无法使用实体框架6更新实体

Question

I am trying to update an entity using following code.

 MemberFee originalMemberFee = db.MemberFees.FirstOrDefault(ann => ann.MemberId == memberFeeViewModel.MemberId && ann.Year == memberFeeViewModel.Year);

  if (originalMemberFee == null)
  {
        db.MemberFees.Add(memberFeeViewModel);
  }
  else
  {
       db.MemberFees.Attach(memberFeeViewModel);
       db.Entry(memberFeeViewModel).State = System.Data.Entity.EntityState.Modified;
  }
  db.SaveChanges();

It creates the entity (inside the if-sats) successfuly however it genereates this error when it tries to update an entity Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. Refresh ObjectStateManager entries. Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. Refresh ObjectStateManager entries.

Answer 1

It's possible that the memberFeeViewModel key(s) is not properly set.

Check your MemberId and Year value of memberFeeViewModel object. If those are empty then you need to provide the keys before updating.