Feb 3, 2007 One of the biggest problems with the different types of collections in the .NET Framework, is that they don’t tell you if the collection as been changed or not. If you have
a Collection<int> that has to be persisted to a database, it would be a waste
of resources to do so if the collection hasn’t been changed.
That’s why I found it necessary to override the generic Collection<> class to
provide it with a property called IsChanged. Everytime you add or remove an item in
the collection, the IsChanged property returns true. You can use the property like
so:
if (collectionInstance.IsChanged)
{
//Persist
to database
}
The code
/// <summary>
/// A generic collection with the ability to
/// check if it has been changed.
/// </summary>
[System.Serializable]
public class StateCollection<T> : System.Collections.ObjectModel.Collection<T>
{
#region Base
overrides
/// <summary>
/// Inserts an element into the collection at the specified index and marks it changed.
/// </summary>
protected override void InsertItem(int index, T item)
{
base.InsertItem(index, item);
_IsChanged = true;
}
/// <summary>
/// Removes all the items in the collection and marks it changed.
/// </summary>
protected override void ClearItems()
{
base.ClearItems();
_IsChanged = true;
}
/// <summary>
/// Removes the element at the specified index and marks the collection changed.
/// </summary>
protected override void RemoveItem(int index)
{
base.RemoveItem(index);
_IsChanged = true;
}
/// <summary>
/// Replaces the element at the specified index and marks the collection changed.
/// </summary>
protected override void SetItem(int index, T item)
{
base.SetItem(index, item);
_IsChanged = true;
}
#endregion
private bool _IsChanged;
/// <summary>
/// Gets if this object's data has been changed.
/// </summary>
/// <returns>A value indicating if this object's data has been changed.</returns>
public virtual bool IsChanged
{
get { return _IsChanged; }
set { _IsChanged = value; }
}
}
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