I see that this question has been asked a lot, however I haven't found anything yet that solves the problem I'm having. Obviously i'm using the Entity Framework to perform an update to a record. Once the updates are complete, however, whenever I try to save I get the following error message: An object with the same key already exists in the objectstatemanager At first I was passing in a collection object from the view that contained a copy of the the ZipCodeTerritory model object zipToUpdate. I changed the code by pulling this object out and just sending in the relevant fields instead. However, I'm still getting the same error. What's also weird is the first time I run this code, it works fine. Any attempt after that I get the error. Controller Here is the code from the method calling the edit function public static string DescriptionOnly(ZipCodeIndex updateZip) { if (!string.IsNullOrWhiteSpace(updateZip.newEffectiveDate) || !string.IsNullOrWhiteSpace(updateZip.newEndDate)) { return "Neither effective or end date can be present if updating Territory Code only; "; } _updated = 0; foreach (var zipCode in updateZip.displayForPaging.Where(x => x.Update)) { ProcessAllChanges(zipCode, updateZip.newTerritory, updateZip.newStateCode, updateZip.newDescription, updateZip.newChannelCode); } _msg += _updated + " record(s) updated; "; return _msg; } And here is the method that actually does the updating. private static void ProcessAllChanges(ZipCodeTerritory zipToUpdate, string newTerritory, string newStateCode, string newDescription, string newChannelCode) { try { if (!string.IsNullOrWhiteSpace(newTerritory)) zipToUpdate.IndDistrnId = newTerritory; if (!string.IsNullOrWhiteSpace(newStateCode)) zipToUpdate.StateCode = newStateCode; if (!string.IsNullOrWhiteSpace(newDescription)) zipToUpdate.DrmTerrDesc = newDescription; if (!string.IsNullOrWhiteSpace(newChannelCode)) zipToUpdate.ChannelCode = newChannelCode; if (zipToUpdate.EndDate == DateTime.MinValue) zipToUpdate.EndDate = DateTime.MaxValue; _db.Entry(zipToUpdate).State = EntityState.Modified; _db.SaveChanges(); _updated++; } catch (DbEntityValidationException dbEx) { _msg += "Error during update; "; EventLog.WriteEntry("Monet", "Error during ProcessAllChanges: " + zipToUpdate.ToString() + " |EX| " + dbEx.Message); } catch (Exception ex) { _msg += "Error during update; "; EventLog.WriteEntry("Monet", "Error during ProcessAllChanges: " + zipToUpdate.ToString() + " |MESSAGE| " + ex.Message); } } EDIT The ZipCodeIndex object contains a list of ZipCodeTerritory model objects. These aren't being pulled from a linq query, but instead simply passed back to the controller from the view. Here is the signature of the controller method that starts the process: [HttpPost] public ActionResult Update(ZipCodeIndex updateZip, string button)