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[70-536] - CollectionBase class


Area di riferimento

- Developing applications that use system types and collections
    - Manage a group of associated data in a .NET Framework application by using collections. (Refer System.Collections namespace)
        - CollectionBase class


CollectionBase class

La classe astratta CollectionBase fornisce un punto di partenza per l'implementazione di collection fortemente tipizzate.
Ecco come è definita:

[Serializable, ComVisible(true)]
public abstract class CollectionBase : IList, ICollection, IEnumerable
{
    // Fields
    private ArrayList list;     // Utilizza un ArrayList internamente

    // Methods
    protected CollectionBase();
    protected CollectionBase(int capacity);
    public void Clear();
    public IEnumerator GetEnumerator();
    protected virtual void OnClear();
    protected virtual void OnClearComplete();
    protected virtual void OnInsert(int index, object value);
    protected virtual void OnInsertComplete(int index, object value);
    protected virtual void OnRemove(int index, object value);
    protected virtual void OnRemoveComplete(int index, object value);
    protected virtual void OnSet(int index, object oldValue, object newValue);
    protected virtual void OnSetComplete(int index, object oldValue, object newValue);
    protected virtual void OnValidate(object value);
    public void RemoveAt(int index);
    void ICollection.CopyTo(Array array, int index);
    int IList.Add(object value);
    bool IList.Contains(object value);
    int IList.IndexOf(object value);
    void IList.Insert(int index, object value);
    void IList.Remove(object value);

    // Properties
    [ComVisible(false)]
    public int Capacity { get; set; }
    public int Count { get; }
    protected ArrayList InnerList { get; }
    protected IList List { get; }
    bool ICollection.IsSynchronized { get; }
    object ICollection.SyncRoot { get; }
    bool IList.IsFixedSize { get; }
    bool IList.IsReadOnly { get; }
    object IList.this[int index] { get; set; }
}


Prelevando un esempio dal sito msdn http://msdn2.microsoft.com/en-us/library/system.collections.collectionbase.aspx vediamo come potrebbe essere implementata
una classe che rappresenta una collection di interi a 16 bit.

public class Int16Collection : CollectionBase
{
    public Int16 this[int index]
    {
        get
        {
            return ((Int16)List[index]);
        }
        set
        {
            List[index] = value;
        }
    }

    public int Add(Int16 value)
    {
        return (List.Add(value));
    }

    public int IndexOf(Int16 value)
    {
        return (List.IndexOf(value));
    }

    public void Insert(int index, Int16 value)
    {
        List.Insert(index, value);
    }

    public void Remove(Int16 value)
    {
        List.Remove(value);
    }

    public bool Contains(Int16 value)
    {
        // If value is not of type Int16, this will return false.
        return (List.Contains(value));
    }

    protected override void OnInsert(int index, Object value)
    {
        // Insert additional code to be run only when inserting values.
    }

    protected override void OnRemove(int index, Object value)
    {
        // Insert additional code to be run only when removing values.
    }

    protected override void OnSet(int index, Object oldValue, Object newValue)
    {
        // Insert additional code to be run only when setting values.
    }

    protected override void OnValidate(Object value)
    {
        if (value.GetType() != typeof(System.Int16))
            throw new ArgumentException("value must be of type Int16.", "value");

    }

}


Vedremo in seguito come i generics possono risolvere in modo brillante il problema della creazione di classi fortemente tipizzate.

Print | posted on Sunday, October 28, 2007 4:40 PM | Filed Under [ Exam 70-536 Application Development Foundation ]

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