//// 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;
    }