using System;

using System.Collections.Generic;

using System.Collections.ObjectModel;

using System.Diagnostics;

using System.Linq;

using System.Reflection;

using System.Text;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Data;

using System.Windows.Documents;

using System.Windows.Input;

using System.Windows.Media;

using System.Windows.Media.Imaging;

using System.Windows.Navigation;

using System.Windows.Shapes;

using GongSolutions.Wpf.DragDrop;

using GongSolutions.Wpf.DragDrop.Utilities;

using MahApps.Metro.Controls;

​

namespace CaptainRecommendUI

{

    /// <summary>

    /// Interaction logic for MainWindow.xaml

    /// </summary>

    public partial class MainWindow : MetroWindow

    {

        public static MainWindow Instance;

        public MainWindow()

        {

            InitializeComponent();

​

            Instance = this;

​

            for (int i = 0; i < 3; ++i)

            {

                TreeViewItem root = new TreeViewItem() {Header = "Root" + i};

                trvMenu.Items.Add(root);

                root.Items.Add(new TreeViewItem() {Header = "Son1"});

                root.Items.Add(new TreeViewItem() {Header = "Son2"});

                root.Items.Add(new TreeViewItem() {Header = "Son3"});

            }

​

            AllowMultiSelection(trvMenu);

​

            trvMenu.DataContext = new TreeViewDrop();

            TextBlock1.DataContext = new TreeViewDrop();

        }

    }

     // Write access to IsSelectionChangeActive from TreeView to force update when changing IsSelected in TreeViewItem

        private static readonly PropertyInfo IsSelectionChangeActiveProperty = typeof (TreeView).GetProperty

                (

                    "IsSelectionChangeActive",

                    BindingFlags.NonPublic | BindingFlags.Instance

                );

​

        // Allow multiple selection when Ctrl/Shift is down

        public static void AllowMultiSelection(TreeView treeView)

        {

            if (IsSelectionChangeActiveProperty == null) return;

​

            var selectedItems = new List<TreeViewItem>();

            treeView.SelectedItemChanged += (a, b) =>

            {

                var treeViewItem = treeView.SelectedItem as TreeViewItem;

                if (treeViewItem == null) return;

​

                var isSelectionChangeActive = IsSelectionChangeActiveProperty.GetValue(treeView, null);

​

                IsSelectionChangeActiveProperty.SetValue(treeView, true, null);

                if (Keyboard.IsKeyDown(Key.LeftCtrl) || Keyboard.IsKeyDown(Key.RightCtrl) ||

                    Keyboard.IsKeyDown(Key.LeftShift) || Keyboard.IsKeyDown(Key.RightShift))

                {

                    selectedItems.ForEach(item => item.IsSelected = true);

                }

                else

                {

                    selectedItems.ForEach(item => item.IsSelected = (item == treeViewItem));

                    selectedItems.Clear();

                }

​

                if (!selectedItems.Contains(treeViewItem))

                {

                    selectedItems.Add(treeViewItem);

                }

                else

                {

                    treeViewItem.IsSelected = false;

                    selectedItems.Remove(treeViewItem);

                }

​

                // Restore

                IsSelectionChangeActiveProperty.SetValue(treeView, isSelectionChangeActive, null);

            };

        }

}

​

public class TreeViewDrop : IDropTarget

    {

        public void DragOver(IDropInfo dropInfo)

        {

            Debug.WriteLine("DRAGOVER ");

​

            dropInfo.Effects = DragDropEffects.Move;

        }

​

        public void Drop(IDropInfo dropInfo)

        {

            MainWindow.Instance.TextBlock1.Background = new SolidColorBrush(Color.FromRgb(255, 255, 255));

            Debug.WriteLine("Drop ");

        }

}

​

<controls:MetroWindow 

    x:Class="CaptainRecommendUI.MainWindow" 

    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 

    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 

    xmlns:controls="http://metro.mahapps.com/winfx/xaml/controls"

    xmlns:dragDrop="clr-namespace:GongSolutions.Wpf.DragDrop;assembly=GongSolutions.Wpf.DragDrop"

    xmlns:captainRecommendUi="clr-namespace:CaptainRecommendUI"

    Title="MainWindow" Height="600" Width="700"

    BorderBrush="{DynamicResource AccentColorBrush}"

    BorderThickness="1"

    WindowStartupLocation="CenterScreen">

    <Grid>

        <Grid.ColumnDefinitions>

            <ColumnDefinition Width="200" />

            <ColumnDefinition Width="Auto" />

            <ColumnDefinition Width="Auto" />

        </Grid.ColumnDefinitions>

        <TreeView Name="trvMenu" AllowDrop="True"

                 dragDrop:DragDrop.IsDragSource="True">

            <TreeView.ItemTemplate>

                <HierarchicalDataTemplate ItemsSource="{Binding Items}">

                    <TextBlock Text="{Binding Title}" />

                </HierarchicalDataTemplate>

            </TreeView.ItemTemplate>

        </TreeView>

        <Grid Grid.Column="2">

            <Grid.RowDefinitions>

                <RowDefinition Height="50" />

                <RowDefinition Height="Auto" />

            </Grid.RowDefinitions>

            <TextBlock Grid.Row="0" Name="TextBlock1"

    Text="Hello! I am a Target." Foreground="Red"

                   dragDrop:DragDrop.IsDropTarget="True"

                   dragDrop:DragDrop.DropHandler="{Binding}">

            </TextBlock>

            <StackPanel Grid.Row="1"

                        Visibility="{Binding IsEmpty,Converter={StaticResource BooleanToVisibilityConverter}}"

                        VerticalAlignment="Center"

                        HorizontalAlignment="Center"

                        Orientation="Vertical">

                <Viewbox>

                <TextBlock  FontSize="100" HorizontalAlignment="Center" Margin="0 0 0 4" Text="}"/>

                </Viewbox>

​

                <TextBlock  FontSize="26" HorizontalAlignment="Center" Margin="0 0 0 4" Text="Drag items here"/>

                <!--<views:FileIcon BorderThickness="0" Width="50" Height="50" Foreground="{DynamicResource PrimaryHueMidBrush}"/>-->

                <TextBlock FontSize="26" Margin="0 4 0 0" Text="to get recommendations" HorizontalAlignment="Center"/>

            </StackPanel>

        </Grid>

    </Grid>

</controls:MetroWindow >

​