Converting 2008 application into 2010 asp.net

" Error10'FDR.Properties.Settings' does not contain a definition for 'RPCSS_DEVConnectionString' and no extension method 'RPCSS_DEVConnectionString' accepting a first argument of type 'FDR.Properties.Settings' could be found (are you missing a using directive or an assembly reference?)C:\RPCSS\_svn_code_working_on_5032013_second_copy\FDR\FdrApp\eRPT.designer.cs5860FDR App  "

        public eRPTDataContext()

            : base(global::FDR.Properties.Settings.Default.RPCSS_DEVConnectionString, mappingSource)

        {

            OnCreated();

        }