in both Telerik.Charting.dll and RadChart.Net2.dll
RadChart has been replaced by RadHtmlChart, Telerik's client-side charting component. If you are considering RadChart for new development, examine the RadHtmlChart documentation and online demos first to see if it will fit your development needs. If you are already using RadChart in your projects, you can migrate to RadHtmlChart by following these articles: Migrating Series, Migrating Axes, Migrating Date Axes, Migrating Databinding, Features parity. Support for RadChart is discontinued as of Q3 2014, but the control will remain in the assembly so it can still be used. We encourage you to use RadHtmlChart for new development.
When upgrading existing Telerik UI applications (which include RadChart) to Telerik® UI for ASP.NET AJAX you may get the following error:
Error 1 The type 'Telerik.Charting.<SomeType> exists in both 'c:\WINDOWS\assembly\GAC_MSIL\Telerik.Charting\...\Telerik.Charting.dll' and 'c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\...\RadChart.Net2.DLL'
The reason for this error is because RadChart (3.x and later) and Telerik® UI for ASP.NET AJAX Chart use shared code.he shared code is in the form of Telerik.Charting.dll assembly which is ILMerged in the RadChart.Net2.dll for backwards compatibility reasons and is shipped separately for Telerik® UI for ASP.NET AJAX.
The error will manifest itself whenever you attempt to reference BOTH RadChart.Net2.dll and Telerik.Charting.dll. There are two ways to resolve the issue:
If you are migrating your projects to use Telerik® UI for ASP.NET AJAX you may initially want to remove the reference to the Telerik.Charting.dll from your Web.config file. In this case you will be using the old ASP.NET Chart and will not need the Telerik.Charting.dll that comes with the suite. The Telerik.Charting.dll is NOT required for the operation of the for ASP.NET AJAX controls other than Chart.
If you are already using RadChart for ASP.NET AJAX then you will need to remove the reference to RadChart.Net2.dll and continue using Telerik.Charting.dll
Please have in mind that RadChart for ASP.NET AJAX and RadChart 4.x have 99% identical functionality. It is up to your personal preference to decide which one you would like to use. The most significant difference is the assembly name and the fact that RadChart for ASP.NET AJAX uses an HttpHandler to display images and RadChart 4.x still uses RadControls\Image.aspx for backwards compatibility reasons.