请各位前辈看一下下面这段C#代码，update方法的参数怎么传递的

//// Update the Employee by ID.//   This method assumes that ConflictDetection is set to OverwriteValues.publicint UpdateEmployee(NorthwindEmployee employee)    {      if (String.IsNullOrEmpty(employee.FirstName))        thrownew ArgumentException("FirstName cannot be null or an empty string.");      if (String.IsNullOrEmpty(employee.LastName))        thrownew ArgumentException("LastName cannot be null or an empty string.");      if (employee.Address    == null) { employee.Address    = String.Empty; }      if (employee.City       == null) { employee.City       = String.Empty; }      if (employee.Region     == null) { employee.Region     = String.Empty; }      if (employee.PostalCode == null) { employee.PostalCode = String.Empty; }      SqlConnection conn = new SqlConnection(_connectionString);      SqlCommand    cmd  = new SqlCommand("UPDATE Employees " +                                           "  SET FirstName=@FirstName, LastName=@LastName, " +                                           "  Address=@Address, City=@City, Region=@Region, " +                                          "  PostalCode=@PostalCode " +                                          "  WHERE EmployeeID=@EmployeeID", conn);        cmd.Parameters.Add("@FirstName",  SqlDbType.VarChar, 10).Value = employee.FirstName;      cmd.Parameters.Add("@LastName",   SqlDbType.VarChar, 20).Value = employee.LastName;      cmd.Parameters.Add("@Address",    SqlDbType.VarChar, 60).Value = employee.Address;      cmd.Parameters.Add("@City",       SqlDbType.VarChar, 15).Value = employee.City;      cmd.Parameters.Add("@Region",     SqlDbType.VarChar, 15).Value = employee.Region;      cmd.Parameters.Add("@PostalCode", SqlDbType.VarChar, 10).Value = employee.PostalCode;      cmd.Parameters.Add("@EmployeeID", SqlDbType.Int).Value = employee.EmployeeID;      int result = 0;      try      {        conn.Open();        result = cmd.ExecuteNonQuery();      }      catch (SqlException e)      {        // Handle exception.      }      finally      {        conn.Close();      }      return result;    }