SwiftPointDrawOptions Class

using DevExpress.XtraCharts;

namespace SwiftPointChart {
    public partial class Form1 : Form {
        public Form1() {
            InitializeComponent();
            //...

            chartControl1.CustomDrawSeries += OnChartControlCustomDrawSeries;
        }

        private void OnChartControlCustomDrawSeries(object sender, CustomDrawSeriesEventArgs e) {
            SwiftPointDrawOptions drawOptions = (SwiftPointDrawOptions)e.SeriesDrawOptions;
            if (e.Series.Points.Count < 100) { drawOptions.Marker.Size = 20; }
        }
    }
}

Imports DevExpress.XtraCharts

Namespace SwiftPointChart
    Public Partial Class Form1
        Inherits Form

        Public Sub New()
            InitializeComponent()
            '...

            chartControl1.CustomDrawSeries += AddressOf OnChartControlCustomDrawSeries
        End Sub

        Private Sub OnChartControlCustomDrawSeries(ByVal sender As Object, ByVal e As CustomDrawSeriesEventArgs)
            Dim drawOptions As SwiftPointDrawOptions = CType(e.SeriesDrawOptions, SwiftPointDrawOptions)

            If e.Series.Points.Count < 100 Then
                drawOptions.Marker.Size = 20
            End If
        End Sub
    End Class
End Namespace