Entity Framework CRUD operations on a datagrid

Question

I have a List<T> bound to a datagrid and am trying to figure out how to save all the changes to the database (using Entity Framework), not just one row at a time; OR, at least a better way to commit changes from the datagrid to the database. I am using the MVVM pattern. Here is what I have as far as saving one row:

    private static PROJECT_EXPENSEEntities _service;

    //The default constructor
    public ProjectExpenseItemsRepository()
    {
        if (_service == null)
        {
            _service = new PROJECT_EXPENSEEntities();
        }
    }

  public void AddProjectExpenseItems(int projectExpenseID)
        {
            project_expense_items p = new project_expense_items();
            if (entityList != null)
            {
                p.project_expense_id = projectExpenseID;
                p.item_number = entityList.ItemNumber;
                p.item_description = entityList.ItemDescription;
                p.item_unit_price = entityList.ItemUnitPrice;
                p.item_qty = entityList.ItemQty;
                p.supplier_name = entityList.SupplierName;
                p.create_date = System.DateTime.Today;
                _service.AddObject("project_expense_items", p);
                _service.SaveChanges();
            }
        }

However, I would prefer to send the changes to all rows in the datagrid at once:

    public void AddProjectExpenseItems(List<ProjectExpenseItemsBO> entityList, int projectExpenseID)
    {
        project_expense_items p = new project_expense_items();
        if (entityList != null)
        {
// not sure what goes here, do I need a loop for each item in the list?
// I have a feeling I am going in the wrong direction with this...

            _service.AddObject("project_expense_items", entityList);
            _service.SaveChanges();
        }
    }

I haven't found many good examples on the web. If someone could point me to an example I'd appreciate it.