C#

Scott Dorman wrote:

However, when the GC does collect an object it will call the Dispose method

viru04 wrote:

give value to the answers submitted by the user

viru04 wrote:

take the average of it

il_masacratore wrote:

Thats my point of view. There're persons who prefer work with collections because they think that more easy to maintain...

public interface IValid
{
  bool IsValid { get ; }
}

public void ItemBase
{
   /// <summary>
   /// Ensure that the string cannot be longer than a certain length.
   /// A simplistic approach to preventing buffer overruns.
   /// </summary>
   protected virtual string TrimString(string value, maxLength)
   {
     if (value == null || value.Trim().Length == 0)
       return value;
     value = value.Trim();
     if (value.Length > maxLength)
     {
       value = value.Substring(0, maxLength)
     }
     return value;
   }
}

public void Customer : ItemBase, IValid
{
  private string _forename;
  private string _surname;

  public Customer(string forename, string surname)
  {
    _forename = TrimString(forename, 30);
    _surname = TrimString(surname, 30);
  }

  /// <summary>
  /// Get or set the forename.
  /// </summary>
  public string Forename
  {
    get { return _forename; }
    set { _forename = TrimString(value, 30); }
  }

  /// <summary>
  /// Get or set the surname.
  /// </summary>
  public string Surname
  {
    get { return _surname; }
    set { _surname = TrimString(value, 30); }
  }

  /// <summary>
  /// A <see cref="Customer"/> must have a forename before being saved.
  /// </summary>
  public bool IsValid
  {
    get
    {
      bool valid = false;
      if (_forename != null && _forename.Trim().Length > 0)
        valid = true;
      return valid;
    }
  }
}

public abstract class BaseCollection<T> where T : IValid
{
  private List<T> _list;

  /// <summary>
  /// A collection of objects of type <T>.
  /// </summary>
  public List<T> Collection
  {
    get { return _list ; }
    set { _list = value; }
  }

  /// <summary>
  /// Add object T to the collection if valid.
  /// </summary>
  public void Add(T value)
  {
    if (value.IsValid)
    {
      _list.Add(T);
    }
    else
    {
      // This exception would normally be much more explicit.
      // This is not a good example of an exception message, but
      // constraints in posting width kind of necessitate this.
      throw new Exception("Invalid object.");
    }
  }
  /// <summary>
  /// Fill the collection from the datastore.
  /// </summary>
  public abstract void Fill();

  /// <summary>
  /// This method must be implemented to physically add the item to the
  /// collection. The values will be read out of the datareader and then
  /// added to the collection.
  /// </summary>
  protected abstract void AddRow(IDataReader dr);

  /// <summary>
  /// This method should be called from the <see cref="Fill" /> method
  /// to ensure that the collection is filled.
  /// </summary>
  protected void Add(IDataReader dr)
  {
    if (dr.HasRows)
    {
      while (dr.Read())
      {
        AddRow(dr);
      }
    }
  }

}

public class Customers : BaseCollection<Customer>
{
  /// <summary>
  /// Method to add fill the Customers collection.
  /// </summary>
  public override void Fill()
  {
    // Call the database and get a DataReader to fill the base
    // collection.
    using (SqlConnection conn = new SqlConnection(Utilities.ConnectionString))
    {
      using (SqlCommand cmd = new SqlCommand())
      {
        cmd.Connection = conn;
        cmd.CommandText = "GetAllCustomers";
        cmd.CommandType = CommandType.StoredProcedure;
        conn.Open();
        using (SqlDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection))
        {
           Add(dr);
        }
      }
    }
  }

  /// <summary>
  /// Add the customer information from the datareader into the collection.
  /// </summary>
  protected override void AddRow(IDataReader dr)
  {
    string forename = dr.GetString(dr.GetOrdinal("forename"));
    string surname = dr.GetString(dr.GetOrdinal("surname"));

    try
    {
      Add(new Customer(forename, surname));
    }
    catch (Exception ex)
    {
      Console.WriteLine(ex.Message);
    }
  }
}

customer.Surname = "Smith";

ds.Tables[0].Rows[0]["surname"] = "Smith";