How to sort a List (Of T)

  • Thread starter Thread starter Assido
  • Start date Start date
A

Assido

Hello @All,

here is my problem ( code below):

I have a List (of T) containing object s(Key-Object) with 2 properties.

- Name
- Value

An other Object (Section-Calss) provides the List (of Key) as a public member.

So far so good! Now i want to sort the List(of Key) in alphabetical order by
the KeyName.

Can someone tell me how to do it?

------------------------------------------
Code
------------------------------------------
Public Class Form1

Dim oSection As New Section


Private Sub btnGenerateKeys_Click(ByVal sender As System.Object, ByVal e
As System.EventArgs) Handles btnGenerateKeys.Click
' // Call the procedure to fill the oSection.Keys-List with some
objects
GenerateSomeKeys()

' // Fill listbox with the keynames
For Each oKey As Key In oSection.Keys
lsbUnsorted.Items.Add(oKey.Name)
Next

End Sub


' // Generate some lsitentries
Private Sub GenerateSomeKeys()
oSection.Keys.Add(New Key("b", "b"))
oSection.Keys.Add(New Key("c", "c"))
oSection.Keys.Add(New Key("f", "f"))
oSection.Keys.Add(New Key("z", "z"))
oSection.Keys.Add(New Key("a", "a"))
End Sub


Private Sub btnSortList_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles btnSortList.Click
' // Call the sortprocedure
SortListByName()
End Sub


' // Here is the Problem !!! How to do it?
' // Sort listentries by Key.Name
Private Sub SortListByName()

oSection.Keys.Sort()

' // Fill the sorted keynames in the listbox
For Each oKey As Key In oSection.Keys
lsbUnsorted.Items.Add(oKey.Name)
Next

End Sub

End Class

' ###############################
' // The Section-Class
' ###############################
Public Class Section

Public Keys As New List(Of Key)

Sub New()
End Sub
End Class

' ###############################
' // The Key-Class
' ###############################
Public Class Key

Private mName As String
Private mValue As String


Sub New()
End Sub


Sub New(ByVal Name As String, ByVal Value As String)
mName = Name
mValue = Value
End Sub

Public Property Name() As String
Get
Return mName
End Get
Set(ByVal value As String)
mName = value
End Set
End Property


Public Property Value() As String
Get
Return mValue
End Get
Set(ByVal value As String)
mValue = value
End Set
End Property

End Class
 
Assido said:
Hello @All,

here is my problem ( code below):

I have a List (of T) containing object s(Key-Object) with 2 properties.

- Name
- Value

An other Object (Section-Calss) provides the List (of Key) as a public
member.

So far so good! Now i want to sort the List(of Key) in alphabetical order
by
the KeyName.

Can someone tell me how to do it?

------------------------------------------
Code
------------------------------------------
Public Class Form1

Dim oSection As New Section


Private Sub btnGenerateKeys_Click(ByVal sender As System.Object, ByVal
e
As System.EventArgs) Handles btnGenerateKeys.Click
' // Call the procedure to fill the oSection.Keys-List with some
objects
GenerateSomeKeys()

' // Fill listbox with the keynames
For Each oKey As Key In oSection.Keys
lsbUnsorted.Items.Add(oKey.Name)
Next

End Sub


' // Generate some lsitentries
Private Sub GenerateSomeKeys()
oSection.Keys.Add(New Key("b", "b"))
oSection.Keys.Add(New Key("c", "c"))
oSection.Keys.Add(New Key("f", "f"))
oSection.Keys.Add(New Key("z", "z"))
oSection.Keys.Add(New Key("a", "a"))
End Sub


Private Sub btnSortList_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles btnSortList.Click
' // Call the sortprocedure
SortListByName()
End Sub


' // Here is the Problem !!! How to do it?
' // Sort listentries by Key.Name
Private Sub SortListByName()

oSection.Keys.Sort()

' // Fill the sorted keynames in the listbox
For Each oKey As Key In oSection.Keys
lsbUnsorted.Items.Add(oKey.Name)
Next

End Sub

End Class

' ###############################
' // The Section-Class
' ###############################
Public Class Section

Public Keys As New List(Of Key)

Sub New()
End Sub
End Class

' ###############################
' // The Key-Class
' ###############################
Public Class Key

Private mName As String
Private mValue As String


Sub New()
End Sub


Sub New(ByVal Name As String, ByVal Value As String)
mName = Name
mValue = Value
End Sub

Public Property Name() As String
Get
Return mName
End Get
Set(ByVal value As String)
mName = value
End Set
End Property


Public Property Value() As String
Get
Return mValue
End Get
Set(ByVal value As String)
mValue = value
End Set
End Property

End Class
Click to expand...

If you are using VS 2008 and dot.net 3.5 you can use Linq to sort the list.

You would do something like:

oSection.Keys = (from k in oSection.Keys select k order by k.Name).ToList

LS
 
Hello Lloyd Sheen,

thanks for your answer, but i only have VS 2005. :-(

Any other ideas are welcome
 
Assido said:
Hello @All,

here is my problem ( code below):

I have a List (of T) containing object s(Key-Object) with 2 properties.

- Name
- Value

An other Object (Section-Calss) provides the List (of Key) as a public member.

So far so good! Now i want to sort the List(of Key) in alphabetical order by
the KeyName.

Can someone tell me how to do it?

8<


' // Here is the Problem !!! How to do it?
' // Sort listentries by Key.Name
Private Sub SortListByName()

oSection.Keys.Sort()

' // Fill the sorted keynames in the listbox
For Each oKey As Key In oSection.Keys
lsbUnsorted.Items.Add(oKey.Name)
Next

End Sub
Click to expand...

You just have to supply the Sort method with a Comparison:

oSection.Keys.Sort(delegate(Key x, Key y){ return string.Compare(x.Name,
y.Name); })
 
Hello guys,

thanks for your help!

Steve's example worked perfect for me!

Thnaks a lot for your efforts!
 
Steve said:
Not sure if that C# code will play in VB. :)

I found this way to be reasonable:

In class Key, add a shared function:

Public Shared Function CompKeysByName(ByVal X As Key, ByVal Y As Key) As Integer
Return X.Name.CompareTo(Y.Name)
End Function

Then for the sort, do

oSection.Keys.Sort(AddressOf Key.CompKeysByName)
Click to expand...

Yes, you are right, I didn't check the language too carefully before
posting. That would (almost) be the VB version of my code. :)
 
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