searching multi - Item arraylist

[Jon Paal]

how can I search for a value in a multi - item arraylist to prevent adding duplicates ?

[Anthony Merante]

Hey Jon,

To prevent dups i'll use the Contains Method of the Arraylist like

if(!myArrayList.Contains(obj))
{
myArrayList.Add(obj);
}

Hope thats what u were looking for,
T
"Jon Paal" <Jon[ nospam ]Paal @ everywhere dot com> wrote in message
news:%2****************@TK2MSFTNGP09.phx.gbl...

how can I search for a value in a multi - item arraylist to prevent adding
duplicates ?

[Jon Paal]

it's not working for me . I add a new item as multi-dimensional like this:

"arrChartList.Add( New ChartItem (Unit,Amount ) ) "
How do I test for existence of ChartItem ?

I tried but no success with :

If Not arrChartList.Contains(ChartItem ( Unit,Amount ) ) Then
arrChartList.Add( New ChartItem (Unit,Amount ) )
End If

"Anthony Merante" <am******@hotmail.com> wrote in message news:%2****************@TK2MSFTNGP11.phx.gbl...

Hey Jon,

To prevent dups i'll use the Contains Method of the Arraylist like

if(!myArrayList.Contains(obj))
{
myArrayList.Add(obj);
}

Hope thats what u were looking for,
T
"Jon Paal" <Jon[ nospam ]Paal @ everywhere dot com> wrote in message news:%2****************@TK2MSFTNGP09.phx.gbl...

how can I search for a value in a multi - item arraylist to prevent adding duplicates ?

[Laurent Bugnion]

Hi,

Jon Paal wrote:

it's not working for me . I add a new item as multi-dimensional like this:

"arrChartList.Add( New ChartItem (Unit,Amount ) ) "
How do I test for existence of ChartItem ?

I tried but no success with :

If Not arrChartList.Contains(ChartItem ( Unit,Amount ) ) Then
arrChartList.Add( New ChartItem (Unit,Amount ) )
End If

When you use the "Contains" method to look an item up, the item you pass
to the Contains method must be a reference to the *same* object stored
in the ArrayList. In other words, the '==' operator must return true.
For a string, you can use a different object with the same value,
because the '==' operator works this way for strings. But for an object,
it doesnt' work.

MyObject obj1 = new MyObject( 3, 4, 5 );
MyObject obj2 = new MyObject( 3, 4, 5 );
obj1 == obj2; // this is false, unless you override the '==' operator to
return a different value.

So... to solve your problem, there are different ways. One is to save a
reference to the ChartItem you create somewhere in your code, and to use
this reference to check if it was added to the ArrayList already, or you
can use a Hashtable and check for the Key rather than for the value
itself. Since the key can be pretty much anything, you can use for
example a string representation of your ChartItem, which makes things
easier.

HTH,
Laurent
--
Laurent Bugnion, GalaSoft
Software engineering: http://www.galasoft-LB.ch
Private/Malaysia: http://mypage.bluewin.ch/lbugnion
Support children in Calcutta: http://www.calcutta-espoir.ch

[Jon Paal]

that helps, I'll switch to hash tables.

thanks to all
"Laurent Bugnion" <lb******@bluewin.ch> wrote in message news:44********@news.bluewin.ch...

Hi,

Jon Paal wrote:

it's not working for me . I add a new item as multi-dimensional like this:

"arrChartList.Add( New ChartItem (Unit,Amount ) ) "
How do I test for existence of ChartItem ?

I tried but no success with :

If Not arrChartList.Contains(ChartItem ( Unit,Amount ) ) Then
arrChartList.Add( New ChartItem (Unit,Amount ) )
End If

When you use the "Contains" method to look an item up, the item you pass to the Contains method must be a reference to the *same*
object stored in the ArrayList. In other words, the '==' operator must return true. For a string, you can use a different object
with the same value, because the '==' operator works this way for strings. But for an object, it doesnt' work.

MyObject obj1 = new MyObject( 3, 4, 5 );
MyObject obj2 = new MyObject( 3, 4, 5 );
obj1 == obj2; // this is false, unless you override the '==' operator to return a different value.

So... to solve your problem, there are different ways. One is to save a reference to the ChartItem you create somewhere in your
code, and to use this reference to check if it was added to the ArrayList already, or you can use a Hashtable and check for the
Key rather than for the value itself. Since the key can be pretty much anything, you can use for example a string representation
of your ChartItem, which makes things easier.

HTH,
Laurent
--
Laurent Bugnion, GalaSoft
Software engineering: http://www.galasoft-LB.ch
Private/Malaysia: http://mypage.bluewin.ch/lbugnion
Support children in Calcutta: http://www.calcutta-espoir.ch