }
        set
        {
            productName = value ;
            OnPropertyChanged("ProductName");
        }
    }

    private int quantity;

    public int Quantity
    {
        get { return quantity; }
        set
        {
            quantity = value;
            OnPropertyChanged("Quantity");
        }
    }

    public int NumberOfOrder { get; set; }

    public bool IsInProgress { get; set; }

    private string buttonCaption;

    public string ButtonCaption
    {
        get { return buttonCaption; }
        set
        {
            buttonCaption = value;
            OnPropertyChanged("ButtonCaption");
        }
    }


    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}