System.Web.UI.DataVisualization.Charting missing error in .net 4.0?(轉貼)

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

 Click on Add References in your project and Browse to C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.0 and add the System.Web.DataVisualization dll file.

Before adding the dll remove the previous one and make sure that change the Target Frameweok to V4.0 in the project properties.

This will solve your problem.