Server Error in '/' Application.

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Line 206:                        {
Line 207:                            dataUser.DateLastLogin = DateTime.Now;
Line 208:                            db.SubmitChanges();
Line 209:                        }
Line 210:                    }

[ChangeConflictException: Row not found or changed.]
   System.Data.Linq.ChangeProcessor.SubmitChanges(ConflictMode failureMode) +1273
   System.Data.Linq.DataContext.SubmitChanges(ConflictMode failureMode) +396
   AdminManager.API.Model.User.GetUserByUsername(String username, Boolean refreshCache) in C:\home\site\repository\AdminManager.API\Model\User.cs:208
   AdminManager.API.Model.User.get_Current() in C:\home\site\repository\AdminManager.API\Model\User.cs:145
   AdminManager.API.Web.Mvc.ApiSecurity.IsAuthorized(HttpActionContext actionContext) in C:\home\site\repository\AdminManager.API\Web\Mvc\ApiSecurity.cs:57
   System.Web.Http.AuthorizeAttribute.OnAuthorization(HttpActionContext actionContext) +40
   System.Web.Http.Filters.AuthorizationFilterAttribute.OnAuthorizationAsync(HttpActionContext actionContext, CancellationToken cancellationToken) +27
   System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +102
   System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +64
   System.Web.Http.Filters.<ExecuteAuthorizationFilterAsyncCore>d__2.MoveNext() +169
   System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +102
   System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +64
   System.Web.Http.Controllers.<ExecuteAsync>d__0.MoveNext() +954
   System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +102
   System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +64
   System.Web.Http.Dispatcher.<SendAsync>d__1.MoveNext() +557