How to: Add a Constant Line to an Axis

Dec 05, 2022
3 minutes to read

This example demonstrates how to create and customize a constant line at runtime.

Since constant lines belong to a diagram’s axis, you need to cast your diagram object to the appropriate diagram’s type. After that, you can access axes and manage their constant lines collection.

View Example

C#
VB.NET

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

namespace ConstLines {
    public partial class Form1 : Form {
        public Form1() {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e) {
            // Create an empty chart.
            ChartControl chartControl1 = new ChartControl();

            // Create a bar series and add points to it.
            Series series1 = new Series("Series 1", ViewType.Spline);
            series1.Points.Add(new SeriesPoint("A", new double[] { 10 }));
            series1.Points.Add(new SeriesPoint("B", new double[] { 2 }));
            series1.Points.Add(new SeriesPoint("C", new double[] { 17 }));
            series1.Points.Add(new SeriesPoint("D", new double[] { 4 }));
            series1.Points.Add(new SeriesPoint("E", new double[] { 17 }));
            series1.Points.Add(new SeriesPoint("F", new double[] { 10 }));
            series1.Points.Add(new SeriesPoint("G", new double[] { 15 }));

            // Add the series to the chart.
            chartControl1.Series.Add(series1);

            // Cast the chart's diagram to the XYDiagram type, to access its axes.
            XYDiagram diagram = chartControl1.Diagram as XYDiagram;

            // Create a constant line.
            ConstantLine constantLine1 = new ConstantLine("Constant Line 1");
            diagram.AxisY.ConstantLines.Add(constantLine1);

            // Define its axis value.
            constantLine1.AxisValue = 7;

            // Customize the behavior of the constant line.
            constantLine1.Visible = true;
            constantLine1.ShowInLegend = true;
            constantLine1.LegendText = "Some Threshold";
            constantLine1.ShowBehind = false;

            // Customize the constant line's title.
            constantLine1.Title.Visible = true;
            constantLine1.Title.Text = "Constant Line Title";
            constantLine1.Title.TextColor = Color.Red;
            constantLine1.Title.EnableAntialiasing = DevExpress.Utils.DefaultBoolean.False;
            constantLine1.Title.DXFont = new DXFont("Tahoma", 14, DXFontStyle.Bold);
            constantLine1.Title.ShowBelowLine = true;
            constantLine1.Title.Alignment = ConstantLineTitleAlignment.Far;

            // Customize the appearance of the constant line.
            constantLine1.Color = Color.Red;
            constantLine1.LineStyle.DashStyle = DashStyle.Dash;
            constantLine1.LineStyle.Thickness = 2;

            // Add the chart to the form.
            chartControl1.Dock = DockStyle.Fill;
            this.Controls.Add(chartControl1);
        }
    }
}

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

Namespace ConstLines

    Public Partial Class Form1
        Inherits Form

        Public Sub New()
            InitializeComponent()
        End Sub

        Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs)
            ' Create an empty chart.
            Dim chartControl1 As ChartControl = New ChartControl()
            ' Create a bar series and add points to it.
            Dim series1 As Series = New Series("Series 1", ViewType.Spline)
            series1.Points.Add(New SeriesPoint("A", New Double() {10}))
            series1.Points.Add(New SeriesPoint("B", New Double() {2}))
            series1.Points.Add(New SeriesPoint("C", New Double() {17}))
            series1.Points.Add(New SeriesPoint("D", New Double() {4}))
            series1.Points.Add(New SeriesPoint("E", New Double() {17}))
            series1.Points.Add(New SeriesPoint("F", New Double() {10}))
            series1.Points.Add(New SeriesPoint("G", New Double() {15}))
            ' Add the series to the chart.
            chartControl1.Series.Add(series1)
            ' Cast the chart's diagram to the XYDiagram type, to access its axes.
            Dim diagram As XYDiagram = TryCast(chartControl1.Diagram, XYDiagram)
            ' Create a constant line.
            Dim constantLine1 As ConstantLine = New ConstantLine("Constant Line 1")
            diagram.AxisY.ConstantLines.Add(constantLine1)
            ' Define its axis value.
            constantLine1.AxisValue = 7
            ' Customize the behavior of the constant line.
            constantLine1.Visible = True
            constantLine1.ShowInLegend = True
            constantLine1.LegendText = "Some Threshold"
            constantLine1.ShowBehind = False
            ' Customize the constant line's title.
            constantLine1.Title.Visible = True
            constantLine1.Title.Text = "Constant Line Title"
            constantLine1.Title.TextColor = Color.Red
            constantLine1.Title.EnableAntialiasing = DevExpress.Utils.DefaultBoolean.False
            constantLine1.Title.DXFont = New DXFont("Tahoma", 14, DXFontStyle.Bold)
            constantLine1.Title.ShowBelowLine = True
            constantLine1.Title.Alignment = ConstantLineTitleAlignment.Far
            ' Customize the appearance of the constant line.
            constantLine1.Color = Color.Red
            constantLine1.LineStyle.DashStyle = DashStyle.Dash
            constantLine1.LineStyle.Thickness = 2
            ' Add the chart to the form.
            chartControl1.Dock = DockStyle.Fill
            Me.Controls.Add(chartControl1)
        End Sub
    End Class
End Namespace