IChildrenSelector.SelectChildren(Object) Method

Returns a child object collection from the specified object.

Namespace: DevExpress.Xpf.Charts

Assembly: DevExpress.Xpf.Charts.v24.2.dll

NuGet Package: DevExpress.Wpf.Charts

Declaration

C#

IEnumerable SelectChildren(
    object item
)

VB.NET

Function SelectChildren(
    item As Object
) As IEnumerable

Parameters

Name	Type	Description
item	Object	An object whose child collection is required.

Returns

Type	Description
IEnumerable	The child object collection. If the specified item does not have children the return value is null (or Nothing in Visual Basic).

Example

This example demonstrates how to enable the Chart’s Drill Mode that allows end users to navigate between different detail levels:

Data.cs

 public interface INameable {
    string Name { get; }
}

public sealed class DevAVBranch: INameable {
    public string Name { get; set; }
    public List<DevAVProductCategory> Categories { get; set; }
    public double TotalIncome { get => Categories.Sum(c => c.TotalIncome); }
}


public sealed class DevAVProductCategory: INameable {
    public string Name { get; set; }
    public List<DevAVProduct> Products { get; set; }
    public double TotalIncome { get => Products.Sum(p => p.TotalIncome); }
}


public sealed class DevAVProduct: INameable {
    public string Name { get; set; }
    public List<DevAVMonthlyIncome> Sales { get; set; }
    public double TotalIncome { get => Sales.Sum(s => s.Income); }
}


public class DevAVMonthlyIncome {
    public DateTime Month { get; set; }
    public double Income { get; set; }
}

Data.vb

Public Interface INameable
    ReadOnly Property Name As String
End Interface

Public Class DevAVBranch
    Implements INameable

    Public Property Name As String Implements INameable.Name
    Public Property Categories As List(Of DevAVProductCategory)
    Public ReadOnly Property TotalIncome As Double
        Get
            Return Categories.Sum(Function(c) c.TotalIncome)
        End Get
    End Property
End Class

Public Class DevAVProductCategory
    Implements INameable

    Public Property Name As String Implements INameable.Name
    Public Property Products As List(Of DevAVProduct)
    Public ReadOnly Property TotalIncome As Double
        Get
            Return Products.Sum(Function(p) p.TotalIncome)
        End Get
    End Property
End Class

Public Class DevAVProduct
    Implements INameable

    Public Property Name As String Implements INameable.Name
    Public Property Sales As List(Of DevAVMonthlyIncome)
    Public ReadOnly Property TotalIncome As Double
        Get
            Return Sales.Sum(Function(s) s.Income)
        End Get
    End Property
End Class

Public Class DevAVMonthlyIncome
    Public Property Month As DateTime
    Public Property Income As Double
End Class

MainViewModel.cs

class MainViewModel {
    public IReadOnlyList<DevAVBranch> Branches { get; } 

    public MainViewModel() {
        Branches = new BranchDAO().GetBranches();
    }
}

MainViewModel.vb

Class MainViewModel
    Private _branches As IReadOnlyList(Of DevAVBranch)
    Public ReadOnly Property Branches As IReadOnlyList(Of DevAVBranch)
        Get
            Return _branches
        End Get
    End Property

    Public Sub New()
        _branches = new BranchDAO().GetBranches();
    End Sub
End Class

MainWindow.xaml

<Window.DataContext>
    <local:MainViewModel/>
</Window.DataContext>
<Window.Resources>
    <!-- Other resources are here. -->
    <local:DevAVSeriesTemplateSelector
        x:Key="seriesTemplateSelector"
        AllCategoriesTemplate="{StaticResource stackedBarTemplate}"
        BranchCategoriesTemplate="{StaticResource barTemplate}"
        CategoryProductsTemplate="{StaticResource stackedSplineAreaTemplate}"
        ProductTemplate="{StaticResource splineTemplate}">
    </local:DevAVSeriesTemplateSelector>
    <local:DevAVSeriesChildrenSelector x:Key="childrenSelector"/>
    <local:DevAVBreadcrumbTextProvider x:Key="textProvider"/>
<Window.Resources>
<dxc:ChartControl>
    <dxc:XYDiagram2D
        x:Name="diagram" 
        SeriesItemTemplateSelector="{StaticResource seriesTemplateSelector}" 
        DrillDownStateChanged="XYDiagram2D_DrillDownStateChanged">
        <dxc:XYDiagram.SeriesItemsSource>
            <dxc:HierarchicalDataAdapter 
                DataSource="{Binding Branches}"
                ChildrenSelector="{StaticResource childrenSelector}"
                BreadcrumbTextProvider="{StaticResource textProvider}"/>
        </dxc:XYDiagram.SeriesItemsSource>
    </dxc:XYDiagram2D>
<!-- Other Chart Settings.-->
</dxc:ChartControl>

MainWindow.xaml.cs

class MainWindow: Window {
    public MainWindow() {
        InitializeComponent()
    }
    private void OnDrillDownStateChanged(object sender, DrillDownStateChangedEventArgs e) {
        diagram.Rotated = e.BreadcrumbItems.Last().IsHome;
    }
}

private void OnDrillDownStateChanged(object sender, DrillDownStateChangedEventArgs e) {
    diagram.Rotated = e.BreadcrumbItems.Last().IsHome;
}

class DevAVSeriesChildrenSelector : IChildrenSelector {
    public IEnumerable SelectChildren(object item) {
        if (item as DevAVBranch branch) return new List<DevAVBranch> { branch };
        if (item as DevAVProductCategory category) return category.Products;
        if (item as DevAVProduct product) return new List<DevAVProduct> { product };
        return null;
    }
}

class DevAVSeriesTemplateSelector : DataTemplateSelector {
    public DataTemplate AllCategoriesTemplate { get; set; }
    public DataTemplate BranchCategoriesTemplate { get; set; }
    public DataTemplate CategoryProductsTemplate { get; set; }
    public DataTemplate ProductTemplate { get; set; }

    public override DataTemplate SelectTemplate(object item, DependencyObject container) {
        Diagram diagram = (Diagram)container;
        if (item is DevAVBranch && diagram.BreadcrumbItems.Count == 1)
            return AllCategoriesTemplate;
        if (item is DevAVBranch)
            return BranchCategoriesTemplate;
        if (item is DevAVProduct && diagram.BreadcrumbItems[diagram.BreadcrumbItems.Count - 1].SourceObject is DevAVProduct)
            return ProductTemplate;
        if (item is DevAVProduct) 
            return CategoryProductsTemplate;
        return null;
    }
}

class DevAVBreadcrumbTextProvider : IBreadcrumbTextProvider {
    public string GetText(object seriesSourceObj, object pointSourceObj) {
        StringBuilder sb = new StringBuilder("(");
        if (seriesSourceObj != null) sb.Append(GetName(seriesSourceObj));
        if (seriesSourceObj != null && pointSourceObj != null) sb.Append(", ");
        if (pointSourceObj != null) sb.Append(GetName(pointSourceObj));
        sb.Append(")");
        return sb.ToString();
    }

    private string GetName(object obj) {
        if (obj is INameable nameable) return nameable.Name;
        return String.Empty;
    }
}

MainWindow.xaml.vb

Public Class MainWindow
    Private Sub Diagram_DrillDownStateChanged(sender As Object, e As DrillDownStateChangedEventArgs)
        diagram.Rotated = e.BreadcrumbItems.Last().IsHome
    End Sub
End Class

Public Class DevAVSeriesChildrenSelector
    Implements IChildrenSelector

    Public Function SelectChildren(item As Object) As IEnumerable Implements IChildrenSelector.SelectChildren
        Dim branch = TryCast(item, DevAVBranch)
        If (branch IsNot Nothing) Then Return New List(Of DevAVBranch) From { branch }

        Dim category = TryCast(item, DevAVProductCategory)
        If (category IsNot Nothing) Then Return category.Products

        Dim product = TryCast(item, DevAVProduct)
        If (product IsNot Nothing) Then Return New List(Of DevAVProduct) From { product }

        Return Nothing
    End Function
End Class

Class DevAVSeriesTemplateSelector
    Inherits DataTemplateSelector

    Public Property AllCategoriesTemplate As DataTemplate
    Public Property BranchCategoriesTemplate As DataTemplate
    Public Property CategoryProductsTemplate As DataTemplate
    Public Property ProductTemplate As DataTemplate

    Public Overrides Function SelectTemplate(item As Object, container As DependencyObject) As DataTemplate
        Dim diagram = CType(container, Diagram)

        Dim branch = TryCast(item, DevAVBranch)
        If (branch IsNot Nothing) And (diagram.BreadcrumbItems.Count = 1) Then Return AllCategoriesTemplate
        If (branch IsNot Nothing) Then Return BranchCategoriesTemplate

        Dim product = TryCast(item, DevAVProduct)
        Dim lastLevelSourceProduct = TryCast(diagram.BreadcrumbItems(diagram.BreadcrumbItems.Count - 1).SourceObject, DevAVProduct)
        If (product IsNot Nothing) And (lastLevelSourceProduct IsNot Nothing) Then Return ProductTemplate
        If (product IsNot Nothing) Then Return CategoryProductsTemplate

        Return Nothing
    End Function
End Class

Public Class DevAVBreadcrumbTextProvider
    Implements IBreadcrumbTextProvider
    Public Function GetText(seriesSourceObj As Object, pointSourceObj As Object) As String Implements IBreadcrumbTextProvider.GetText
        Dim sb = New StringBuilder("(")
        If (seriesSourceObj IsNot Nothing) Then sb.Append(GetName(seriesSourceObj))
        If (seriesSourceObj IsNot Nothing And pointSourceObj IsNot Nothing) Then sb.Append(", ")
        If (pointSourceObj IsNot Nothing) Then sb.Append(GetName(pointSourceObj))
        sb.Append(")")
        Return sb.ToString()
    End Function

    Private Function GetName(obj As Object) As String
        Dim nameable = TryCast(obj, INameable)
        If (nameable IsNot Nothing) Then Return nameable.Name
        Return String.Empty
    End Function
End Class

The table below lists classes and properties the code above includes:

Symbol	Description
Diagram.SeriesItemsSource	Gets or sets the collection of objects used to generate series.
HierarchicalDataAdapter	The data adapter that uses data objects with aggregation and composition relationships as data sources for different detail levels when the Chart control is in the Drill Mode.
HierarchicalDataAdapterBase.DataSource	Gets or set the collection of data source objects for the Chart in the Drill Mode.
HierarchicalDataAdapter.ChildrenSelector	Gets or sets an object that returns a child object collection from a data object on whose representation the end user clicked.
IChildrenSelector	An interface of a children selector for the HierarchicalDataAdapter.
HierarchicalDataAdapterBase.BreadcrumbTextProvider	Gets or sets the object that provides text for breadcrumb items when the Chart is in the Drill Mode.
IBreadcrumbTextProvider	An interface of a text provider for the HierarchicalDataAdapter.
Diagram.SeriesItemTemplateSelector	Gets or sets the custom logic for selecting a data template that converts a model object to a series.
Diagram.DrillDownStateChanged	Occurs when end users navigate by detail levels when the Chart is is the Drill Mode.