Data Binding

TreeMap chart control binds to hierarchical data, to represent the elements of tree-like data as nested rectangles. Once the control binds to the data source and displays data items as rectangles, the size and color of these constituting rectangles enable analysis and comparison of data items.

TreeMap class exposes DataSource property, which takes collection of the objects, that contain data, to populate in tree map chart. The Binding and BindingName properties are instrumental in generating rectangular nodes for data items and their respective categories or groups. While Binding property takes string value depicting the name of the property of data item that contains numeric data value, helpful in calculating the size of rectangular nodes, BindingName takes string value depicting the name of data items. ChildItemPath property ensures that a hierarchical structure of the provided data collection is maintained, by communicating to the control about the child items within the data.

To elaborate how data is populated in a tree map chart, let’s consider a use case where we try to compare yearly sales (in units sold) of a multi-brand retail store. The analysis can then further be drilled down to quarters in a year and then to months in a quarter, by using Treemap chart. Here yearly sales are represented by the top level rectangles, quarterly sales in those years represent the subsequent level, and monthly sales form the next level that is leaf nodes in tree map.

The following image illustrates sales in a retail store, in terms of units sold, through TreeMap chart control. Note that the image shows hierarchical data up to third level, that is months in respective quarters of the years.

In this example, data generated in DataSource.cs class is serving as the source for tree map chart. DataSource property takes the hierarchical data collection generated in DataSource.cs class.

Create a hierarchical data source

In the code view, create a DataService.cs class to generate hierarchical data, as shown in the following code.

Visual Basic
C#

Visual Basic

Public Class DataService
    Private rnd As New Random()
    Shared _default As DataService

    Public Shared ReadOnly Property Instance() As DataService
        Get
            If _default Is Nothing Then
                _default = New DataService()
            End If

            Return _default
        End Get
    End Property

    Public Shared Function CreateHierarchicalData() As List(Of DataItem)
        Dim rnd As Random = Instance.rnd

        Dim years As New List(Of String)()
        Dim times As New List(Of List(Of String))() From {
            New List(Of String)() From {
                "Jan",
                "Feb",
                "Mar"
            },
            New List(Of String)() From {
                "Apr",
                "May",
                "June"
            },
            New List(Of String)() From {
                "Jul",
                "Aug",
                "Sep"
            },
            New List(Of String)() From {
                "Oct",
                "Nov",
                "Dec"
            }
        }

        Dim items As New List(Of DataItem)()
        Dim yearLen = Math.Max(CInt(Math.Round(Math.Abs(5 - Instance.rnd.NextDouble() * 10))), 3)
        Dim currentYear As Integer = DateTime.Now.Year
        For i As Integer = yearLen To 1 Step -1
            years.Add((currentYear - i).ToString())
        Next
        Dim quarterAdded = False

        years.ForEach(Function(y)
                          Dim i = years.IndexOf(y)
                          Dim addQuarter = Instance.rnd.NextDouble() > 0.5
                          If Not quarterAdded AndAlso i = years.Count - 1 Then
                              addQuarter = True
                          End If
                          Dim year = New DataItem() With {
                              .Year = y
                          }
                          If addQuarter Then
                              quarterAdded = True
                              times.ForEach(Function(q)
                                                Dim addMonth = Instance.rnd.NextDouble() > 0.5
                                                Dim idx As Integer = times.IndexOf(q)
                                                Dim quar As String
                                                quar = "Q" + (idx + 1).ToString
                                                Dim quarters = New DataItem() With {
                                                    .Year = y,
                                                    .Quarter = quar
                                                }
                                                If addMonth Then
                                                    q.ForEach(Function(m)
                                                                  quarters.Items.Add(New DataItem() With {
                                                                      .Year = y,
                                                                      .Quarter = quar,
                                                                      .Month = m,
                                                                      .Value = rnd.[Next](20, 30)
                                                                  })

                                                              End Function)
                                                Else
                                                    quarters.Value = rnd.[Next](80, 100)
                                                End If
                                                year.Items.Add(quarters)

                                            End Function)
                          Else
                              year.Value = rnd.[Next](80, 100)
                          End If
                          items.Add(year)

                      End Function)

        Return items
    End Function

End Class

public class DataService
{
    Random rnd = new Random();
    static DataService _default;

    public static DataService Instance
    {
        get
        {
            if (_default == null)
            {
                _default = new DataService();
            }

            return _default;
        }
    }

    public static List<DataItem> CreateHierarchicalData()
    {
        Random rnd = Instance.rnd;

        List<string> years = new List<string>();
        List<List<string>> times = new List<List<string>>()
        {
            new List<string>() { "Jan", "Feb", "Mar"},
            new List<string>() { "Apr", "May", "June"},
            new List<string>() { "Jul", "Aug", "Sep"},
            new List<string>() { "Oct", "Nov", "Dec" }
        };

        List<DataItem> items = new List<DataItem>();
        var yearLen = Math.Max((int)Math.Round(Math.Abs(5 - Instance.rnd.NextDouble() * 10)), 3);
        int currentYear = DateTime.Now.Year;
        for (int i = yearLen; i > 0; i--)
        {
            years.Add((currentYear - i).ToString());
        }
        var quarterAdded = false;

        years.ForEach(y =>
        {
            var i = years.IndexOf(y);
            var addQuarter = Instance.rnd.NextDouble() > 0.5;
            if (!quarterAdded && i == years.Count - 1)
            {
                addQuarter = true;
            }
            var year = new DataItem() { Year = y };
            if (addQuarter)
            {
                quarterAdded = true;
                times.ForEach(q =>
                {
                    var addMonth = Instance.rnd.NextDouble() > 0.5;
                    int idx = times.IndexOf(q);
                    var quar = "Q" + (idx + 1);
                    var quarters = new DataItem() { Year = y, Quarter = quar };
                    if (addMonth)
                    {
                        q.ForEach(m =>
                        {
                            quarters.Items.Add(new DataItem()
                            {
                                Year = y,
                                Quarter = quar,
                                Month = m,
                                Value = rnd.Next(20, 30)
                            });
                        });
                    }
                    else
                    {
                        quarters.Value = rnd.Next(80, 100);
                    }
                    year.Items.Add(quarters);
                });
            }
            else
            {
                year.Value = rnd.Next(80, 100);
            }
            items.Add(year);
        });

        return items;
    }

}

Create a DataItem class to define list of objects to represent data items and their categories.

Visual Basic
C#

Visual Basic

Public Class DataItem
    Private _items As List(Of DataItem)

    Public Property Year() As String
        Get
            Return m_Year
        End Get
        Set
            m_Year = Value
        End Set
    End Property
    Private m_Year As String
    Public Property Quarter() As String
        Get
            Return m_Quarter
        End Get
        Set
            m_Quarter = Value
        End Set
    End Property
    Private m_Quarter As String
    Public Property Month() As String
        Get
            Return m_Month
        End Get
        Set
            m_Month = Value
        End Set
    End Property
    Private m_Month As String
    Public Property Value() As Double
        Get
            Return m_Value
        End Get
        Set
            m_Value = Value
        End Set
    End Property
    Private m_Value As Double
    Public ReadOnly Property Items() As List(Of DataItem)
        Get
            If _items Is Nothing Then
                _items = New List(Of DataItem)()
            End If

            Return _items
        End Get
    End Property
End Class

public class DataItem
{
    List<DataItem> _items;

    public string Year { get; set; }
    public string Quarter { get; set; }
    public string Month { get; set; }
    public double Value { get; set; }
    public List<DataItem> Items
    {
        get
        {
            if (_items == null)
            {
                _items = new List<DataItem>();
            }

            return _items;
        }
    }
}

Bind TreeMap to the data source

Define a method named SetupChart() as shown in the following code snippet, to set appropriate properties for displaying the tree map chart.

Visual Basic
C#

Visual Basic

Private Sub SetupChart()
    TreeMap1.BeginUpdate()
    TreeMap1.DataSource = DataService.CreateHierarchicalData()
    TreeMap1.Binding = "Value"
    TreeMap1.BindingName = "Year,Quarter,Month"
    TreeMap1.ChildItemsPath = "Items"
    TreeMap1.MaxDepth = 3
    TreeMap1.ToolTip.Content = "{name}: {value} units"
    TreeMap1.ToolTip.IsBalloon = True
    TreeMap1.EndUpdate()
End Sub

void SetupChart()
{
    treeMap1.BeginUpdate();
    treeMap1.DataSource = DataService.CreateHierarchicalData();
    treeMap1.Binding = "Value";
    treeMap1.BindingName = "Year,Quarter,Month";
    treeMap1.ChildItemsPath = "Items";
    treeMap1.MaxDepth = 3;
    treeMap1.ToolTip.Content = "{name}: {value} units";            
    treeMap1.ToolTip.IsBalloon = true;     
    treeMap1.EndUpdate();
}

Call the SetupChart() method in the Form class constructor below the InitializeComponent() method.

Build and run the project
1. Click Build | Build Solution to build the project.
2. Press F5 to run the project.
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