Pls help me to solve this error:
There is already an open DataReader associated with this Command which must be closed first.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.InvalidOperationException: There is already an open DataReader associated with this Command which must be closed first.
Source Error:
Line 46:                 string url = HttpContext.Current.Request.Url.Authority.ToLower();
Line 47:                 IEnumerable<Portal> portals = _inmemorycacheService.Get(PortalsHolder, () => _portalRepository.ListPortals());
Line 48:                 return portals.Where(portal => portal.URLAuthority.Equals(url)).FirstOrDefault();
Line 49:             }
Line 50: 
Source File: C:\Users\xxx\Desktop\MvcCms\MvcCms.Core\Cache\CacheService.cs    Line: 48