Problem with Web,Config in Framework

Configuration Error Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately. Parser Error Message: Could not load type 'System.Data.Entity.Design.AspNet.EntityDesignerBuildProvider'. Source Error: Line 129: <add extension=".exclude" type="System.Web.Compilation.IgnoreFileBuildProvider" /> Line 130: <add extension=".refresh" type="System.Web.Compilation.IgnoreFileBuildProvider" /> Line 131: <add extension=".edmx" type="System.Data.Entity.Design.AspNet.EntityDesignerBuildProvider" /> Line 132: <add extension=".xoml" type="System.ServiceModel.Activation.WorkflowServiceBuildProvider, System.WorkflowServices, Version=4.0.0.0, Cul ...