ProcessEmptyPointsMode Enum

using DevExpress.XtraCharts;
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Windows.Forms;

namespace EmptyPointRepsentation {
    public partial class Form1 : Form {
        ChartControl chart { get { return chartControl1; } }
        public Form1() {
            InitializeComponent();

            chart.DataSource = WeatherDataProvider.Data;
            Series series = new Series("Wind", ViewType.Bar);
            series.SetDataMembers("Date", "Wind");
            chart.Series.Add(series);

            BarSeriesView view = (BarSeriesView)series.View;

            EmptyPointOptions emptyPointOptions = view.EmptyPointOptions;
            emptyPointOptions.ProcessPoints = ProcessEmptyPointsMode.Interpolate;
            emptyPointOptions.Color = Color.FromArgb(100, Color.DarkGray); 

        }
    }

    public static class WeatherDataProvider {
        static List<WeatherPoint> data;

        public static List<WeatherPoint> Data {
            get {
                if (data == null)
                    InitCollection();
                return data;
            }
        }
        static void InitCollection() {
            data = new List<WeatherPoint>();
            int lastYear = DateTime.Now.Year - 1;
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 10) });
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 11), Wind = 5 });
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 12), Wind = 5 });
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 13), Wind = 6 });
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 14), Wind = 3 });
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 15) });
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 16), Wind = 6 });
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 17), Wind = 5 });
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 18), Wind = 5 });
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 19), Wind = 4 });
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 20), Wind = 3 });
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 21), Wind = 7 });
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 22), Wind = 2 });
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 23) });
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 24) });
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 25), Wind = 4 });
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 26), Wind = 5 });
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 27), Wind = 4 });
            data.Add(new WeatherPoint() { Date = new DateTime(lastYear, 7, 28), Wind = 4 });
        }

        public class WeatherPoint {
            public DateTime Date { get; set; }
            public double? Wind { get; set; }
        }
    }
}

Imports DevExpress.XtraCharts
Imports System
Imports System.Collections.Generic
Imports System.Drawing
Imports System.Windows.Forms

Namespace EmptyPointRepsentation
    Public Partial Class Form1
        Inherits Form

        Private ReadOnly Property chart As ChartControl
            Get
                Return chartControl1
            End Get
        End Property

        Public Sub New()
            InitializeComponent()
            chart.DataSource = Data
            Dim series As Series = New Series("Wind", ViewType.Bar)
            series.SetDataMembers("Date", "Wind")
            chart.Series.Add(series)
            Dim view As BarSeriesView = CType(series.View, BarSeriesView)
            Dim emptyPointOptions As EmptyPointOptions = view.EmptyPointOptions
            emptyPointOptions.ProcessPoints = ProcessEmptyPointsMode.Interpolate
            emptyPointOptions.Color = Color.FromArgb(100, Color.DarkGray)
        End Sub
    End Class

    Public Module WeatherDataProvider
        Private dataField As List(Of WeatherPoint)

        Public ReadOnly Property Data As List(Of WeatherPoint)
            Get
                If dataField Is Nothing Then Call InitCollection()
                Return dataField
            End Get
        End Property

        Private Sub InitCollection()
            dataField = New List(Of WeatherPoint)()
            Dim lastYear As Integer = Date.Now.Year - 1
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 10)
            })
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 11),
                .Wind = 5
            })
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 12),
                .Wind = 5
            })
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 13),
                .Wind = 6
            })
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 14),
                .Wind = 3
            })
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 15)
            })
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 16),
                .Wind = 6
            })
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 17),
                .Wind = 5
            })
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 18),
                .Wind = 5
            })
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 19),
                .Wind = 4
            })
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 20),
                .Wind = 3
            })
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 21),
                .Wind = 7
            })
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 22),
                .Wind = 2
            })
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 23)
            })
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 24)
            })
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 25),
                .Wind = 4
            })
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 26),
                .Wind = 5
            })
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 27),
                .Wind = 4
            })
            Call dataField.Add(New WeatherPoint() With {
                .[Date] = New DateTime(lastYear, 7, 28),
                .Wind = 4
            })
        End Sub

        Public Class WeatherPoint
            Public Property [Date] As Date
            Public Property Wind As Double?
        End Class
    End Module
End Namespace