# Data Binding
## Content
The 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.
FlexChartBase class exposes ItemsSource 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 DataService class is serving as the source for tree map chart.
1. **Create a hierarchical data source**
1. In the code view, create a DataService class to generate hierarchical data, as shown in the following code.
**vbnet**
```vbnet
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
```
**csharp**
```csharp
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 CreateHierarchicalData()
{
Random rnd = Instance.rnd;
List years = new List();
List> times = new List>()
{
new List() { "Jan", "Feb", "Mar"},
new List() { "Apr", "May", "June"},
new List() { "Jul", "Aug", "Sep"},
new List() { "Oct", "Nov", "Dec" }
};
List items = new List();
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;
}
}
```
2. Create a DataItem class to define list of objects to represent data items and their categories.
**vbnet**
```vbnet
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
```
**csharp**
```csharp
public class DataItem
{
List _items;
public string Year { get; set; }
public string Quarter { get; set; }
public string Month { get; set; }
public double Value { get; set; }
public List Items
{
get
{
if (_items == null)
{
_items = new List();
}
return _items;
}
}
}
```
2. **Bind TreeMap to the data source**
To bind the TreeMap control to the data source use the following code.
```xml
```
**vbnet**
```vbnet
Public Class TreeMapViewModel
Public ReadOnly Property HierarchicalData() As List(Of DataItem)
Get
Return DataService.CreateHierarchicalData()
End Get
End Property
End Class
```
**csharp**
```csharp
public class TreeMapViewModel
{
public List HierarchicalData
{
get
{
return DataService.CreateHierarchicalData();
}
}
}
```
3. **Build and run the project**
1. Click **Build \| Build Solution** to build the project.
2. Press **F5** to run the project.
## See Also
[Quick Start](/componentone/docs/wpf/online-flexchart/TreeMapOverview/TreeMapQuickStart)
[Elements](/componentone/docs/wpf/online-flexchart/TreeMapOverview/TreeMapElements)