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ListView.InsertionMark Property

Gets an object used to indicate the expected drop location when an item is dragged within a ListView control.

Namespace:  System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

'Declaration
<BrowsableAttribute(False)> _
Public ReadOnly Property InsertionMark As ListViewInsertionMark

Property Value

Type: System.Windows.Forms.ListViewInsertionMark
A ListViewInsertionMark object representing the insertion mark.

The ListView insertion mark feature lets you visually indicate the expected drop location in a drag-and-drop operation when an item is dragged to a new position. This feature works only when the AutoArrange property is set to true and when the ListView control does not sort the items automatically. To prevent automatic sorting, the Sorting property must be set to SortOrder.None and the View property must be set to View.LargeIcon, View.SmallIcon, or View.Tile. Additionally, the insertion mark feature may not be visible with the ListView grouping feature because the grouping feature orders the items by group membership.

The ListViewInsertionMark class is typically used in a handler for the Control.DragOver or Control.MouseMove event to update the position of the insertion mark as an item is dragged. It is also used in a handler for the Control.DragDrop or Control.MouseUp event to insert a dragged item at the correct location. For more information, see ListViewInsertionMark and How to: Display an Insertion Mark in a Windows Forms ListView Control.

NoteNote

The insertion mark feature is available only on Windows XP and Windows Server 2003 when your application calls the Application.EnableVisualStyles method. On earlier operating systems, any code relating to the insertion mark has no effect and the insertion mark will not appear. As a result, any code that depends on the insertion mark feature might not work correctly. You might want to include code that determines whether this feature is available, and provide alternate functionality when it is unavailable. For example, you might want to bypass all code that implements drag-and-drop item repositioning when running on operating systems that do not support insertion marks.

The insertion mark feature is provided by the same library that provides the operating system themes feature. To check for the availability of this library, call the FeatureSupport.IsPresent(Object) method overload and pass in the OSFeature.Themes value.

The following code example demonstrates how to use the ListView insertion mark feature. This example implements drag-and-drop item reordering using the standard drag events. The position of the insertion mark is updated in a handler for the Control.DragOver event. In this handler, the position of the mouse pointer is compared to the midpoint of the nearest item, and the result is used to determine whether the insertion mark appears to the left or the right of the item.

Imports System
Imports System.Drawing
Imports System.Windows.Forms

Public Class ListViewInsertionMarkExample
    Inherits Form

    Private myListView As ListView

    Public Sub New()
        ' Initialize myListView.
        myListView = New ListView()
        myListView.Dock = DockStyle.Fill
        myListView.View = View.LargeIcon
        myListView.MultiSelect = False
        myListView.ListViewItemSorter = New ListViewIndexComparer()

        ' Initialize the insertion mark.
        myListView.InsertionMark.Color = Color.Green

        ' Add items to myListView.
        myListView.Items.Add("zero")
        myListView.Items.Add("one")
        myListView.Items.Add("two")
        myListView.Items.Add("three")
        myListView.Items.Add("four")
        myListView.Items.Add("five")

        ' Initialize the drag-and-drop operation when running 
        ' under Windows XP or a later operating system. 
        If OSFeature.Feature.IsPresent(OSFeature.Themes)
            myListView.AllowDrop = True 
            AddHandler myListView.ItemDrag, AddressOf myListView_ItemDrag
            AddHandler myListView.DragEnter, AddressOf myListView_DragEnter
            AddHandler myListView.DragOver, AddressOf myListView_DragOver
            AddHandler myListView.DragLeave, AddressOf myListView_DragLeave
            AddHandler myListView.DragDrop, AddressOf myListView_DragDrop
        End If  

        ' Initialize the form. 
        Me.Text = "ListView Insertion Mark Example" 
        Me.Controls.Add(myListView)
    End Sub 'New

    <STAThread()> _
    Shared Sub Main()
        Application.EnableVisualStyles()
        Application.Run(New ListViewInsertionMarkExample())
    End Sub 'Main

    ' Starts the drag-and-drop operation when an item is dragged. 
    Private Sub myListView_ItemDrag(sender As Object, e As ItemDragEventArgs)
        myListView.DoDragDrop(e.Item, DragDropEffects.Move)
    End Sub 'myListView_ItemDrag

    ' Sets the target drop effect. 
    Private Sub myListView_DragEnter(sender As Object, e As DragEventArgs)
        e.Effect = e.AllowedEffect
    End Sub 'myListView_DragEnter

    ' Moves the insertion mark as the item is dragged. 
    Private Sub myListView_DragOver(sender As Object, e As DragEventArgs)
        ' Retrieve the client coordinates of the mouse pointer. 
        Dim targetPoint As Point = myListView.PointToClient(New Point(e.X, e.Y))

        ' Retrieve the index of the item closest to the mouse pointer. 
        Dim targetIndex As Integer = _
            myListView.InsertionMark.NearestIndex(targetPoint)

        ' Confirm that the mouse pointer is not over the dragged item. 
        If targetIndex > -1 Then 
            ' Determine whether the mouse pointer is to the left or 
            ' the right of the midpoint of the closest item and set 
            ' the InsertionMark.AppearsAfterItem property accordingly. 
            Dim itemBounds As Rectangle = myListView.GetItemRect(targetIndex)
            If targetPoint.X > itemBounds.Left + (itemBounds.Width / 2) Then
                myListView.InsertionMark.AppearsAfterItem = True 
            Else
                myListView.InsertionMark.AppearsAfterItem = False 
            End If 
        End If 

        ' Set the location of the insertion mark. If the mouse is 
        ' over the dragged item, the targetIndex value is -1 and 
        ' the insertion mark disappears.
        myListView.InsertionMark.Index = targetIndex
    End Sub 'myListView_DragOver

    ' Removes the insertion mark when the mouse leaves the control. 
    Private Sub myListView_DragLeave(sender As Object, e As EventArgs)
        myListView.InsertionMark.Index = -1
    End Sub 'myListView_DragLeave

    ' Moves the item to the location of the insertion mark. 
    Private Sub myListView_DragDrop(sender As Object, e As DragEventArgs)
        ' Retrieve the index of the insertion mark; 
        Dim targetIndex As Integer = myListView.InsertionMark.Index

        ' If the insertion mark is not visible, exit the method. 
        If targetIndex = -1 Then 
            Return 
        End If  

        ' If the insertion mark is to the right of the item with 
        ' the corresponding index, increment the target index. 
        If myListView.InsertionMark.AppearsAfterItem Then
            targetIndex += 1
        End If  

        ' Retrieve the dragged item. 
        Dim draggedItem As ListViewItem = _
            CType(e.Data.GetData(GetType(ListViewItem)), ListViewItem)

        ' Insert a copy of the dragged item at the target index. 
        ' A copy must be inserted before the original item is removed 
        ' to preserve item index values.
        myListView.Items.Insert(targetIndex, _
            CType(draggedItem.Clone(), ListViewItem))

        ' Remove the original copy of the dragged item.
        myListView.Items.Remove(draggedItem)

    End Sub 'myListView_DragDrop

    ' Sorts ListViewItem objects by index.     
    Private Class ListViewIndexComparer
        Implements System.Collections.IComparer

        Public Function Compare(x As Object, y As Object) As Integer _
            Implements System.Collections.IComparer.Compare
            Return CType(x, ListViewItem).Index - CType(y, ListViewItem).Index
        End Function 'Compare

    End Class 'ListViewIndexComparer

End Class 'ListViewInsertionMarkExample 

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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