about List and InnerList in class CollectionBase

[Tony]

Hello!

Here I have a collection class Cards which is derived from the Base class
CollectionBase.
This class Cards is a container for Card object.
Now to my question at the bottom of this class we have a method called
Contains.
It gived the same result to use InnerList and List in this method Contains.
I can also just replace List with InnerList in the method Add and it works.

So is the InnerList the same as List because I can use whichever of these
two ?


public class Cards : CollectionBase
{
public Cards() {}

public void Add(Card newCard)
{
List.Add(newCard);
}

public void Remove(Card oldCard)
{
List.Remove(oldCard);
}

public Card this[int cardIndex]
{
get { return (Card)List[cardIndex]; }
set { List[cardIndex] = value; }
}

public void CopyTo(Cards targetCards)
{
for (int index = 0; index < this.Count; index++)
targetCards[index] = this[index];
}

public bool Contains(Card card)
{
bool test1,test2;
test1 = InnerList.Contains(card);
test2 = List.Contains(card);
return true;

}
}

//Tony

 

[Morten Wennevik [C# MVP]]

Hi Tony,

The difference is that InnerList returns a losely connected ArrayList which
will not trigger the On* methods when manipulated. List will return an IList
which will trigger the On* methods when manipulated.

class MyCollection : CollectionBase
{
protected override void OnInsert(int index, object value)
{
base.OnInsert(index, value);
}

public void Add(object value)
{
List.Add(value); // Will trigger OnInsert
InnerList.Add(value); // Will not trigger OnInsert
}
}

 

[Tony]

Hello!

Will it be some performance effect if a use List insted of InnerList when
not having any OnInsert(...)

//Tony

Hi Tony,

The difference is that InnerList returns a losely connected ArrayList which
will not trigger the On* methods when manipulated. List will return an IList
which will trigger the On* methods when manipulated.

class MyCollection : CollectionBase
{
protected override void OnInsert(int index, object value)
{
base.OnInsert(index, value);
}

public void Add(object value)
{
List.Add(value); // Will trigger OnInsert
InnerList.Add(value); // Will not trigger OnInsert
}
}


--
Happy Coding!
Morten Wennevik [C# MVP]

Hello!

Here I have a collection class Cards which is derived from the Base class
CollectionBase.
This class Cards is a container for Card object.
Now to my question at the bottom of this class we have a method called
Contains.
It gived the same result to use InnerList and List in this method Contains.
I can also just replace List with InnerList in the method Add and it works.

So is the InnerList the same as List because I can use whichever of these
two ?


public class Cards : CollectionBase
{
public Cards() {}

public void Add(Card newCard)
{
List.Add(newCard);
}

public void Remove(Card oldCard)
{
List.Remove(oldCard);
}

public Card this[int cardIndex]
{
get { return (Card)List[cardIndex]; }
set { List[cardIndex] = value; }
}

public void CopyTo(Cards targetCards)
{
for (int index = 0; index < this.Count; index++)
targetCards[index] = this[index];
}

public bool Contains(Card card)
{
bool test1,test2;
test1 = InnerList.Contains(card);
test2 = List.Contains(card);
return true;

}
}

//Tony

 

[Morten Wennevik [C# MVP]]

Hello!

Will it be some performance effect if a use List insted of InnerList when
not having any OnInsert(...)

//Tony

There is a tiny overhead when using List vs InnerList, but it is only
visible when using large collections (>1 000 000 items) and even then
measurable in milliseconds. Most likely this wouldn't be the bottleneck in
performance issues even then. If you need to override
CollectionBase-behaviour, use List, if you don't, or if you want to
circumvent overridden behaviour, use InnerList.

 

[Tony]

Hello!!

I just wonder does this OnInsert(...)
actually do anything when I'm not overriding it.

//Tony

 

[Morten Wennevik [C# MVP]]

Hi Tony,

I'm not sure if anything happens during the On* events. If you are using
Visual Studio 2008 you can easily see for yourself by stepping into framework
code. See the article below for an example on how to configure Visual Studio
2008 to enable this

http://blogs.msdn.com/sburke/archiv...tudio-to-debug-net-framework-source-code.aspx