棒グラフに塗りつぶしパターンを適用するには、SeriesクラスのStyle.FillプロパティにHatchBrushを設定します。

（設定例）
例えば、左上から右下への対角線パターンを設定するには、HatchBrushの引数にHatchStyle.ForwardDiagonalを指定します。

series1.Style.Fill = New HatchBrush(HatchStyle.ForwardDiagonal, Color.Red, Color.White)

    ※上記コードでは、塗りつぶしの色として Color.Red も設定しています。

以下に、４つのシリーズに異なる塗りつぶしパターンを設定するサンプルを記載します。



◎サンプルコード（VB）

Imports System.Drawing.Drawing2D
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 As New DataTable()
        dt.Columns.AddRange({
                            New DataColumn("X", GetType(String)),
                            New DataColumn("Y1", GetType(Int32)),
                            New DataColumn("Y2", GetType(Int32)),
                            New DataColumn("Y3", GetType(Int32)),
                            New DataColumn("Y4", GetType(Int32))
        })
        For i = 0 To 5
            dt.Rows.Add($"{Chr(65 + i)}", i + 1, i + 2, i + 3, i + 4)
        Next
        dt.AcceptChanges()

        ' シリーズの作成
        Dim series1 As New Series() With {
            .Name = "S1",
            .Binding = "Y1",
            .BindingX = "X"
        }
        series1.Style.Fill = New HatchBrush(HatchStyle.ForwardDiagonal, Color.Red, Color.White)
        series1.Style.StrokeColor = Color.Black
        series1.Style.StrokeWidth = 1

        Dim series2 As New Series() With {
            .Name = "S2",
            .Binding = "Y2",
            .BindingX = "X"
        }
        series2.Style.Fill = New HatchBrush(HatchStyle.BackwardDiagonal, Color.Blue, Color.White)
        series2.Style.StrokeColor = Color.Black
        series2.Style.StrokeWidth = 1

        Dim series3 As New Series() With {
            .Name = "S3",
            .Binding = "Y3",
            .BindingX = "X"
        }
        series3.Style.Fill = New HatchBrush(HatchStyle.Cross, Color.LightSlateGray, Color.White)
        series3.Style.StrokeColor = Color.Black
        series3.Style.StrokeWidth = 1

        Dim series4 As New Series() With {
            .Name = "S4",
            .Binding = "Y4",
            .BindingX = "X"
        }
        series4.Style.Fill = New HatchBrush(HatchStyle.DarkHorizontal, Color.LightGreen, Color.White)
        series4.Style.StrokeColor = Color.Black
        series4.Style.StrokeWidth = 1

        ' 棒グラフの作成
        With FlexChart1
            .ChartType = ChartType.Column
            .DataSource = dt
            .Series.Clear()
            .Series.Add(series1)
            .Series.Add(series2)
            .Series.Add(series3)
            .Series.Add(series4)
        End With
    End Sub
End Class

◎サンプルコード（C#）

using System.Drawing.Drawing2D;
using C1.Chart;
using C1.Win.Chart;

namespace prj_C1FlexChart
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();

            // データの作成
            DataTable dt = new DataTable();
            dt.Columns.AddRange(new DataColumn[]
            {
                new DataColumn("X", typeof(String)),
                new DataColumn("Y1", typeof(Int32)),
                new DataColumn("Y2", typeof(Int32)),
                new DataColumn("Y3", typeof(Int32)),
                new DataColumn("Y4", typeof(Int32))
            });
            for (int i = 0; i <= 5; i++)
            {
                dt.Rows.Add(((char)(65 + i)).ToString(), i + 1, i + 2, i + 3, i + 4);
                dt.AcceptChanges();
            }

            // シリーズの作成
            Series series1 = new Series()
            {
                Name = "S1",
                Binding = "Y1",
                BindingX = "X"
            };
            series1.Style.Fill = new HatchBrush(HatchStyle.ForwardDiagonal, Color.Red, Color.White);
            series1.Style.StrokeColor = Color.Black;
            series1.Style.StrokeWidth = 1;

            Series series2 = new Series()
            {
                Name = "S2",
                Binding = "Y2",
                BindingX = "X"
            };
            series2.Style.Fill = new HatchBrush(HatchStyle.BackwardDiagonal, Color.Blue, Color.White);
            series2.Style.StrokeColor = Color.Black;
            series2.Style.StrokeWidth = 1;

            Series series3 = new Series()
            {
                Name = "S3",
                Binding = "Y3",
                BindingX = "X"
            };
            series3.Style.Fill = new HatchBrush(HatchStyle.Cross, Color.LightSlateGray, Color.White);
            series3.Style.StrokeColor = Color.Black;
            series3.Style.StrokeWidth = 1;

            Series series4 = new Series()
            {
                Name = "S4",
                Binding = "Y4",
                BindingX = "X"
            };
            series4.Style.Fill = new HatchBrush(HatchStyle.DarkHorizontal, Color.LightGreen, Color.White);
            series4.Style.StrokeColor = Color.Black;
            series4.Style.StrokeWidth = 1;

            // 棒グラフの作成
            flexChart1.ChartType = ChartType.Column;
            flexChart1.DataSource = dt;
            flexChart1.Series.Clear();
            flexChart1.Series.Add(series1);
            flexChart1.Series.Add(series2);
            flexChart1.Series.Add(series3);
            flexChart1.Series.Add(series4);
        }
    }
}