MVVM Support

The Telerik RadChart control can be used with great success with the Model-View-ViewModel (MVVM) pattern. This tutorial will demonstrate how to use the MVVM pattern to get a better control over the colors of the bars of a single series.

  • Create a new class named Person, which implements the INotifyPropertyChanged interface.

public class Person : INotifyPropertyChanged 
{ 
    private double grade; 
    private string _name; 
    public string Name 
    { 
        get 
        { 
            return _name; 
        } 
        private set 
        { 
            _name = value; 
        } 
    } 
    public double Grade 
    { 
        get 
        { 
            return this.grade; 
        } 
        set 
        { 
            this.grade = value; 
            this.OnPropertyChanged( "Grade" ); 
        } 
    } 
    public Person( string name, double grade ) 
    { 
        Name = name; 
        Grade = grade; 
    } 
    public event PropertyChangedEventHandler PropertyChanged; 
    protected virtual void OnPropertyChanged( string propertyName ) 
    { 
        if ( this.PropertyChanged != null ) 
            this.PropertyChanged( this, new PropertyChangedEventArgs( propertyName ) ); 
    } 
} 
Public Class Person 
    Implements INotifyPropertyChanged 
    Private m_grade As Double 
    Private _name As String 
 
    Public Property Name() As String 
        Get 
            Return _name 
        End Get 
        Private Set(ByVal value As String) 
            _name = value 
        End Set 
    End Property 
 
    Public Property Grade() As Double 
        Get 
            Return Me.m_grade 
        End Get 
        Set(ByVal value As Double) 
            Me.m_grade = value 
            Me.OnPropertyChanged("Grade") 
        End Set 
    End Property 
 
    Public Sub New(ByVal name__1 As String, ByVal grade__2 As Double) 
        Name = name__1 
        Grade = grade__2 
    End Sub 
 
    Protected Overridable Sub OnPropertyChanged(ByVal propertyName As String) 
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName)) 
    End Sub 
 
    Public Event PropertyChanged(sender As Object, e As PropertyChangedEventArgs) Implements INotifyPropertyChanged.PropertyChanged 
End Class 

The class has two properties:

  • Name - will be displayed on the X axis.

  • Grade - will be displayed on the Y axis.

Create a new class named PersonViewModel, which implements the INotifyPropertyChanged interface. It will be used as an ItemsSource for the chart control.

public class PersonViewModel : INotifyPropertyChanged 
{ 
    private Person _person; 
    public Person Person 
    { 
        get 
        { 
            return _person; 
        } 
        private set 
        { 
            _person = value; 
        } 
    } 
    private Brush _gradeColor; 
    public Brush GradeColor 
    { 
        get 
        { 
            return _gradeColor; 
        } 
        private set 
        { 
            _gradeColor = value; 
        } 
    } 
    public PersonViewModel( Person person ) 
    { 
        this.Person = person; 
        person.PropertyChanged += HandleStudentPropertyChanged; 
        this.UpdateGradeColor(); 
    } 
    private void HandleStudentPropertyChanged( object sender, PropertyChangedEventArgs e ) 
    { 
        if ( e.PropertyName == "Grade" ) 
            this.UpdateGradeColor(); 
    } 
    private void UpdateGradeColor() 
    { 
        if ( this.Person.Grade < 10 ) 
            this.GradeColor = this.CreateBrush( "#FFFF3D40" ); 
        else if ( this.Person.Grade < 20 ) 
            this.GradeColor = this.CreateBrush( "#FFFD583A" ); 
        else if ( this.Person.Grade < 30 ) 
            this.GradeColor = this.CreateBrush( "#FFFD8145" ); 
        else if ( this.Person.Grade < 40 ) 
            this.GradeColor = this.CreateBrush( "#FFFAA03D" ); 
        else if ( this.Person.Grade < 50 ) 
            this.GradeColor = this.CreateBrush( "#FFFAC741" ); 
        else if ( this.Person.Grade < 60 ) 
            this.GradeColor = this.CreateBrush( "#FFFCED40" ); 
        else if ( this.Person.Grade < 70 ) 
            this.GradeColor = this.CreateBrush( "#FFD7FC3C" ); 
        else if ( this.Person.Grade < 80 ) 
            this.GradeColor = this.CreateBrush( "#FF99F839" ); 
        else if ( this.Person.Grade < 90 ) 
            this.GradeColor = this.CreateBrush( "#FF46E633" ); 
        else 
            this.GradeColor = this.CreateBrush( "#FF1CD64D" ); 
        this.OnPropertyChanged( "GradeColor" ); 
    } 
    public event PropertyChangedEventHandler PropertyChanged; 
    protected virtual void OnPropertyChanged( string propertyName ) 
    { 
        if ( this.PropertyChanged != null ) 
            this.PropertyChanged( this, new PropertyChangedEventArgs( propertyName ) ); 
    } 
    private Brush CreateBrush( string color ) 
    { 
        return new SolidColorBrush( this.GetColorFromHexString( color ) ); 
    } 
    private Color GetColorFromHexString( string s ) 
    { 
        s = s.Replace( "#", string.Empty ); 
        byte a = System.Convert.ToByte( s.Substring( 0, 2 ), 16 ); 
        byte r = System.Convert.ToByte( s.Substring( 2, 2 ), 16 ); 
        byte g = System.Convert.ToByte( s.Substring( 4, 2 ), 16 ); 
        byte b = System.Convert.ToByte( s.Substring( 6, 2 ), 16 ); 
        return Color.FromArgb( a, r, g, b ); 
    } 
} 
Public Class PersonViewModel 
    Implements INotifyPropertyChanged 
    Private _person As Person 
    Public Property Person() As Person 
        Get 
            Return _person 
        End Get 
        Private Set(ByVal value As Person) 
            _person = value 
        End Set 
    End Property 
 
    Private _gradeColor As Brush 
    Public Property GradeColor() As Brush 
        Get 
            Return _gradeColor 
        End Get 
        Private Set(ByVal value As Brush) 
            _gradeColor = value 
        End Set 
    End Property 
 
    Public Sub New(ByVal person As Person) 
        Me.Person = person 
        AddHandler person.PropertyChanged, AddressOf HandleStudentPropertyChanged 
        Me.UpdateGradeColor() 
    End Sub 
 
    Private Sub HandleStudentPropertyChanged(ByVal sender As Object, ByVal e As PropertyChangedEventArgs) 
        If e.PropertyName = "Grade" Then 
            Me.UpdateGradeColor() 
        End If 
    End Sub 
 
    Private Sub UpdateGradeColor() 
        If Me.Person.Grade < 10 Then 
            Me.GradeColor = Me.CreateBrush("#FFFF3D40") 
        ElseIf Me.Person.Grade < 20 Then 
            Me.GradeColor = Me.CreateBrush("#FFFD583A") 
        ElseIf Me.Person.Grade < 30 Then 
            Me.GradeColor = Me.CreateBrush("#FFFD8145") 
        ElseIf Me.Person.Grade < 40 Then 
            Me.GradeColor = Me.CreateBrush("#FFFAA03D") 
        ElseIf Me.Person.Grade < 50 Then 
            Me.GradeColor = Me.CreateBrush("#FFFAC741") 
        ElseIf Me.Person.Grade < 60 Then 
            Me.GradeColor = Me.CreateBrush("#FFFCED40") 
        ElseIf Me.Person.Grade < 70 Then 
            Me.GradeColor = Me.CreateBrush("#FFD7FC3C") 
        ElseIf Me.Person.Grade < 80 Then 
            Me.GradeColor = Me.CreateBrush("#FF99F839") 
        ElseIf Me.Person.Grade < 90 Then 
            Me.GradeColor = Me.CreateBrush("#FF46E633") 
        Else 
            Me.GradeColor = Me.CreateBrush("#FF1CD64D") 
        End If 
 
        Me.OnPropertyChanged("GradeColor") 
    End Sub 
 
    Protected Overridable Sub OnPropertyChanged(ByVal propertyName As String) 
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName)) 
    End Sub 
 
    Private Function CreateBrush(ByVal color As String) As Brush 
        Return New SolidColorBrush(Me.GetColorFromHexString(color)) 
    End Function 
 
    Private Function GetColorFromHexString(ByVal s As String) As Color 
        s = s.Replace("#", String.Empty) 
 
        Dim a As Byte = System.Convert.ToByte(s.Substring(0, 2), 16) 
        Dim r As Byte = System.Convert.ToByte(s.Substring(2, 2), 16) 
        Dim g As Byte = System.Convert.ToByte(s.Substring(4, 2), 16) 
        Dim b As Byte = System.Convert.ToByte(s.Substring(6, 2), 16) 
        Return Color.FromArgb(a, r, g, b) 
    End Function 
 
    Public Event PropertyChanged(sender As Object, e As PropertyChangedEventArgs) Implements INotifyPropertyChanged.PropertyChanged 
End Class 

The class has two properties:

  • A reference to a Person object.

  • GradeColor - the corresponding color of the referenced person.

There are a few helper methods. The UpdateGradeColor method is used to return a specific color, based on the person Grade property.

  • Add a new chart declaration to your XAML.

<telerik:RadChart x:Name="radChart" Margin="8"/> 
  • The chart will be built in the code-behind.

  • A BarChart will be used.

  • The Grade property will be displayed on the ordinate.

  • The Name property will be displayed on the absciss.

private void MVVM_Loaded( object sender, RoutedEventArgs e ) 
{ 
    radChart.DefaultView.ChartArea.AxisY.AutoRange = false; 
    radChart.DefaultView.ChartArea.AxisY.MinValue = 0; 
    radChart.DefaultView.ChartArea.AxisY.MaxValue = 100; 
    radChart.DefaultView.ChartArea.AxisY.Step = 10; 
    radChart.DefaultView.ChartLegend.Visibility = System.Windows.Visibility.Collapsed; 
    radChart.DefaultSeriesDefinition = new BarSeriesDefinition(); 
 
    SeriesMapping seriesMapping = new SeriesMapping(); 
    seriesMapping.ItemMappings.Add( new ItemMapping( "Person.Grade", DataPointMember.YValue ) ); 
    seriesMapping.ItemMappings.Add( new ItemMapping( "Person.Name", DataPointMember.XCategory ) ); 
    radChart.SeriesMappings.Add( seriesMapping ); 
    radChart.ItemsSource = this.GetData(); 
} 
Private Sub MVVM_Loaded(ByVal sender As Object, ByVal e As RoutedEventArgs) 
    radChart.DefaultView.ChartArea.AxisY.AutoRange = False 
    radChart.DefaultView.ChartArea.AxisY.MinValue = 0 
    radChart.DefaultView.ChartArea.AxisY.MaxValue = 100 
    radChart.DefaultView.ChartArea.AxisY.[Step] = 10 
 
    radChart.DefaultView.ChartLegend.Visibility = System.Windows.Visibility.Collapsed 
    radChart.DefaultSeriesDefinition = New BarSeriesDefinition() 
 
    Dim seriesMapping As New SeriesMapping() 
    seriesMapping.ItemMappings.Add(New ItemMapping("Person.Grade", DataPointMember.YValue)) 
    seriesMapping.ItemMappings.Add(New ItemMapping("Person.Name", DataPointMember.XCategory)) 
 
    radChart.SeriesMappings.Add(seriesMapping) 
    radChart.ItemsSource = Me.GetData() 
End Sub 

Here is the code for the GetData() method, which creates the mockup data:

private List<PersonViewModel> GetData() 
{ 
    Random rand = new Random( DateTime.Now.Millisecond ); 
    List<Person> studentList = new List<Person>(); 
    for ( int i = 0; i < rand.Next( 9, 12 ); i++ ) 
        studentList.Add( new Person( "Person" + i, rand.Next( 15, 100 ) ) ); 
    List<PersonViewModel> modelList = new List<PersonViewModel>(); 
    foreach ( Person person in studentList ) 
        modelList.Add( new PersonViewModel( person ) ); 
    return modelList; 
} 
Private Function GetData() As List(Of PersonViewModel) 
    Dim rand As Random = New Random(DateTime.Now.Millisecond) 
    Dim studentList As List(Of Person) = New List(Of Person) 
    Dim i As Integer = 0 
    Do While (i < rand.Next(9, 12)) 
        studentList.Add(New Person(("Person" + i), rand.Next(15, 100))) 
        i = (i + 1) 
    Loop 
 
    Dim modelList As List(Of PersonViewModel) = New List(Of PersonViewModel) 
    For Each person As Person In studentList 
        modelList.Add(New PersonViewModel(person)) 
    Next 
    Return modelList 
End Function 

The result so far can be seen on the image below:

  • The final step is to bind the GradeColor property of the PersonViewModel business object to the background of a single bar.

In order to change the background of each bar from the chart, you need to use the CreateItemStyleDelegate property of the RadChart. For more information read here.

Here is the method that will be passed to the delegate.

public Style BuildCustomItemStyle( Control item, Style style, DataPoint point, DataSeries dataSeries ) 
{ 
    if ( ( item as BaseChartItem ) == null ) 
    { 
        return style; 
    } 
    Style newStyle = new Style(); 
    newStyle.BasedOn = style; 
    newStyle.TargetType = typeof( Shape ); 
    Brush brush = ( dataSeries[ ( item as BaseChartItem ).CurrentIndex ].DataItem as PersonViewModel ).GradeColor; 
    newStyle.Setters.Add( new Setter( Shape.FillProperty, brush ) ); 
    return newStyle; 
} 
Public Function BuildCustomItemStyle(item As Control, style As Style, point As DataPoint, dataSeries As DataSeries) As Style 
    If TryCast(item, BaseChartItem) Is Nothing Then 
        Return style 
    End If 
    Dim newStyle As New Style() 
    newStyle.BasedOn = style 
    newStyle.TargetType = GetType(Shape) 
    Dim brush As Brush = TryCast(dataSeries(TryCast(item, BaseChartItem).CurrentIndex).DataItem, PersonViewModel).GradeColor 
    newStyle.Setters.Add(New Setter(Shape.FillProperty, brush)) 
    Return newStyle 
End Function 

To pass this method to the RadChart use its CustomItemStyleDelegate property.

this.radChart.CreateItemStyleDelegate = this.BuildCustomItemStyle; 
Me.radChart.CreateItemStyleDelegate = Me.BuildCustomItemStyle 

Set this property into the MVVM_Loaded handler.

Here is the final result:

Additionally you may want to remove the Background from the SeriesItemsLabels. This can be achieved by retemplating the default Style so that the Background applied to the Labels is Transparent and setting the Foreground to Black for example:

<Style x:Key="MySeriesItemLabel_Style" TargetType="telerik:SeriesItemLabel"> 
    <Setter Property="Padding" Value="2,0" /> 
    <Setter Property="Foreground" Value="Black"/> 
    <Setter Property="IsHitTestVisible" Value="False"/> 
    <Setter Property="ContentTemplate"> 
        <Setter.Value> 
            <DataTemplate> 
                <TextBlock Text="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=Content }" TextAlignment="Center" /> 
            </DataTemplate> 
        </Setter.Value> 
    </Setter> 
    <Setter Property="Template" > 
        <Setter.Value> 
            <ControlTemplate TargetType="telerik:SeriesItemLabel"> 
                <Canvas x:Name="PART_MainContainer"> 
                    <Path                             
                  Visibility="{TemplateBinding ConnectorVisibility}" 
                  Style="{TemplateBinding ConnectorStyle}" 
                  Stroke="{TemplateBinding Stroke}" 
                  StrokeThickness="{TemplateBinding StrokeThickness}"> 
                        <Path.Data> 
                            <PathGeometry > 
                                <PathGeometry.Figures> 
                                    <PathFigure x:Name="PART_Connector"> 
                                        <PathFigure.Segments> 
                                            <PolyLineSegment /> 
                                        </PathFigure.Segments> 
                                    </PathFigure> 
                                </PathGeometry.Figures> 
                            </PathGeometry> 
                        </Path.Data> 
                    </Path> 
                    <Border x:Name="PART_TextContainer" 
                   Style="{TemplateBinding LabelStyle}" 
                   BorderBrush="{TemplateBinding Stroke}" 
                   Background="Transparent" 
                   Width="{TemplateBinding Width}" 
                   Height="{TemplateBinding Height}"> 
                        <ContentPresenter Margin="{TemplateBinding Padding}" /> 
                    </Border> 
                </Canvas> 
            </ControlTemplate> 
        </Setter.Value> 
    </Setter> 
</Style> 

Don't forget to apply the Style to the SeriesItemLabelStyle property of the Series Definition:

radChart.DefaultSeriesDefinition.SeriesItemLabelStyle = this.Resources["MySeriesItemLabel_Style"] as Style; 
radChart.DefaultSeriesDefinition.SeriesItemLabelStyle = TryCast(Me.Resources("MySeriesItemLabel_Style"), Style) 

The result:

See Also

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