I'll show how to build a WPF application with MVVM pattern for 2D-Poliline with draggable vertexes.
PointViewModel.cs
public class PointViewModel: ViewModelBase
{
public PointViewModel(double x, double y)
{
this.Point = new Point(x, y);
}
private Point point;
public Point Point
{
get { return point; }
set
{
point = value;
OnPropertyChanged("Point");
}
}
}
The class ViewModelBase contains only an implementation of interface INotifyPropertyChanged. This is necessary for reflecting changes of the clr-property on the visual representation.
LineViewModel.cs
public class LineViewModel
{
public LineViewModel(PointViewModel start, PointViewModel end)
{
this.StartPoint = start;
this.EndPoint = end;
}
public PointViewModel StartPoint { get; set; }
public PointViewModel EndPoint { get; set; }
}
It has references to Points, so the changes will be received automatically.
MainViewModel.cs
public class MainViewModel
{
public MainViewModel()
{
this.Points = new List<PointViewModel>
{
new PointViewModel(30, 30),
new PointViewModel(60, 100),
new PointViewModel(50, 120)
};
this.Lines = this.Points.Zip(this.Points.Skip(1).Concat(this.Points.Take(1)),
(p1, p2) => new LineViewModel(p1, p2)).ToList();
}
public List<PointViewModel> Points { get; set; }
public List<LineViewModel> Lines { get; set; }
}
It contains a sample data of points and lines
MainVindow.xaml
<Window.Resources>
<ItemsPanelTemplate x:Key="CanvasPanelTemplate">
<Canvas/>
</ItemsPanelTemplate>
<Style x:Key="PointListBoxItem">
<Setter Property="Canvas.Left" Value="{Binding Point.X}"/>
<Setter Property="Canvas.Top" Value="{Binding Point.Y}"/>
</Style>
<DataTemplate x:Key="LineTemplate">
<Line X1="{Binding StartPoint.Point.X}" X2="{Binding EndPoint.Point.X}" Y1="{Binding StartPoint.Point.Y}" Y2="{Binding EndPoint.Point.Y}" Stroke="Blue"/>
</DataTemplate>
<DataTemplate x:Key="PointTemplate">
<view:PointView />
</DataTemplate>
</Window.Resources>
<Grid>
<ItemsControl ItemsSource="{Binding Lines}" ItemsPanel="{StaticResource CanvasPanelTemplate}" ItemTemplate="{StaticResource LineTemplate}"/>
<ItemsControl ItemsSource="{Binding Points}" ItemContainerStyle="{StaticResource PointListBoxItem}" ItemsPanel="{StaticResource CanvasPanelTemplate}"
ItemTemplate="{StaticResource PointTemplate}"/>
</Grid>
Here is a lot of tricks. First of all, these ItemsControls are based not on vertical StackPanel, but on Canvas. The ItemsControl of points applies a special container template with a goal to place items on necessary coordinates. But the ItemsControl of lines don't require such templates, and it is strange at some point. Two last DataTemplates are obvious.
PointView.xaml
<Ellipse Width="12" Height="12" Stroke="Red" Margin="-6,-6,0,0" Fill="Transparent"/>
Left and Top margins are equal to a half of the Width and the Height. We have a transparent Fill because this property doesn't have a default value and the events of mouse don't work.
That's almost all. Only drag-n-drop functionality remains.
PointView.xaml.cs
public partial class PointView : UserControl
{
public PointView()
{
InitializeComponent();
this.MouseLeftButtonDown += DragSource_MouseLeftButtonDown;
this.MouseMove += DragSource_MouseMove;
}
private bool isDraggingStarted;
private void DragSource_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
this.isDraggingStarted = true;
}
private void DragSource_MouseMove(object sender, MouseEventArgs e)
{
if (isDraggingStarted == true)
{
var vm = this.DataContext as PointViewModel;
var oldPoint = vm.Point;
DataObject data = new DataObject("Point", this.DataContext);
DragDropEffects effects = DragDrop.DoDragDrop(this, data, DragDropEffects.Move);
if (effects == DragDropEffects.None) //Drag cancelled
vm.Point = oldPoint;
this.isDraggingStarted = false;
}
}
MainVindow.xaml.cs
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
this.DataContext = new MainViewModel();
this.AllowDrop = true;
this.DragOver += DropTarget_DragOver;
}
private void DropTarget_DragOver(object sender, DragEventArgs e)
{
var vm = e.Data.GetData("Point") as PointViewModel;
if (vm != null)
vm.Point = e.GetPosition(this);
}
}
So your sample is done using 2 xaml files and 3 viewmodels.
