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Gets or sets the object that provides a user-defined calculation of the TrendLine.
[Browsable(false)]
public ICustomTrendLine CustomTrendLine { get; set; }
To obtain complete control of the TrendLine calculations, a class inheriting from ICustomTrendLine can be implemented and instantiated. After the CustomTrendLine property is set to an instance of such an object, the chart will plot the user-defined TrendLine with the appropriate styles and legend entry.