What entity get ListViewItems sorted by?

[RaGa68]

Hello :-)

I have built a ListView and filled it like this (simplified pseudo code):

Dim clm(3) As String

For i = 0 To rows

                clm(0) = something(i)
                clm(1) = anything(i)
                clm(2) = stuff(i)

                Dim itm As ListViewItem = New ListViewItem(clm)

                myListView.Items.Add(itm)

Next

Now, when the myListView.Sort ing property is set to anything else but "None" the listview will be sorted, ascending or descending. But what determines by which entity it will be sorted?

The MS docs only say:

The Sorting property allows you to specify whether or not items are sorted in the ListView control. By default, no sorting is performed. When the Sorting property is set to Ascending or Descending, the items in the ListView are sorted automatically in ascending alphabetical order (when the property is set to Ascending) or descending alphabetical order (when the property is set to Descending).

1. The "items" are an array each. So by which member of the array will the ListView be sorted?
2. Can I set a key, and would it make sorting quicker (currently taking a painful 5+ minutes for a 23000 items ListView)?
3. The ListViewItem.Na me property is often referred to as a 'key', but with the above fill method this property will remain an emtpy string. Does it make any sense to set it to some value?

Grateful for any insight and help
- Ralph

[SioSio]

To have ListView items sorted automatically, set the ListView.Sortin g property to SortOrder.Ascen ding or SortOrder.Desce nding.

myListView.Sorting = System.Windows.Forms.SortOrder.Ascending

However, with this method, sub-items cannot be compared and sorted, and numbers and times cannot be sorted correctly.
(Only the first item is sorted.)
To solve these problems, set the ListView.ListVi ewItemSorter property to an instance of a class that implements the IComparer interface that defines the arrangement.

Public Class ListViewItemComparer
    Implements IComparer
    Private _column As Integer
	Private _Ascend As Boolean
	Public Sub New(ByVal col As Integer, ByVal Ascend As Boolean)
		_column = col
		_Ascend = Ascend
	End Sub
	
	Public Function CompareTo(ByVal x As Object, ByVal y As Object) _
		As Integer Implements System.Collections.IComparer.Compare
		'Get the ListViewItem
		Dim itemx As ListViewItem = CType(x, ListViewItem)
		Dim itemy As ListViewItem = CType(y, ListViewItem)
		
		If IsNumeric(itemx.SubItems(_column).Text) = True Then
			Dim xx As Double
			Dim yy As Double
			Dim resulta As Boolean = Double.TryParse(itemx.SubItems(_column).Text, xx)
			Dim resultb As Boolean = Double.TryParse(itemy.SubItems(_column).Text, yy)
			If _Ascend = True then
				Return xx.CompareTo(yy)
			Else
				Return yy.CompareTo(xx)
			End If
		Else
			If _Ascend = True then
				Return itemx.SubItems(_column).Text.CompareTo(itemy.SubItems(_column).Text)
			Else
				Return itemy.SubItems(_column).Text.CompareTo(itemx.SubItems(_column).Text)
			End If
		End If
	End Function
End Class

Public Partial Class MainForm
	Dim AD As Boolean = True
	Public Sub New()
		Me.InitializeComponent()
		myListView.View = View.Details
		'Set ColumnClick event handler
		AddHandler myListView.ColumnClick, _
			AddressOf ListView1_ColumnClick
		
		Dim i As Long
		Dim clm(3) As String
		Dim rn As New System.Random()
		Dim rc As New System.Random()
		For i = 0 To 22999
			Clm(0) = ChrW(rc.Next(AscW("A"), AscW("Z") + 1)) & ChrW(rc.Next(AscW("A"), AscW("Z") + 1)) & ChrW(rc.Next(AscW("A"), AscW("Z") + 1))
			clm(1) = rn.Next().ToString
			clm(2) = i.ToString
			Dim itm As ListViewItem = New ListViewItem(clm)
			myListView.Items.Add(itm)
		Next i
		
		'Add columns
		myListView.Columns.Add("String", 100, HorizontalAlignment.Left)
		myListView.Columns.Add("Numeric1", 100, HorizontalAlignment.Right)
		myListView.Columns.Add("Numeric2", 100, HorizontalAlignment.Right)
		'Sort Ascending
		myListView.Sorting = System.Windows.Forms.SortOrder.Ascending
	End Sub
	
	Private Sub ListView1_ColumnClick(ByVal sender As Object, ByVal e As ColumnClickEventArgs)
		myListView.ListViewItemSorter = New ListViewItemComparer(e.Column, AD)
		If AD = True Then
			AD = False
		Else
			AD = True
		End If
	End Sub
End Class

The code above sorts the items in ascending / descending order by clicking on the column header.

[madankarmukta]

Please restrict the sort order to some value.It also constrained to datatype.

Let me know the datatype please.