Sorting an Arraylist of Objects

[Derek Martin]

Hi there, I've asked before but never got an answer that could get me
completely to where I was heading. I have an arraylist that contains
defined objects and I would like to sort this arraylist based on the values
of one of the object's members.

Here is a bit of code to illustrate my setup:

Object construction and insertion:
Dim entity As New entityobjects(e ntitynamenodeli st(i).InnerXml,
typenodelist(i) .InnerXml, ...)
entityarraylist .add(entity)
----------------------------------------------------------------------------------------------
Object definition class:
Public Class entityobjects
Protected m_entityid As String
Protected m_entityname As String
Protected m_type As String
...

Public Sub New(ByVal entityname As String, ByVal type As String ...)
Me.entityname = entityname
Me.type = type
...
End Sub
----------------------------------------------------------------------------------------------

Now, I would like to list out the objects sorted by entityname:

'What can I put here to sort these???

for each entity as object in entityarraylist
richtextbox1.ap pendtext(entity .toString()) 'toString is overridden here
in the object class
next
----------------------------------------------------------------------------------------------

I have read that I can implement icomparable or icomparer in the object
class but can't quite put my finger on how?

Thank you!
Derek





--
Derek Martin

[Scott Allen]

Re: Sorting an Arraylist of Objects

Hi Derek:

I have an article here that may be of some help:

http://odetocode.com/Articles/203.aspx

--
Scott

http://www.OdeToCode.com/blogs/scott/

On Thu, 23 Dec 2004 09:41:39 -0600, "Derek Martin"
<dmj2195@DONTSP AMMEokstateDOT. edu> wrote:
[color=blue]
>Hi there, I've asked before but never got an answer that could get me
>completely to where I was heading. I have an arraylist that contains
>defined objects and I would like to sort this arraylist based on the values
>of one of the object's members.
>
>Here is a bit of code to illustrate my setup:
>
>Object construction and insertion:
>Dim entity As New entityobjects(e ntitynamenodeli st(i).InnerXml,
>typenodelist(i ).InnerXml, ...)
>entityarraylis t.add(entity)
>----------------------------------------------------------------------------------------------
>Object definition class:
>Public Class entityobjects
> Protected m_entityid As String
> Protected m_entityname As String
> Protected m_type As String
> ...
>
>Public Sub New(ByVal entityname As String, ByVal type As String ...)
> Me.entityname = entityname
> Me.type = type
> ...
>End Sub
>----------------------------------------------------------------------------------------------
>
>Now, I would like to list out the objects sorted by entityname:
>
>'What can I put here to sort these???
>
>for each entity as object in entityarraylist
> richtextbox1.ap pendtext(entity .toString()) 'toString is overridden here
>in the object class
>next
>----------------------------------------------------------------------------------------------
>
>I have read that I can implement icomparable or icomparer in the object
>class but can't quite put my finger on how?
>
>Thank you!
>Derek[/color]

[Derek Martin]

Re: Sorting an Arraylist of Objects

Thanks Scott, I will investigate!

Derek



"Scott Allen" <bitmask@[nospam].fred.net> wrote in message
news:nlsls0tdor 749sc8cmibq668e ekc23g4ma@4ax.c om...[color=blue]
> Hi Derek:
>
> I have an article here that may be of some help:
> http://odetocode.com/Articles/203.aspx
>
> --
> Scott
> http://www.OdeToCode.com/blogs/scott/
>
> On Thu, 23 Dec 2004 09:41:39 -0600, "Derek Martin"
> <dmj2195@DONTSP AMMEokstateDOT. edu> wrote:
>[color=green]
>>Hi there, I've asked before but never got an answer that could get me
>>completely to where I was heading. I have an arraylist that contains
>>defined objects and I would like to sort this arraylist based on the
>>values
>>of one of the object's members.
>>
>>Here is a bit of code to illustrate my setup:
>>
>>Object construction and insertion:
>>Dim entity As New entityobjects(e ntitynamenodeli st(i).InnerXml,
>>typenodelist( i).InnerXml, ...)
>>entityarrayli st.add(entity)
>>----------------------------------------------------------------------------------------------
>>Object definition class:
>>Public Class entityobjects
>> Protected m_entityid As String
>> Protected m_entityname As String
>> Protected m_type As String
>> ...
>>
>>Public Sub New(ByVal entityname As String, ByVal type As String ...)
>> Me.entityname = entityname
>> Me.type = type
>> ...
>>End Sub
>>----------------------------------------------------------------------------------------------
>>
>>Now, I would like to list out the objects sorted by entityname:
>>
>>'What can I put here to sort these???
>>
>>for each entity as object in entityarraylist
>> richtextbox1.ap pendtext(entity .toString()) 'toString is overridden
>> here
>>in the object class
>>next
>>----------------------------------------------------------------------------------------------
>>
>>I have read that I can implement icomparable or icomparer in the object
>>class but can't quite put my finger on how?
>>
>>Thank you!
>>Derek[/color]
>[/color]

[Mythran]

Re: Sorting an Arraylist of Objects


"Derek Martin" <dmj2195@DONTSP AMMEokstateDOT. edu> wrote in message
news:%23aV5lXQ6 EHA.3908@TK2MSF TNGP12.phx.gbl. ..[color=blue]
> Hi there, I've asked before but never got an answer that could get me
> completely to where I was heading. I have an arraylist that contains
> defined objects and I would like to sort this arraylist based on the
> values of one of the object's members.
>[/color]

Hope the following Console application example helps :)


Public Module Main
<STAThread()> _
Public Sub Main()
Dim list As ArrayList = New ArrayList()
list.Add(New Entity("abcdfz" ))
list.Add(New Entity("bacdfz" ))
list.Add(New Entity("zfdcba" ))
list.Add(New Entity("fdadsf" ))
list.Add(New Entity("akjjlk" ))
list.Add(New Entity("ieiojd" ))
list.Add(New Entity("adfklas jfdlkajs"))

list.Sort()

For Each obj As Entity In list
Console.WriteLi ne(obj.EntityId )
Next
End Sub

End Module

Public Class Entity
Implements IComparable

Private mEntityId As String

Public Property EntityId() As String
Get
Return mEntityId
End Get
Set
mEntityId = Value
End Set
End Property

Public Sub New(ByVal EntityId As String)
mEntityId = EntityId
End Sub

Public Function CompareTo(ByVal obj As Object) As Integer Implements
System.ICompara ble.CompareTo
If TypeOf obj Is Entity
Dim tmp As Entity = DirectCast(obj, Entity)
Return mEntityId.Compa reTo(tmp.Entity Id)
End If

Throw New ArgumentExcepti on("The argument is not an Entity.")
End Function
End Class