asp.net mvc 3 - Update and Create New Records in the Same Table -

how can apply changes first record in table , add 1 or more additional records same table? getting following exception:

an object same key exists in objectstatemanager. objectstatemanager cannot track multiple objects same key

see sample code below.

var student = db.student.where(d => d.studentid == studentid);                                         int count = 0;                                             if(student != null)                                             {                                                 foreach(var student in student)                                                 {                                                     if (student.id == id)                                                     {                                                         foreach (var assign in assignment)                                                         {                                                             if (assign != null && count == 0)                                                             {                                                                //how can save changes made first record here                                                                 assign.assignmentid = student.assignmentid;                                                                 db.assignment.applycurrentvalues(assign);                                                             }                                                              if (assign != null && count > 0)                                                             {                                                                 //how can add new records here                                                                 assign.assignmentid = student.assignmentid;                                                                 db.assignment.addobject(assign);                                                             }                                                             count++;                                                         }                                                     }                                                   }                                             } 

try calling save after line i.e.

db.assignment.applycurrentvalues(assign); db.savechanges(); 

then new entries:

var assignment = new assignement() { assignmentid = student.assignmentid }; db.assignments.add(model); db.savechanges();