Data Binding
When displaying a map, you might also want to overlay some additional information. As we've previously seen (in the Introduction help topic) we can define this information statically in XAML. However, it would be much more practical to use the VisualizationLayer's data binding capabilities to dynamically load and display map markers.
The VisualizationLayer simulates functionality of the ItemsControl class so in order to display your map data dynamically you just have to treat the layer as a typical items control. This means you have to use its ItemsSource and ItemTemplate properties. You can also make a use of the ItemTemplateSelector property, in order to implement advanced visualization depending on the data item.
When using a custom visual in the ItemTemplate of the layer, there are several attached properties that can be used to position and display the marker on its proper place:
MapLayer.Location—Represents the latitude and the longitude of the map point.MapLayer.BaseZoomLevel—Represents the zoom level, for which the element should have its scale transformation equal to 1.MapLayer.ZoomRange—Represents the range of zoom levels for which the element should be visible.MapLayer.MinScale—Represents minimum scale factor which will be applied to the framework element when it hasBaseZoomLevelproperty set and we zoom out map control.MapLayer.MaxScale—Represents maximum scale factor which will be applied to the framework element when it hasBaseZoomLevelproperty set and we zoom in map control.
In order to provide the needed data to the visualization layer, you have to create a collection of business objects, which represent the desired data. The following example shows how to do this.
Defining the item model
public class MapItem : INotifyPropertyChanged, INotifyLocationChanged
{
private double baseZoomLevel = double.NaN;
private string caption = string.Empty;
private Location location = Location.Empty;
private ZoomRange zoomRange = ZoomRange.Empty;
public MapItem(
string caption,
Location location,
double baseZoomLevel,
ZoomRange zoomRange)
{
this.Caption = caption;
this.Location = location;
this.BaseZoomLevel = baseZoomLevel;
this.ZoomRange = zoomRange;
}
public event EventHandler<LocationChangedEventArgs> LocationChanged;
public event PropertyChangedEventHandler PropertyChanged;
public double BaseZoomLevel
{
get
{
return this.baseZoomLevel;
}
set
{
this.baseZoomLevel = value;
this.OnPropertyChanged("BaseZoomLevel");
}
}
public string Caption
{
get
{
return this.caption;
}
set
{
this.caption = value;
this.OnPropertyChanged("Caption");
}
}
public Location Location
{
get
{
return this.location;
}
set
{
var oldLocation = this.location;
this.location = value;
this.OnPropertyChanged("Location");
this.OnLocationChanged(oldLocation, this.location);
}
}
public ZoomRange ZoomRange
{
get
{
return this.zoomRange;
}
set
{
this.zoomRange = value;
this.OnPropertyChanged("ZoomRange");
}
}
private void OnPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
{
this.PropertyChanged(
this,
new PropertyChangedEventArgs(propertyName));
}
}
public void OnLocationChanged(Location oldLocation, Location newLocation)
{
if (LocationChanged != null)
{
LocationChanged(this, new LocationChangedEventArgs(oldLocation, newLocation));
}
}
}
Public Class MapItem
Implements INotifyPropertyChanged, INotifyLocationChanged
Private m_baseZoomLevel As Double = Double.NaN
Private m_caption As String = String.Empty
Private m_location As Location = Location.Empty
Private m_zoomRange As ZoomRange = ZoomRange.Empty
Public Sub New( _
caption As String, _
location As Location, _
baseZoomLevel As Double, _
zoomRange As ZoomRange)
Me.Caption = caption
Me.Location = location
Me.BaseZoomLevel = baseZoomLevel
Me.ZoomRange = zoomRange
End Sub
Public Event LocationChanged As EventHandler(Of LocationChangedEventArgs) _
Implements INotifyLocationChanged.LocationChanged
Public Event PropertyChanged As PropertyChangedEventHandler _
Implements INotifyPropertyChanged.PropertyChanged
Public Property BaseZoomLevel() As Double
Get
Return Me.m_baseZoomLevel
End Get
Set(value As Double)
Me.m_baseZoomLevel = value
Me.OnPropertyChanged("BaseZoomLevel")
End Set
End Property
Public Property Caption() As String
Get
Return Me.m_caption
End Get
Set(value As String)
Me.m_caption = value
Me.OnPropertyChanged("Caption")
End Set
End Property
Public Property Location() As Location
Get
Return Me.m_location
End Get
Set(value As Location)
Dim oldLocation = Me.m_location
Me.m_location = value
Me.OnPropertyChanged("Location")
Me.OnLocationChanged(oldLocation, Me.m_location)
End Set
End Property
Public Property ZoomRange() As ZoomRange
Get
Return Me.m_zoomRange
End Get
Set(value As ZoomRange)
Me.m_zoomRange = value
Me.OnPropertyChanged("ZoomRange")
End Set
End Property
Private Sub OnPropertyChanged(propertyName As String)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
End Sub
Public Sub OnLocationChanged(oldLocation As Location, newLocation As Location)
RaiseEvent LocationChanged(Me, New LocationChangedEventArgs(oldLocation, newLocation))
End Sub
End Class
You can notice that the business class implements the
INotifyLocationChangedinterface. This is necessary in order to properly support runtime changes of theLocationproperty.
Defining the ItemTemplate and binding the attached properties
<telerik:RadMap x:Name="radMap"
ZoomLevel="8"
Center="42.6957539183824, 23.3327663758679">
<telerik:RadMap.Provider>
<telerik:OpenStreetMapProvider />
</telerik:RadMap.Provider>
<telerik:VisualizationLayer x:Name="visualizationLayer">
<telerik:VisualizationLayer.ItemTemplate>
<DataTemplate>
<Grid telerik:MapLayer.Location="{Binding Location}"
telerik:MapLayer.BaseZoomLevel="{Binding BaseZoomLevel}"
telerik:MapLayer.ZoomRange="{Binding ZoomRange}"
telerik:MapLayer.MaxScale="8"
HorizontalAlignment="Center"
VerticalAlignment="Center">
<Ellipse x:Name="PART_Ellipse"
Width="20"
Height="20"
Stroke="Red"
StrokeThickness="3"
Fill="Transparent">
<ToolTipService.ToolTip>
<ToolTip Content="{Binding Caption}" />
</ToolTipService.ToolTip>
</Ellipse>
</Grid>
</DataTemplate>
</telerik:VisualizationLayer.ItemTemplate>
</telerik:VisualizationLayer>
</telerik:RadMap>
Setting up the items source
public partial class Example: Window
{
public Example()
{
InitializeComponent();
this.visualizationLayer.ItemsSource = this.GetMapData();
}
private ObservableCollection<MapItem> GetMapData()
{
ObservableCollection<MapItem> data = new ObservableCollection<MapItem>();
data.Add(
new MapItem(
"Sofia",
new Location(42.6957539183824, 23.3327663758679),
8,
new ZoomRange(5, 12)));
data.Add(
new MapItem(
"Plovdiv",
new Location(42.1429369264591, 24.7498095849434),
8,
new ZoomRange(5, 12)));
data.Add(
new MapItem(
"Burgas",
new Location(42.5131732087098, 27.4611884843576),
8,
new ZoomRange(5, 12)));
data.Add(
new MapItem(
"Varna",
new Location(43.2073941930888, 27.9275176988258),
8,
new ZoomRange(5, 12)));
return data;
}
}
Public Partial Class Example
Inherits Window
Public Sub New()
InitializeComponent()
Me.visualizationLayer.ItemsSource = Me.GetMapData()
End Sub
Private Function GetMapData() As ObservableCollection(Of MapItem)
Dim data As New ObservableCollection(Of MapItem)()
data.Add( _
New MapItem( _
"Sofia", _
New Location(42.6957539183824, 23.3327663758679), _
8, _
New ZoomRange(5, 12)))
data.Add( _
New MapItem( _
"Plovdiv", _
New Location(42.1429369264591, 24.7498095849434), _
8, _
New ZoomRange(5, 12)))
data.Add( _
New MapItem( _
"Burgas", _
New Location(42.5131732087098, 27.4611884843576), _
8, _
New ZoomRange(5, 12)))
data.Add( _
New MapItem( _
"Varna", _
New Location(43.2073941930888, 27.9275176988258), _
8, _
New ZoomRange(5, 12)))
Return data
End Function
End Class