XtraCharts > 示例 > 如何： 创建自定义汇总函数

XtraCharts 提供了对系列值计算多个内置汇总函数的功能 (MIN、MAX、SUM、AVERAGE、COUNT)。 除了所提供的汇总函数之外，还可以创建自定义汇总，用于在应用程序中以任何所需的方式来计算汇总值。 此外，使用把自定义汇总函数注册到特定图表实例的实用方法，可以让最终用户在 图表向导 中使用自定义汇总函数。

下面的示例演示了如何创建一个自定义汇总函数，它返回两个值的乘积 (Price * Count)。 要完成此任务，需要创建一个汇总函数委托，并通过 ChartControl.RegisterSummaryFunction (或 WebChartControl.RegisterSummaryFunction) 方法注册它。

下面的代码说明了如何完成此任务。

C#CopyCode image复制代码
using System;
using System.Windows.Forms;
using DevExpress.XtraCharts;
// ...
 
namespace WindowsApplication1 {
    public partial class Form1 : Form {
 
        // Declare the Product summary function.
        private static SeriesPoint[] CalcProductValue(Series series, object argument, 
        string[] functionArguments, DataSourceValues[] values) {
 
            // Create an array of the resulting series points.
            SeriesPoint[] points = new SeriesPoint[values.Length];
 
            // Calculate the resulting series points as Price * Count.
            for (int i = 0; i < values.Length; i++)
                points[i] = new SeriesPoint(argument,
                    Convert.ToDouble(values[i][functionArguments[0]]) * 
                    Convert.ToDouble(values[i][functionArguments[1]]));
 
            // Return the result.
            return points;
        }
 
        public Form1() {
            InitializeComponent();
 
            // Create argument descriptions for the summary function.
            SummaryFunctionArgumentDescription argument1Description = 
                new SummaryFunctionArgumentDescription("Price", ScaleType.Numerical);
            SummaryFunctionArgumentDescription argument2Description = 
                new SummaryFunctionArgumentDescription("Count", ScaleType.Numerical);
 
            // Register the summary function in a chart.
            chartControl1.RegisterSummaryFunction("PRODUCT", "PRODUCT", 1, 
                new SummaryFunctionArgumentDescription[] { 
                    argument1Description, argument2Description },
                CalcProductValue);
 
            // Provide a datasource for the chart.
            chartControl1.DataSource = nwindDataSet.Products;
        }
 
        private void Form1_Load(object sender, EventArgs e) {
            // This line of code loads data into the 'nwindDataSet.Products' table.
            this.productsTableAdapter.Fill(this.nwindDataSet.Products);
 
        }
    }
}
Visual BasicCopyCode image复制代码
Imports System
Imports System.Windows.Forms
Imports DevExpress.XtraCharts
' ...
  
Public Class Form1
 
    ' Declare the Product summary function.
    Private Shared Function CalcProductValue(ByVal series As Series, _ 
    ByVal argument As Object, ByVal functionArguments() As String, _ 
    ByVal values() As DataSourceValues) As SeriesPoint()
 
        ' Create an array of the resulting series points.
        Dim points(values.Length - 1) As SeriesPoint
 
        ' Calculate the resulting series points as Price * Count.
        For i As Integer = 0 To values.Length - 1
            points(i) = New SeriesPoint(argument, _
            Convert.ToDouble(values(i)(functionArguments(0))) * _
            Convert.ToDouble(values(i)(functionArguments(1))))
        Next i
 
        ' Return the result.
        Return points
    End Function
 
    Public Sub New()
        InitializeComponent()
 
        ' Create argument descriptions for the summary function.
        Dim argument1Description As New SummaryFunctionArgumentDescription("Price", _ 
            ScaleType.Numerical)
        Dim argument2Description As New SummaryFunctionArgumentDescription("Count", _
            ScaleType.Numerical)
 
        ' Register the summary function in a chart.
        ChartControl1.RegisterSummaryFunction("PRODUCT", "PRODUCT", 1, _ 
            New SummaryFunctionArgumentDescription() {argument1Description, _ 
                argument2Description}, AddressOf CalcProductValue)
 
        ' Provide a datasource for the chart.
        ChartControl1.DataSource = ProductsBindingSource
    End Sub
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) _
    Handles MyBase.Load
        ' This line of code loads data into the 'NwindDataSet.Products' table.
        Me.ProductsTableAdapter.Fill(Me.NwindDataSet.Products)
    End Sub
 
End Class

CodeCentralShow Me

在 DevExpress Code Central 数据库中可以找到完整的示例项目，网址是 http://www.devexpress.com/example=E368。 取决于目标平台类型 (ASP.NET、WinForms 等)，可以在线运行本示例，或者下载自动可执行的示例。

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