AspNetCompiler Error

When I'm trying to build ASP.NET using below configuration
Runner Type: Visual Studio (sln)
Solution File Path :  Studentplanner.sln
Visual Studio: Microsoft Visual Studio 2010
Targets: Rebuild
Configuration: Debug


When I'm trying to run this build I'm getting below error.

c:\TeamCityV3\buildAgent\work\9ebcc67e33ce912f\KS.Web\Master\SiteBaseV2.master(61, 0): error CS0433: The type 'UserControl_WebUserControl' exists in both 'c:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\ks.web\375b9c32\63b1117\App_Web_gqxonfdm.dll' and 'c:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\ks.web\375b9c32\63b1117\App_Web_tprmqst0.dll'

Could anyone suggest me how can I get rid of this error.

Thanks
Phaneendra