Pie charts, the most common tools used for data visualization, are circular graphs that display the proportionate contribution of each category which is represented by a pie or a slice. The magnitude of the dependent variable is proportional to the angle of the slice. These charts can be used for plotting just one series with non-zero and positive values. For example, you can use a pie chart to show the market share of various automobile companies.

Create a WinForms Pie Chart

FlexChart for WinForms provides pie chart through a stand alone control which is represented by the FlexPie class. You can bind the chart with data using the FlexPie.DataSource property provided by the FlexPie class. This class also provides FlexPie.Binding and FlexPie.BindingName properties for setting numeric values and labels of the pie chart slices. You can also specify the angle from where you want to start drawing the slices in the clock wise direction by setting the StartAngle property. FlexChart also lets you create following variations of pie chart:

• Doughnut Chart: Set the InnerRadius property to a value greater than zero to create a hole in the center. By default, this property is set to zero.
• Exploded Pie Chart: Set the Offset property to a value greater than zero to push the slices away from the center. By default, this property is set to zero.
• Reversed Pie Chart: Set the Reversed property to true that creates the chart with angles drawn in the counter clockwise direction. By default, this property is set to false.

Doughnut Chart	Exploded Pie Chart	Reversed Pie Chart

To create a pie chart using FlexChart:

At design-time

1. Drag and drop the FlexPie control to the form.
2. Right click the FlexPie control on form to open the Properties window.
3. Set the data source using the DataSource property.
4. Set the Binding and BindingName property.

Using code

To create a WinForms pie chart through code, the first step after initializing the FlexPie control is to clear the default series and add a new series using the Add method. Set up the data source through the DataSource property and set the BindingName and Binding property. You can also set up the chart further by setting the other required properties such as header content, data label content etc.

//Binding FlexPie's AxisX to 'Value' so values appear in Horizontal axis
flexPie1.Binding = "Value";

flexPie1.BindingName = "Name";

//Specify what and how to show data values
flexPie1.DataLabel.Content = "{name} : {p:0}%";

//Specify where to position the data labels relative to pie slices
flexPie1.DataLabel.Position = PieLabelPosition.Radial;

//Setting FlexPie's Header
flexPie1.Header.Content = "Market Share of Automobile Companies";

//Passing data in FlexPie
flexPie1.DataSource = GetCarSales();

        ''' <summary>
        ''' Method for initializing FlexPie
        ''' </summary
        Protected Sub SetupChart()
#Region "SetupChart"
            'Binding FlexPie's AxisX to 'Value' so values appear in Horizontal axis
            flexPie1.Binding = "Value"

            flexPie1.BindingName = "Name"

            'Specify what and how to show data values
            flexPie1.DataLabel.Content = "{name} : {p:0}%"

            'Specify where to position the data labels relative to pie slices
            flexPie1.DataLabel.Position = PieLabelPosition.Radial

            'Setting FlexPie's Header
            flexPie1.Header.Content = "Market Share of Automobile Companies"

            'Passing data in FlexPie
            flexPie1.DataSource = GetCarSales()

Note that the above sample code uses a custom method named GetCarSales to supply data. You can set up the data source as per your requirements.

/// <summary>
/// Method for creating data for FlexPie
/// </summary>
public static List<CategoricalPoint> GetCarSales()
{
    var data = new List<CategoricalPoint>()
    {
        new CategoricalPoint{Name="Maruti", Value=1643467},
        new CategoricalPoint{Name="Hyundai", Value=536241},
        new CategoricalPoint{Name="Mahindra", Value=248859},
        new CategoricalPoint{Name="Tata", Value=210200},
        new CategoricalPoint{Name="Honda", Value=170026},
        new CategoricalPoint{Name="Toyota", Value=140645},
        new CategoricalPoint{Name="Renault", Value=102222},
        new CategoricalPoint{Name="Ford", Value=90061},
    };
    return data;
}

''' <summary>
''' Method for creating data for FlexPie
''' </summary>
Public Shared Function GetCarSales() As List(Of CategoricalPoint)
    Dim data As List(Of CategoricalPoint) = New List(Of CategoricalPoint)() From {
        New CategoricalPoint() With {
             .Name = "Maruti",
             .Value = 1643467
        },
        New CategoricalPoint() With {
             .Name = "Hyundai",
             .Value = 536241
        },
        New CategoricalPoint() With {
             .Name = "Mahindra",
             .Value = 248859
        },
        New CategoricalPoint() With {
             .Name = "Tata",
             .Value = 210200
        },
        New CategoricalPoint() With {
             .Name = "Honda",
             .Value = 170026
        },
        New CategoricalPoint() With {
             .Name = "Toyota",
             .Value = 140645
        },
        New CategoricalPoint() With {
             .Name = "Renault",
             .Value = 102222
        },
        New CategoricalPoint() With {
             .Name = "Ford",
             .Value = 90061
        }
    }
    Return data
End Function

Create Multiple Pie Charts

While a single pie chart is used to present the part-to-whole relationship in a group, the multiple pies are required for presenting or comparing data across various groups. For example, you can use multiple pies to compare quarterly sales figures of various car brands. With FlexChart, you can achieve this by simply setting the comma-separated field names from a data source in Binding property of the FlexPie class.

//Bind the FlexPie control with datasource
flexPie1.DataSource = data;
flexPie1.BindingName = "Name";
            
//Specify comma separated field names to render multiple pie charts
flexPie1.Binding = "Q1,Q2,Q3,Q4";
            
//Set titles of pie charts
flexPie1.Titles = new []{ "Quarter1", "Quarter2", "Quarter3", "Quarter4"};

//Set and position data labels for pie charts
flexPie1.DataLabel.Content = "{name}";
flexPie1.DataLabel.Position = C1.Chart.PieLabelPosition.Radial;

'Bind the FlexPie control with datasource
flexPie1.DataSource = data
flexPie1.BindingName = "Name"

'Specify comma separated field names to render multiple pie charts
flexPie1.Binding = "Q1,Q2,Q3,Q4"

'Set titles of pie charts
flexPie1.Titles = New String() {"Quarter1", "Quarter2", "Quarter3", "Quarter4"}

'Set and position data labels for pie charts
flexPie1.DataLabel.Content = "{name}"
flexPie1.DataLabel.Position = C1.Chart.PieLabelPosition.Radial