// *** Protected Methods ***
protected void PostUpdate(DataListUpdate update)
{
foreach (IUpdatableCollection collection in updateSubscriptions)
{
collection.Update(update);
}
}
// *** Private Methods ***
private void ProcessUpdate_Add(DataListUpdate update)
{
// If the update is outside of the bounds of the 'count' then simply consume the event
if (update.Index >= count)
{
return;
}
// Forward the 'Add' update to any subscribers
// NB: The number of items added may need to be trimmed if they will exceed the bounds of the Take
int itemsAdded = Math.Min(update.Count, count - update.Index);
PostUpdate(new DataListUpdate(DataListUpdateAction.Add, update.Index, itemsAdded));
// If the 'Add' operation has pushed some items outside of the bounds of the Take then these will need to be removed
int oldCount = Math.Min(sourceCount, count);
int itemsRemoved = oldCount + itemsAdded - count;
if (itemsRemoved > 0)
{
PostUpdate(new DataListUpdate(DataListUpdateAction.Remove, count, itemsRemoved));
}
// Set the last known source count
sourceCount += update.Count;
}
private void ProcessUpdate_Remove(DataListUpdate update)
{
// If the update is outside of the bounds of the 'count' then simply consume the event
if (update.Index >= count)
{
return;
}
// Forward the 'Remove' update to any subscribers
// NB: The number of items removed may need to be trimmed if they exceed the bounds of the Take
int itemsRemoved = Math.Min(update.Count, count - update.Index);
PostUpdate(new DataListUpdate(DataListUpdateAction.Remove, update.Index, itemsRemoved));
// If the 'Remove' operation has pulled in some items outside of the bounds of the Take then these will need to be added
int itemsAvailable = sourceCount - Math.Max(update.Index + update.Count, count);
int itemsAdded = Math.Min(itemsRemoved, itemsAvailable);
if (itemsAdded > 0)
{
PostUpdate(new DataListUpdate(DataListUpdateAction.Add, count - itemsRemoved, itemsAdded));
}
// Set the last known source count
sourceCount -= update.Count;
}
protected virtual void ProcessUpdate(DataListUpdate update)
{
// Unsubscribe from future updates if all subscribers have been garbage collected or removed
UnsubscribeFromSourceIfNoSubscribers();
// If the derived class does not implement ProcessUpdate then simply forward the update
PostUpdate(update);
}
private void Update_Add(DataListUpdate update)
{
// If the entire update is outside of the visible collection then ignore it
if (update.Index > currentCount)
{
return;
}
currentCount += update.Count;
base.OnItemsAdded(update.Index, update.Count);
}
private void Update_Remove(DataListUpdate update)
{
// If the entire update is outside of the visible collection then ignore it
if (update.Index >= currentCount)
{
return;
}
// If the update overlaps the boundary of the visible collection then only remove visible items
int removedItemCount = Math.Min(update.Count, currentCount - update.Index);
currentCount -= removedItemCount;
base.OnItemsRemoved(update.Index, removedItemCount);
}
protected override void ProcessUpdate(DataListUpdate update)
{
switch (update.Action)
{
case DataListUpdateAction.Add:
ProcessUpdate_Add(update);
break;
case DataListUpdateAction.Remove:
ProcessUpdate_Remove(update);
break;
default:
PostUpdate(update);
break;
}
}
// *** IUpdatableCollection Members ***
void IUpdatableCollection.Update(DataListUpdate update)
{
switch (update.Action)
{
case DataListUpdateAction.Add:
base.OnItemsAdded(update.Index, update.Count);
break;
case DataListUpdateAction.Remove:
base.OnItemsRemoved(update.Index, update.Count);
break;
case DataListUpdateAction.Reset:
base.Reset();
break;
}
}
// *** IUpdatableCollection Members ***
void IUpdatableCollection.Update(DataListUpdate update)
{
switch (update.Action)
{
case DataListUpdateAction.Add:
Update_Add(update);
break;
case DataListUpdateAction.Remove:
Update_Remove(update);
break;
case DataListUpdateAction.Reset:
Update_Reset();
break;
}
}
// *** Private Methods ***
private void ProcessUpdate_Add(DataListUpdate update)
{
// Determine the index that the subscribers will see items added at
// - If the update is before the start of the window, then items will flow into the start
// - If the update is within the window then the items will be placed there
int oldCount = Math.Max(0, sourceCount - count);
int newCount = Math.Max(0, sourceCount + update.Count - count);
if (oldCount != newCount)
{
int addIndex = Math.Max(0, update.Index - count);
PostUpdate(new DataListUpdate(DataListUpdateAction.Add, addIndex, newCount - oldCount));
}
// Set the last known source count
sourceCount += update.Count;
}
private void ProcessUpdate_Remove(DataListUpdate update)
{
// Determine the index that the subscribers will see items removed from
// - If the update is before the start of the window, then items will flow out from the start
// - If the update is within the window then the items will be removed there
int oldCount = Math.Max(0, sourceCount - count);
int newCount = Math.Max(0, sourceCount - update.Count - count);
if (oldCount != newCount)
{
int removeIndex = Math.Max(0, update.Index - count);
PostUpdate(new DataListUpdate(DataListUpdateAction.Remove, removeIndex, oldCount - newCount));
}
// Set the last known source count
sourceCount += update.Count;
}
// *** IUpdatableCollection Methods ***
void IUpdatableCollection.Update(DataListUpdate update)
{
// Process the update to perform any side-effects or conversions required and forward to any subscribers
ProcessUpdate(update);
}
public void Constructor_Remove_SetsCountProperty()
{
DataListUpdate update = new DataListUpdate(DataListUpdateAction.Remove, 2, 5);
Assert.AreEqual(5, update.Count);
}
public void Constructor_Remove_SetsIndexProperty()
{
DataListUpdate update = new DataListUpdate(DataListUpdateAction.Remove, 2, 5);
Assert.AreEqual(2, update.Index);
}
public void Constructor_Add_SetsActionProperty()
{
DataListUpdate update = new DataListUpdate(DataListUpdateAction.Add, 2, 5);
Assert.AreEqual(DataListUpdateAction.Add, update.Action);
}
public void Constructor_Reset_SetsActionProperty()
{
DataListUpdate update = new DataListUpdate(DataListUpdateAction.Reset);
Assert.AreEqual(DataListUpdateAction.Reset, update.Action);
}