Visual Studio 2010 with .NET 4.0 not recognising System.Web.UI.DataVisualization.Charting

Question

I am using Visual Studio 2010 with .NET 4.0.

I have just started using the MS charting. When I complie the project, I get following error:

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

And also, in my code, this line has a squigly line underneath it indicating that the namespace cannot be found:

using System.Web.UI.DataVisualization.Charting;

However, if I go to my localhost to the page that has the chart in it, it renders fine.

The other strange thing is that when I compile (CTRL + SHIFT + B), I will get 3 compilation errors the first time I compile, then when I do it again, straight after, I get 16.

Even though I get the compilation errors above, I can still run the application and everything works fine, but it is really annoying that it won't compile so I must be doing something wrong.

Any help with this would be much appreciated.

Thanks.

Answer 1

Ok, figured out the problem.

I looked on Google ... StackOverflow and found this page, but I knew that the problem was not needing to be fixed by starting over.

I have ALL the references and fixed up web.config, and I still got the error.

Answer is to change the .Designer code from

protected global::System.Web.UI.WebControls.Chart chartDailyVolume;

to

protected global::System.Web.UI.DataVisualization.Charting.Chart chartDailyVolume;

I had copied and pasted code from another visual studio 2010 project to the page and the designer actually bound it wrong. When I dragged another Chart to the page and then removed it and compiled fine, I compared my checked in code from TFS to the new fix. Thus I noticed that the Designer.cs actually generated it wrong from a copy and paste even though both were visual studio 2010 solution projects (both with Target Framework of .NET Framework 4)

Answer 2

Click on Add References in your project and in the .NET Components tab add the System.Web.DataVisualization. This should solve your problem.