MVC C# .NET - Fix Error - The type or namespace name 'DataVisualization' does not exist in the namespace 'System.Web.UI' (are you missing an assembly reference?)

Error    CS0234    The type or namespace name 'DataVisualization' does not exist in the namespace 'System.Web.UI' (are you missing an assembly reference?)   

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when trying to use
using System.Web.UI.DataVisualization.Charting;