FlexChartで箱ひげ図を描画するには、箱ひげ図の系列作成用のBoxWhiskerクラスを使用します。

まず、このクラスの新規インスタンスを作成して、箱ひげ図に固有の各種プロパティ(*)を設定し、FlexChartのSeriesに追加します。
    *QuartileCalculation、ShowOutliers、ShowInnerPoints、ShowMeanLineなど
次いで、同じX値に対して複数のY値データを設定すると、内部的に箱ひげ図の四分位数、中央値などが計算され、箱ひげ図が描画されます。

以下に、2つの系列を持つ箱ひげ図を作成する簡単な設定コードを記載します。



◎サンプルコード（VB）

Imports C1.Chart
Imports C1.Win.Chart

Public Class Form1
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        ' データの作成
        Dim dt = New DataTable()
        dt.Columns.AddRange(New DataColumn() {
             New DataColumn("X", GetType(Date)),
             New DataColumn("Y1", GetType(Double)),
             New DataColumn("Y2", GetType(Double))
        })
        Dim dates = New Date() {
            Date.Today, Date.Today.AddDays(1),
            Date.Today.AddDays(2),
            Date.Today.AddDays(3),
            Date.Today.AddDays(4)
        }
        dt.Rows.Add(dates(0), 1, 2)
        dt.Rows.Add(dates(0), 3, 4)
        dt.Rows.Add(dates(0), 5, 6)
        dt.Rows.Add(dates(1), 1, 5)
        dt.Rows.Add(dates(1), 3, 7)
        dt.Rows.Add(dates(1), 5, 9)
        dt.Rows.Add(dates(2), 1, 6)
        dt.Rows.Add(dates(2), 3, 8)
        dt.Rows.Add(dates(2), 5, 10)
        dt.Rows.Add(dates(3), 1, 5)
        dt.Rows.Add(dates(3), 3, 7)
        dt.Rows.Add(dates(3), 5, 9)
        dt.Rows.Add(dates(4), 1, 2)
        dt.Rows.Add(dates(4), 3, 4)
        dt.Rows.Add(dates(4), 5, 6)
        dt.AcceptChanges()

        ' 箱ひげ図の作成
        Dim boxWhisker1 = New BoxWhisker With {
            .Name = "Item1",
            .BindingX = "X",
            .Binding = "Y1",
            .QuartileCalculation = QuartileCalculation.InclusiveMedian,
            .ShowInnerPoints = True,
            .ShowOutliers = True,
            .ShowMeanLine = True,
            .ShowMeanMarks = True
        }

        Dim boxWhisker2 = New BoxWhisker With {
            .Name = "Item2",
            .BindingX = "X",
            .Binding = "Y2",
            .QuartileCalculation = QuartileCalculation.InclusiveMedian,
            .ShowInnerPoints = True,
            .ShowOutliers = True,
            .ShowMeanLine = True,
            .ShowMeanMarks = True
        }

        ' チャートの設定
        FlexChart1.DataSource = dt
        FlexChart1.Series.Clear()
        FlexChart1.Series.Add(boxWhisker1)
        FlexChart1.Series.Add(boxWhisker2)
        FlexChart1.Legend.Position = Position.Bottom

        ' 軸の設定
        FlexChart1.AxisX.Format = "MM/dd"
        FlexChart1.AxisY.Min = 0
        FlexChart1.AxisY.Max = 10
    End Sub
End Class

◎サンプルコード（C#）

using C1.Chart;
using C1.Win.Chart;

namespace _20230301a
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            // データの作成
            var dt = new DataTable();
            dt.Columns.AddRange(new DataColumn[]{
                new DataColumn("X", typeof(DateTime)),
                new DataColumn("Y1", typeof(Double)),
                new DataColumn("Y2", typeof(Double))
            });
            var dates = new DateTime[] {
                DateTime.Today, DateTime.Today.AddDays(1), 
                DateTime.Today.AddDays(2), 
                DateTime.Today.AddDays(3), 
                DateTime.Today.AddDays(4) 
            };
            dt.Rows.Add(dates[0], 1, 2);
            dt.Rows.Add(dates[0], 3, 4);
            dt.Rows.Add(dates[0], 5, 6);
            dt.Rows.Add(dates[1], 1, 5);
            dt.Rows.Add(dates[1], 3, 7);
            dt.Rows.Add(dates[1], 5, 9);
            dt.Rows.Add(dates[2], 1, 6);
            dt.Rows.Add(dates[2], 3, 8);
            dt.Rows.Add(dates[2], 5, 10);
            dt.Rows.Add(dates[3], 1, 5);
            dt.Rows.Add(dates[3], 3, 7);
            dt.Rows.Add(dates[3], 5, 9);
            dt.Rows.Add(dates[4], 1, 2);
            dt.Rows.Add(dates[4], 3, 4);
            dt.Rows.Add(dates[4], 5, 6);
            dt.AcceptChanges();

            // 箱ひげ図の作成
            var boxWhisker1 = new BoxWhisker {
                Name = "Item1",
                BindingX = "X",
                Binding = "Y1",
                QuartileCalculation = QuartileCalculation.InclusiveMedian,
                ShowInnerPoints = true,
                ShowOutliers = true,
                ShowMeanLine = true,
                ShowMeanMarks = true
            };

            var boxWhisker2 = new BoxWhisker {
                Name = "Item2",
                BindingX = "X",
                Binding = "Y2",
                QuartileCalculation = QuartileCalculation.InclusiveMedian,
                ShowInnerPoints = true,
                ShowOutliers = true,
                ShowMeanLine = true,
                ShowMeanMarks = true
            };

            // チャートの設定
            flexChart1.DataSource = dt;
            flexChart1.Series.Clear();
            flexChart1.Series.Add(boxWhisker1);
            flexChart1.Series.Add(boxWhisker2);
            flexChart1.Legend.Position = Position.Bottom;

            // 軸の設定
            flexChart1.AxisX.Format = "MM/dd";
            flexChart1.AxisY.Min = 0;
            flexChart1.AxisY.Max = 10;
        }
    }