pmichna pmichna - 22 days ago 6
C# Question

How to do Drag and Drop in WPF in my "Metro Style" app?

I'm trying to create some primitive imitation of the Windows Metro style application. What I've done so far is adding new tiles to the window in

ObservableCollection
, I can change their color and remove them using
ContextMenu
. Now I want to do Drag and Drop with actual previewing the dragging (with semi transparent tile). I tried to do it by myself using many tutorials describing the DragDrop class in WPF but I have to admit I just can't understand it and I need help. I tried to follow: this tutorial. Here's a screenshot of my app: screenshot
And my code:

using System;
using System.Collections.Generic;
using System.Linq;
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 System.Collections.ObjectModel;

namespace Metro_Pawel_Michna
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
private ObservableCollection<myButton> _tiles = new ObservableCollection<myButton>();
Random r = new Random();
private int index = -1;
private List<Color> myColors = new List<Color>();
public MainWindow()
{
InitializeComponent();
this.DataContext = _tiles;
webBrowser.Visibility = Visibility.Collapsed;
btnClose.Visibility = Visibility.Collapsed;
myColors.Add(Colors.DarkCyan);
myColors.Add(Colors.Black);
myColors.Add(Colors.DarkGoldenrod);
myColors.Add(Colors.DarkBlue);
myColors.Add(Colors.DarkGray);
myColors.Add(Colors.DarkKhaki);
}

private void btnAdd_Click(object sender, RoutedEventArgs e)
{
myButton b = new myButton();
b.Content = txtUrl.Text;
b.MouseDoubleClick += new MouseButtonEventHandler(tileDbl_Click);
b.MouseRightButtonUp += new MouseButtonEventHandler(b_MouseRightButtonUp);

Color random = new Color();
int losuj = r.Next(6);
b.colorIndex = losuj;

random = myColors.ElementAt(losuj);

LinearGradientBrush lgb = new LinearGradientBrush(Colors.White, random, 45);
lgb.StartPoint = new Point(-0.5,-0.5);
lgb.EndPoint = new Point(1, 1);
b.Background = lgb;
_tiles.Add(b);
}

private void tileDbl_Click(object sender, RoutedEventArgs e)
{
const string http = "http://";
const string https = "https://";
string address = (sender as Button).Content.ToString();

if (String.Compare(http, 0, address, 0, 6) == 0 && address.Length > 7) webBrowser.Navigate(address);
else if (String.Compare(https, 0, address, 0, 7) == 0 && address.Length > 8) webBrowser.Navigate(address);
else webBrowser.Navigate("http://www.google.com/search?q=" + address);

tilesBox.Visibility = Visibility.Collapsed;
btnClose.Visibility = Visibility.Visible;
txtUrl.Visibility = Visibility.Collapsed;
btnAdd.Visibility = Visibility.Collapsed;
toolbar.HorizontalAlignment = HorizontalAlignment.Right;
webBrowser.Visibility = Visibility.Visible;
}

private void btnClose_Click(object sender, RoutedEventArgs e)
{
tilesBox.Visibility = Visibility.Visible;
btnClose.Visibility = Visibility.Collapsed;
txtUrl.Visibility = Visibility.Visible;
btnAdd.Visibility = Visibility.Visible;
toolbar.HorizontalAlignment = HorizontalAlignment.Left;
webBrowser.Visibility = Visibility.Collapsed;
}

private void Remove_Click(object sender, RoutedEventArgs e)
{
_tiles.RemoveAt(index);
}

private void b_MouseRightButtonUp(object sender, RoutedEventArgs e)
{
index = _tiles.IndexOf(sender as myButton);
}

private void ChangeColor_Click(object sender, RoutedEventArgs e)
{
myButton b = _tiles.ElementAt(index);
LinearGradientBrush lgb;
if (b.colorIndex != myColors.Count - 1)
lgb = new LinearGradientBrush(Colors.White, myColors.ElementAt(++b.colorIndex), 45);
else
{
lgb = new LinearGradientBrush(Colors.White, myColors.ElementAt(0), 45);
b.colorIndex = 0;
}
lgb.StartPoint = new Point(-0.5, -0.5);
lgb.EndPoint = new Point(1, 1);
b.Background = lgb;
}
}
}


XAML:

<Window x:Class="Metro_Pawel_Michna.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:Metro_Pawel_Michna="clr-namespace:Metro_Pawel_Michna"
Title="MainWindow" Height="350" Width="525" MinWidth="180" MinHeight="200">
<DockPanel LastChildFill="True">
<ToolBarTray Name="toolbar" DockPanel.Dock="Top">
<ToolBar>
<TextBox Name="txtUrl">Type an URL</TextBox>
<Button Name="btnAdd" Click="btnAdd_Click">Add</Button>
<Button Name="btnClose" Click="btnClose_Click">Close</Button>
</ToolBar>
</ToolBarTray>
<WebBrowser Height="auto" Name="webBrowser" Width="auto" />
<ScrollViewer>
<ItemsControl Name="tilesBox" ItemsSource="{Binding}">
<ItemsControl.ContextMenu>
<ContextMenu Name="contextMenu">
<MenuItem Header="Remove" Click="Remove_Click"/>
<MenuItem Header="Change color" Click="ChangeColor_Click"/>
</ContextMenu>
</ItemsControl.ContextMenu>
<ItemsControl.Resources>
<Style TargetType="{x:Type Metro_Pawel_Michna:myButton}">
<Setter Property="Width" Value="120"/>
<Setter Property="Height" Value="120"/>
<Setter Property="Margin" Value="10"/>
<Setter Property="Foreground" Value="White" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<Grid>
<Rectangle Fill="{TemplateBinding Background}" />
<ContentPresenter Content="{Binding Path=Content, RelativeSource={RelativeSource TemplatedParent}}" VerticalAlignment="Center" HorizontalAlignment="Center" />
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</ItemsControl.Resources>

<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
</ItemsControl>
</ScrollViewer>

</DockPanel>

</Window>

Answer

You can try to use some Drag & Drop framework to implement this functionality, like gong-wpf-dragdrop -

The GongSolutions.Wpf.DragDrop library is a drag'n'drop framework for WPF. It has the following features:

  • Works with MVVM : the logic for the drag and drop can be placed in a ViewModel. No code needs to be placed in codebehind, instead attached properties are used to bind to a drag handler/drop handler in a ViewModel.
  • Works with multiple selections.
  • Can drag data within the same control to re-order, or between controls.

http://code.google.com/p/gong-wpf-dragdrop/

reordering is what you are looking for...

In case you don't want to use any framework then I would suggest you to go through these articles -

How can I drag and drop items between data bound ItemsControls? || WayBack Link

http://www.codeproject.com/Articles/37161/WPF-Drag-and-Drop-Smorgasbord

and go through source code of some controls implementing drag & drop -

Drag and Drop Controls