CodeProject: Drag and Drop List View. Free source code and programming help

An upcoming application at work required me to have drag and drop functionality between many different ListViews or DataGrids. When I got word, I decided to start searching the Internet and find a pre-existing free control that I could use. My personal requirements were that the ListView or DataGrid needed to have the ability to move rows around within its own control, but also allow me to move rows to other controls. My initial sorting pointed me towards Drag and Drop ListView row reordering by David Boland. As his control allowed users to reorder items in a ListView, it lacked support for moving to other ListViews as well as letting the user know where the new rows are to be placed. This control is somewhat similar to David's, however, it was rewritten only using David's code as a reference.

Using the Code

The DragAndDropListView control inherits from ListView, and provides native support for dragging and dropping ListItems to reorder them or move them to other DragAndDropListView controls. Because it needs to utilize Drag and Drop functionality, I had to override the OnDragDrop, OnDragOver, OnDragEnter, OnItemDrag, OnLostFocus, and OnDragLeave to provide the functionality.

When an item is selected and started to be dragged, OnItemDrag gets called which starts the Drag and Drop functionality by retrieving the control it originates from as well as the selected items. Both of these are stored in a private class that is passed around in the data of the drag and drop events.

As the user moves the selected list items over the ListView, OnDragOver is called. This method basically determines if the selected items to be dragged & dropped can actually be dragged & dropped. By checking to see if the item it's currently hovering over is not one of the list items being moved, it either displays the move cursor or denied cursor. If the user is trying to drop the items into an area that doesn't have a list item, it will still allow you, thus allowing you to place and reorder items in any order.

One of the really cool things that I wanted to do, was to add a line either above or below the hovered list item, however, this really didn't pose an easy feat at first. To figure this out, I had 2 actual implementations of creating the line, 1 for when you were hovering over a list item, and 1 for when you were in an empty area. When you were hovering over a list item, the line needed to be added between that item and the item above it. If the user is currently over the empty area, and items existed, then the line would be added to the bottom of the very last item. Below is the code that shows how to add the line and arrows on both side:

Previous versions of this article stated that lines would only be drawn if it was in Details or Line mode, however this updated version includes both Small Icon List and Large Icon List replacing horizontal lines with vertical lines. The demo has also been updated, so you can test this method out as well.

As the user is dragging the selected items around the form, OnLostFocus and OnDragLeave are utilized to invalidate the form so the drawn lines are erased.

Lastly, OnDragDrop is called whenever the user drops the selected items into a DragAndDropListView. This method determines if the items to be dropped are from the current DragAndDropListView or from another DragAndDropListView. At which point, the items are appended to the end, or above the hovered item. Finally, the selected items are removed from the respective DragAndDropListView.

Known Problems

Version History

References

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Retaining tag or name property of item after drag-drop reorder

honcho26

10:41 12 Jun '08

Hello!
I'm trying to use the DragNDropListView for a data-driven list. Since there is no key property for a ListViewItem like you might find in a dropdown listbox, I need to store the underlying data key in some other property. I've been saving it in either the Tag or Name property of each item.

However, when using the DragNDropListView control, after dragging an item, it's tag and name properties are blank. I have looked through the source code at where items are created, and my only guess is that when it inserts items back into the listview after a drag, only the textual identifier of the ListViewItem is retained. I've tried to set the .tag and .name properties of the item before it is inserted, but to no avail.

Can anyone make a recommendation on how to tweak the code so that my underlying data key is retained through a drag-drop operation?

Rich Gunther
rich@ovostudios.com

4.00/5

FOUND THE ANSWER! Re: Retaining tag or name property of item after drag-drop reorder

honcho26

11:45 12 Jun '08

For anyone who is interested in the answer to my question

I did some experimentation with the code underlying the DragAndDrop list, and found a way to ensure that at least the Name property of each ListViewItem persists through a drag-reorder. What I changed in the code is probably overkill: I explicitly set the Name property, cloned each ListViewItem instead of simply doing an add, and used the Items.Add constructor that specifies the name of the ListViewItem. It's important to do this both when you gather the dragItems in GetDataForDragDrop, as well as in the onDragDrop event (both for the insert and add portions).

If you use a listview to display a textual identifier underlaid by a unique data key, this is a great way to implement it.

I've tested this, and it does indeed retain the Name properties of each ListViewItem. Here is the edited code:

using System;
using System.Drawing;
using System.Collections;
using System.Windows.Forms;
using System.ComponentModel;

namespace DragNDrop
{
public class DragAndDropListView : ListView
{
#region Private Members

private ListViewItem m_previousItem;
private bool m_allowReorder;
private Color m_lineColor;

#endregion

#region Public Properties

[Category("Behavior")]
public bool AllowReorder
{
get { return m_allowReorder; }
set { m_allowReorder = value; }
}

[Category("Appearance")]
public Color LineColor
{
get { return m_lineColor; }
set { m_lineColor = value; }
}

#endregion

#region Protected and Public Methods

public DragAndDropListView() : base()
{
m_allowReorder = true;
m_lineColor = Color.Red;
}

protected override void OnDragDrop(DragEventArgs drgevent)
{
if(!m_allowReorder)
{
base.OnDragDrop(drgevent);
return;
}

// get the currently hovered row that the items will be dragged to
Point clientPoint = base.PointToClient(new Point(drgevent.X, drgevent.Y));
ListViewItem hoverItem = base.GetItemAt(clientPoint.X, clientPoint.Y);

if(!drgevent.Data.GetDataPresent(typeof(DragItemData).ToString()) || ((DragItemData) drgevent.Data.GetData(typeof(DragItemData).ToString())).ListView == null || ((DragItemData) drgevent.Data.GetData(typeof(DragItemData).ToString())).DragItems.Count == 0)
return;

// retrieve the drag item data
DragItemData data = (DragItemData) drgevent.Data.GetData(typeof(DragItemData).ToString());

if(hoverItem == null)
{
// the user does not wish to re-order the items, just append to the end
for(int i=0; i {
ListViewItem newItem = (ListViewItem)((ListViewItem)data.DragItems[i]).Clone();
newItem.Name = ((ListViewItem)data.DragItems[i]).Name;
base.Items.Add(newItem.Name, newItem.Text, "");
}
}
else
{
// the user wishes to re-order the items

// get the index of the hover item
int hoverIndex = hoverItem.Index;

// determine if the items to be dropped are from
// this list view. If they are, perform a hack
// to increment the hover index so that the items
// get moved properly.
if(this == data.ListView)
{
if(hoverIndex > base.SelectedItems[0].Index)
hoverIndex++;
}

// insert the new items into the list view
// by inserting the items reversely from the array list
for(int i=data.DragItems.Count - 1; i >= 0; i--)
{
ListViewItem newItem = (ListViewItem) ((ListViewItem) data.DragItems[i]).Clone();
newItem.Name = ((ListViewItem)data.DragItems[i]).Name;
base.Items.Insert(hoverIndex, newItem);

}
}

// remove all the selected items from the previous list view
// if the list view was found
if(data.ListView != null)
{
foreach(ListViewItem itemToRemove in data.ListView.SelectedItems)
{
data.ListView.Items.Remove(itemToRemove);
}
}

// set the back color of the previous item, then nullify it
if(m_previousItem != null)
{
m_previousItem = null;
}

this.Invalidate();

// call the base on drag drop to raise the event
base.OnDragDrop (drgevent);
}

protected override void OnDragOver(DragEventArgs drgevent)
{
if(!m_allowReorder)
{
base.OnDragOver(drgevent);
return;
}

if(!drgevent.Data.GetDataPresent(typeof(DragItemData).ToString()))
{
// the item(s) being dragged do not have any data associated
drgevent.Effect = DragDropEffects.None;
return;
}

if(base.Items.Count > 0)
{
// get the currently hovered row that the items will be dragged to
Point clientPoint = base.PointToClient(new Point(drgevent.X, drgevent.Y));
ListViewItem hoverItem = base.GetItemAt(clientPoint.X, clientPoint.Y);

Graphics g = this.CreateGraphics();

if(hoverItem == null)
{
//MessageBox.Show(base.GetChildAtPoint(new Point(clientPoint.X, clientPoint.Y)).GetType().ToString());

// no item was found, so no drop should take place
drgevent.Effect = DragDropEffects.Move;

if(m_previousItem != null)
{
m_previousItem = null;
Invalidate();
}

hoverItem = base.Items[base.Items.Count - 1];

if(this.View == View.Details || this.View == View.List)
{
g.DrawLine(new Pen(m_lineColor, 2), new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + hoverItem.Bounds.Height), new Point(hoverItem.Bounds.X + this.Bounds.Width, hoverItem.Bounds.Y + hoverItem.Bounds.Height));
g.FillPolygon(new SolidBrush(m_lineColor), new Point[] {new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + hoverItem.Bounds.Height - 5), new Point(hoverItem.Bounds.X + 5, hoverItem.Bounds.Y + hoverItem.Bounds.Height), new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + hoverItem.Bounds.Height + 5)});
g.FillPolygon(new SolidBrush(m_lineColor), new Point[] {new Point(this.Bounds.Width - 4, hoverItem.Bounds.Y + hoverItem.Bounds.Height - 5), new Point(this.Bounds.Width - 9, hoverItem.Bounds.Y + hoverItem.Bounds.Height), new Point(this.Bounds.Width - 4, hoverItem.Bounds.Y + hoverItem.Bounds.Height + 5)});
}
else
{
g.DrawLine(new Pen(m_lineColor, 2), new Point(hoverItem.Bounds.X + hoverItem.Bounds.Width, hoverItem.Bounds.Y), new Point(hoverItem.Bounds.X + hoverItem.Bounds.Width, hoverItem.Bounds.Y + hoverItem.Bounds.Height));
g.FillPolygon(new SolidBrush(m_lineColor), new Point[] {new Point(hoverItem.Bounds.X + hoverItem.Bounds.Width - 5, hoverItem.Bounds.Y), new Point(hoverItem.Bounds.X + hoverItem.Bounds.Width + 5, hoverItem.Bounds.Y), new Point(hoverItem.Bounds.X + hoverItem.Bounds.Width, hoverItem.Bounds.Y + 5)});
g.FillPolygon(new SolidBrush(m_lineColor), new Point[] {new Point(hoverItem.Bounds.X + hoverItem.Bounds.Width - 5, hoverItem.Bounds.Y + hoverItem.Bounds.Height), new Point(hoverItem.Bounds.X + hoverItem.Bounds.Width + 5, hoverItem.Bounds.Y + hoverItem.Bounds.Height), new Point(hoverItem.Bounds.X + hoverItem.Bounds.Width, hoverItem.Bounds.Y + hoverItem.Bounds.Height - 5)});
}

// call the base OnDragOver event
base.OnDragOver(drgevent);

return;
}

// determine if the user is currently hovering over a new
// item. If so, set the previous item's back color back
// to the default color.
if((m_previousItem != null && m_previousItem != hoverItem) || m_previousItem == null)
{
this.Invalidate();
}

// set the background color of the item being hovered
// and assign the previous item to the item being hovered
//hoverItem.BackColor = Color.Beige;
m_previousItem = hoverItem;

if(this.View == View.Details || this.View == View.List)
{
g.DrawLine(new Pen(m_lineColor, 2), new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y), new Point(hoverItem.Bounds.X + this.Bounds.Width, hoverItem.Bounds.Y));
g.FillPolygon(new SolidBrush(m_lineColor), new Point[] {new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y - 5), new Point(hoverItem.Bounds.X + 5, hoverItem.Bounds.Y), new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + 5)});
g.FillPolygon(new SolidBrush(m_lineColor), new Point[] {new Point(this.Bounds.Width - 4, hoverItem.Bounds.Y - 5), new Point(this.Bounds.Width - 9, hoverItem.Bounds.Y), new Point(this.Bounds.Width - 4, hoverItem.Bounds.Y + 5)});
}
else
{
g.DrawLine(new Pen(m_lineColor, 2), new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y), new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + hoverItem.Bounds.Height));
g.FillPolygon(new SolidBrush(m_lineColor), new Point[] {new Point(hoverItem.Bounds.X - 5, hoverItem.Bounds.Y), new Point(hoverItem.Bounds.X + 5, hoverItem.Bounds.Y), new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + 5)});
g.FillPolygon(new SolidBrush(m_lineColor), new Point[] {new Point(hoverItem.Bounds.X - 5, hoverItem.Bounds.Y + hoverItem.Bounds.Height), new Point(hoverItem.Bounds.X + 5, hoverItem.Bounds.Y + hoverItem.Bounds.Height), new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + hoverItem.Bounds.Height - 5)});
}

// go through each of the selected items, and if any of the
// selected items have the same index as the item being
// hovered, disable dropping.
foreach(ListViewItem itemToMove in base.SelectedItems)
{
if(itemToMove.Index == hoverItem.Index)
{
drgevent.Effect = DragDropEffects.None;
hoverItem.EnsureVisible();
return;
}
}

// ensure that the hover item is visible
hoverItem.EnsureVisible();
}

// everything is fine, allow the user to move the items
drgevent.Effect = DragDropEffects.Move;

// call the base OnDragOver event
base.OnDragOver(drgevent);
}

protected override void OnDragEnter(DragEventArgs drgevent)
{
if(!m_allowReorder)
{
base.OnDragEnter(drgevent);
return;
}

if(!drgevent.Data.GetDataPresent(typeof(DragItemData).ToString()))
{
// the item(s) being dragged do not have any data associated
drgevent.Effect = DragDropEffects.None;
return;
}

// everything is fine, allow the user to move the items
drgevent.Effect = DragDropEffects.Move;

// call the base OnDragEnter event
base.OnDragEnter(drgevent);
}

protected override void OnItemDrag(ItemDragEventArgs e)
{
if(!m_allowReorder)
{
base.OnItemDrag(e);
return;
}

// call the DoDragDrop method
base.DoDragDrop(GetDataForDragDrop(), DragDropEffects.Move);

// call the base OnItemDrag event
base.OnItemDrag(e);
}

protected override void OnLostFocus(EventArgs e)
{
// reset the selected items background and remove the previous item
ResetOutOfRange();

Invalidate();

// call the OnLostFocus event
base.OnLostFocus(e);
}

protected override void OnDragLeave(EventArgs e)
{
// reset the selected items background and remove the previous item
ResetOutOfRange();

Invalidate();

// call the base OnDragLeave event
base.OnDragLeave(e);
}

#endregion

#region Private Methods

private DragItemData GetDataForDragDrop()
{
// create a drag item data object that will be used to pass along with the drag and drop
DragItemData data = new DragItemData(this);

// go through each of the selected items and
// add them to the drag items collection
// by creating a clone of the list item
foreach(ListViewItem item in this.SelectedItems)
{
ListViewItem newItem = (ListViewItem)item.Clone();
newItem.Name = item.Name;
data.DragItems.Add(newItem);
}

return data;
}

private void ResetOutOfRange()
{
// determine if the previous item exists,
// if it does, reset the background and release
// the previous item
if(m_previousItem != null)
{
m_previousItem = null;
}

}

#endregion

#region DragItemData Class

private class DragItemData
{
#region Private Members

private DragAndDropListView m_listView;
private ArrayList m_dragItems;

#endregion

#region Public Properties

public DragAndDropListView ListView
{
get { return m_listView; }
}

public ArrayList DragItems
{
get { return m_dragItems; }
}

#endregion

#region Public Methods and Implementation

public DragItemData(DragAndDropListView listView)
{
m_listView = listView;
m_dragItems = new ArrayList();
}

#endregion
}

#endregion
}
}

"Jumping" at the bottom on drag and drop [FIX] - dragging down 2 nodes instead of one [FIX]

paintor

2:37 11 Feb '08

I was recieving a jumping of the selector when dragging downward. This appeared to be related to the dragging over the horizontal scrollbar. I fixed this by detecting if the jump should be applied or not (not tested for multiple listviews)

private const int WS_HSCROLL = 0x100000;
private const int GWL_STYLE = (-16);

[DllImport("user32", CharSet=CharSet.Auto)]
private static extern int GetWindowLong(IntPtr hwnd, int nIndex);

private bool IsHorizontalScrollBarVisible()
{
if (!this.IsHandleCreated)
return false;

return (GetWindowLong(this.Handle, GWL_STYLE) & WS_HSCROLL) != 0;
}

will detect if the scrollbar is present, and in OnDragOver() before the call to CreateGraphics

if( hoverItem == null )
{
if ( IsHorizontalScrollBarVisible() )
{
// added 2 px to scrollbar to avoid jump in gutter
hoverItem = base.GetItemAt(clientPoint.X, clientPoint.Y -
SystemInformation.HorizontalScrollBarHeight + 2 );
if( hoverItem != null )
{
if ( hoverItem.Index == this.Items.Count - 1 )
{
// found the last one, we want to drop at the bottom
hoverItem = null;
}
else
{
this.EnsureVisible( hoverItem.Index + 1 );
}
}
}
}

This works for horizontal scrollbar visible or not, with arbritrary vertical scrollbar.

Additionally I found the dragging down counter intuitive as it dropped an item 2 nodes below instead of "in the middle" where the selector was (due to the line being at the top of each node). I therefore took out the code below from OnDragDrop()

// determine if the items to be dropped are from
// this list view. If they are, perform a hack
// to increment the hover index so that the items
// get moved properly.

// if(this == data.ListView)
// {
// if(hoverIndex > base.SelectedItems[0].Index)
// hoverIndex++;
//}

Please note these alterations are not tested on multiple list boxes

Problem with Sorting [modified]

shashank_156

0:31 11 Feb '08

Hi

Thanks for creating such an useful control.

I have come across a serious problem while using it.

it works fine until the sorting property is set to none.but when i change it to ascending or descending,the drag and drop WITHIN the same listview does not work.
i works fine if i drag an item from one list view and drop it to another.

Anyone has the solution ? pls reply

modified on Monday, February 11, 2008 6:09 AM

5.00/5

Bug Fix - When reordering down and horizontal scroll bar is visible

Steve Marshall

7:25 29 Oct '07

When the horizontal scroll bar is visible and the display rectangle for the listview is a couple of pixles smaller than N complete items, you cannot drag an item down the list...

To fix this you need to add an extra if statement to the OnDragOver() method. Add the following after the call to GetItemAt(clientPoint.X, clientPoint.Y) but before CreateGraphics().

<code>
// If we are trying to scroll down, we might be stuck on the horizontal scroll bar, get the
// item and scroll the next item into view.
if( hoverItem == null )
{
   hoverItem = base.GetItemAt(clientPoint.X, clientPoint.Y - SystemInformation.HorizontalScrollBarHeight );
   if( hoverItem != null )
   {
         this.EnsureVisible( hoverItem.Index + 1 );
   }
}
</code>

VB Code

powermetal

9:19 1 Oct '07

It took me to convert to VB about 3hs+, I'm newbie and think that this can help someone (I used some tools to convert the code but none of those work well, then I manually translate the code...)

Imports System
Imports System.Drawing
Imports System.Collections
Imports System.Windows.Forms
Imports System.ComponentModel

namespace DragNDrop

Public Class DragAndDropListView
    Inherits ListView

#Region "Private Members"
    Private m_previousItem As ListViewItem
    Private m_allowReorder As Boolean
    Private m_lineColor As Color
#End Region

#Region "Public Properties"

    "Behavior")> _
    Public Property AllowReorder() As Boolean
        Get
            Return m_allowReorder
        End Get
        Set(ByVal value As Boolean)
            m_allowReorder = value
        End Set
    End Property

    "Appearance")> _
    Public Property LineColor() As Color
        Get
            Return m_lineColor
        End Get
        Set(ByVal value As Color)
            m_lineColor = value
        End Set
    End Property
#End Region

#Region "Protected and Public Methods"
    Public Sub New()
        MyBase.New()
        m_allowReorder = True
        m_lineColor = Color.Red

        'Me.FullRowSelect = False
    End Sub

    Protected Overrides Sub OnDragDrop(ByVal drgevent As DragEventArgs)
        If Not m_allowReorder Then
            MyBase.OnDragDrop(drgevent)
            Return
        End If

        ' get the currently hovered row that the items will be dragged to
        Dim clientPoint As Point = MyBase.PointToClient(New Point(drgevent.X, drgevent.Y))
        Dim hoverItem As ListViewItem = MyBase.GetItemAt(clientPoint.X, clientPoint.Y)

        If Not drgevent.Data.GetDataPresent(GetType(DragItemData).ToString()) OrElse _
            (CType(drgevent.Data.GetData(GetType(DragItemData).ToString()), DragItemData)).ListView Is Nothing OrElse _
            (CType(drgevent.Data.GetData(GetType(DragItemData).ToString()), DragItemData)).DragItems.Count = 0 Then Return

        'retrieve the drag item data
        Dim data As DragItemData = CType(drgevent.Data.GetData(GetType(DragItemData).ToString()), DragItemData)

        If hoverItem Is Nothing Then
            'the user does not wish to re-order the items, just append to the end
            For i As Integer = 0 To data.DragItems.Count - 1
                Dim newItem As ListViewItem = CType(data.DragItems(i), ListViewItem)
                MyBase.Items.Add(newItem)
            Next
        Else
            ' the user wishes to re-order the items

            ' get the index of the hover item
            Dim hoverIndex As Integer = hoverItem.Index

            ' determine if the items to be dropped are from
            ' this list view. If they are, perform a hack
            ' to increment the hover index so that the items
            ' get moved properly.
            If Me Is data.ListView Then
                If hoverIndex > MyBase.SelectedItems(0).Index Then
                    hoverIndex += 1
                End If
            End If
            ' insert the new items into the list view
            ' by inserting the items reversely from the array list
            For i As Integer = data.DragItems.Count - 1 To 0 Step -1
                Dim newItem As ListViewItem = CType(data.DragItems(i), ListViewItem)
                MyBase.Items.Insert(hoverIndex, newItem)
            Next
        End If

        ' remove all the selected items from the previous list view
        ' if the list view was found
        If data.ListView IsNot Nothing Then
            For Each itemToRemove As ListViewItem In data.ListView.SelectedItems
                data.ListView.Items.Remove(itemToRemove)
            Next
        End If

        ' set the back color of the previous item, then nullify it
        If m_previousItem IsNot Nothing Then
            m_previousItem = Nothing
        End If

        Me.Invalidate()

        ' call the base on drag drop to raise the event
        MyBase.OnDragDrop(drgevent)
    End Sub

    Protected Overrides Sub OnDragOver(ByVal drgevent As DragEventArgs)
        If Not m_allowReorder Then
            MyBase.OnDragOver(drgevent)
            Return
        End If

        If Not drgevent.Data.GetDataPresent(GetType(DragItemData).ToString()) Then
            ' the item(s) being dragged do not have any data associated
            drgevent.Effect = DragDropEffects.None
            Return
        End If

        If MyBase.Items.Count > 0 Then
            ' get the currently hovered row that the items will be dragged to
            Dim clientPoint As Point = MyBase.PointToClient(New Point(drgevent.X, drgevent.Y))
            Dim hoverItem As ListViewItem = MyBase.GetItemAt(clientPoint.X, clientPoint.Y)

            Dim g As Graphics = Me.CreateGraphics()

            If hoverItem Is Nothing Then

                'MessageBox.Show(base.GetChildAtPoint(new Point(clientPoint.X, clientPoint.Y)).GetType().ToString());

                ' no item was found, so no drop should take place
                drgevent.Effect = DragDropEffects.Move

                If m_previousItem IsNot Nothing Then
                    m_previousItem = Nothing
                    Invalidate()
                End If

                hoverItem = MyBase.Items(MyBase.Items.Count - 1)

                If Me.View = View.Details OrElse Me.View = View.List Then
                    g.DrawLine(New Pen(m_lineColor, 2), New Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + hoverItem.Bounds.Height), New Point(hoverItem.Bounds.X + Me.Bounds.Width, hoverItem.Bounds.Y + hoverItem.Bounds.Height))
                    g.FillPolygon(New SolidBrush(m_lineColor), New Point() {New Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + hoverItem.Bounds.Height - 5), New Point(hoverItem.Bounds.X + 5, hoverItem.Bounds.Y + hoverItem.Bounds.Height), New Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + hoverItem.Bounds.Height + 5)})
                    g.FillPolygon(New SolidBrush(m_lineColor), New Point() {New Point(Me.Bounds.Width - 4, hoverItem.Bounds.Y + hoverItem.Bounds.Height - 5), New Point(Me.Bounds.Width - 9, hoverItem.Bounds.Y + hoverItem.Bounds.Height), New Point(Me.Bounds.Width - 4, hoverItem.Bounds.Y + hoverItem.Bounds.Height + 5)})
                Else
                    g.DrawLine(New Pen(m_lineColor, 2), New Point(hoverItem.Bounds.X + hoverItem.Bounds.Width, hoverItem.Bounds.Y), New Point(hoverItem.Bounds.X + hoverItem.Bounds.Width, hoverItem.Bounds.Y + hoverItem.Bounds.Height))
                    g.FillPolygon(New SolidBrush(m_lineColor), New Point() {New Point(hoverItem.Bounds.X + hoverItem.Bounds.Width - 5, hoverItem.Bounds.Y), New Point(hoverItem.Bounds.X + hoverItem.Bounds.Width + 5, hoverItem.Bounds.Y), New Point(hoverItem.Bounds.X + hoverItem.Bounds.Width, hoverItem.Bounds.Y + 5)})
                    g.FillPolygon(New SolidBrush(m_lineColor), New Point() {New Point(hoverItem.Bounds.X + hoverItem.Bounds.Width - 5, hoverItem.Bounds.Y + hoverItem.Bounds.Height), New Point(hoverItem.Bounds.X + hoverItem.Bounds.Width + 5, hoverItem.Bounds.Y + hoverItem.Bounds.Height), New Point(hoverItem.Bounds.X + hoverItem.Bounds.Width, hoverItem.Bounds.Y + hoverItem.Bounds.Height - 5)})
                End If

                ' call the base OnDragOver event
                MyBase.OnDragOver(drgevent)

                Return
            End If

            ' determine if the user is currently hovering over a new
            ' item. If so, set the previous item's back color back
            ' to the default color.
            If (m_previousItem IsNot Nothing AndAlso m_previousItem IsNot hoverItem) OrElse m_previousItem Is Nothing Then
                Me.Invalidate()
            End If

            ' set the background color of the item being hovered
            ' and assign the previous item to the item being hovered
            'hoverItem.BackColor = Color.Beige;
            m_previousItem = hoverItem

            If Me.View = View.Details OrElse Me.View = View.List Then
                g.DrawLine(New Pen(m_lineColor, 2), New Point(hoverItem.Bounds.X, hoverItem.Bounds.Y), New Point(hoverItem.Bounds.X + Me.Bounds.Width, hoverItem.Bounds.Y))
                g.FillPolygon(New SolidBrush(m_lineColor), New Point() {New Point(hoverItem.Bounds.X, hoverItem.Bounds.Y - 5), New Point(hoverItem.Bounds.X + 5, hoverItem.Bounds.Y), New Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + 5)})
                g.FillPolygon(New SolidBrush(m_lineColor), New Point() {New Point(Me.Bounds.Width - 4, hoverItem.Bounds.Y - 5), New Point(Me.Bounds.Width - 9, hoverItem.Bounds.Y), New Point(Me.Bounds.Width - 4, hoverItem.Bounds.Y + 5)})
            Else
                g.DrawLine(New Pen(m_lineColor, 2), New Point(hoverItem.Bounds.X, hoverItem.Bounds.Y), New Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + hoverItem.Bounds.Height))
                g.FillPolygon(New SolidBrush(m_lineColor), New Point() {New Point(hoverItem.Bounds.X - 5, hoverItem.Bounds.Y), New Point(hoverItem.Bounds.X + 5, hoverItem.Bounds.Y), New Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + 5)})
                g.FillPolygon(New SolidBrush(m_lineColor), New Point() {New Point(hoverItem.Bounds.X - 5, hoverItem.Bounds.Y + hoverItem.Bounds.Height), New Point(hoverItem.Bounds.X + 5, hoverItem.Bounds.Y + hoverItem.Bounds.Height), New Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + hoverItem.Bounds.Height - 5)})
                ' go through each of the selected items, and if any of the
                ' selected items have the same index as the item being
                ' hovered, disable dropping.

                For Each itemToMove As ListViewItem In MyBase.SelectedItems
                    If itemToMove.Index = hoverItem.Index Then
                        drgevent.Effect = DragDropEffects.None
                        hoverItem.EnsureVisible()
                        Return
                    End If
                Next
            End If
            ' ensure that the hover item is visible
            hoverItem.EnsureVisible()
        End If

        ' everything is fine, allow the user to move the items
        drgevent.Effect = DragDropEffects.Move

        ' call the base OnDragOver event
        MyBase.OnDragOver(drgevent)
    End Sub

    Protected Overrides Sub OnDragEnter(ByVal drgevent As DragEventArgs)
        If Not m_allowReorder Then
            MyBase.OnDragEnter(drgevent)
            Return
        End If

        If Not drgevent.Data.GetDataPresent(GetType(DragItemData).ToString()) Then
            ' the item(s) being dragged do not have any data associated
            drgevent.Effect = DragDropEffects.None
            Return

        End If

        ' everything is fine, allow the user to move the items
        drgevent.Effect = DragDropEffects.Move

        ' call the base OnDragEnter event
        MyBase.OnDragEnter(drgevent)

    End Sub

    Protected Overrides Sub OnItemDrag(ByVal e As ItemDragEventArgs)
        If Not m_allowReorder Then
            MyBase.OnItemDrag(e)
            Return
        End If

        ' call the DoDragDrop method
        MyBase.DoDragDrop(GetDataForDragDrop(), DragDropEffects.Move)

        ' call the base OnItemDrag event
        MyBase.OnItemDrag(e)
    End Sub

    Protected Overrides Sub OnLostFocus(ByVal e As EventArgs)
        ' reset the selected items background and remove the previous item
        ResetOutOfRange()

        Invalidate()

        ' call the OnLostFocus event
        MyBase.OnLostFocus(e)
    End Sub

    Protected Overrides Sub OnDragLeave(ByVal e As EventArgs)
        ' reset the selected items background and remove the previous item
        ResetOutOfRange()

        Invalidate()

        ' call the base OnDragLeave event
        MyBase.OnDragLeave(e)
    End Sub

#Region "Private Methods"
    Private Function GetDataForDragDrop() As DragItemData
        ' create a drag item data object that will be used to pass along with the drag and drop
        Dim data As DragItemData = New DragItemData(Me)

        ' go through each of the selected items and 
        ' add them to the drag items collection
        ' by creating a clone of the list item

        For Each item As ListViewItem In Me.SelectedItems
            data.DragItems.Add(item.Clone())
        Next

        Return data
    End Function

    Private Sub ResetOutOfRange()
        ' determine if the previous item exists,
        ' if it does, reset the background and release 
        ' the previous item
        If m_previousItem IsNot Nothing Then
            m_previousItem = Nothing
        End If
    End Sub

#End Region


#End Region

#Region "DragItemData Class"
    Private Class DragItemData

#Region "Private Members"
        Private m_listView As DragAndDropListView
        Private m_dragItems As ArrayList
#End Region

#Region "Public Properties"

        Public ReadOnly Property ListView() As DragAndDropListView
            Get
                Return m_listView
            End Get
        End Property

        Public ReadOnly Property DragItems() As ArrayList
            Get
                Return m_dragItems
            End Get
        End Property

#End Region

#Region "Public Methods and Implementation"
        Public Sub New(ByVal listView As DragAndDropListView)
            m_listView = listView
            m_dragItems = New ArrayList()
        End Sub
#End Region

    End Class
#End Region

End Class

END NAMESPACE

Bug Fix for LargeIcon or SmallIcon view

huanyi

4:02 25 Sep '07

It works very well but in LargeIcon or SmallIcon
I do some fix in DragAndDropListView.cs as below

using System;
using System.Drawing;
using System.Collections;
using System.Windows.Forms;
using System.ComponentModel;

namespace DragNDrop
{
    public class DragAndDropListView : ListView
    {
        #region Private Members

        private ListViewItem m_previousItem;
        private bool m_allowReorder;
        private Color m_lineColor;

        #endregion

        #region Public Properties

        [Category("Behavior")]
        public bool AllowReorder
        {
            get { return m_allowReorder; }
            set { m_allowReorder = value; }
        }

        [Category("Appearance")]
        public Color LineColor
        {
            get { return m_lineColor; }
            set { m_lineColor = value; }
        }

        #endregion

        #region Protected and Public Methods

        public DragAndDropListView()
            : base()
        {
            m_allowReorder = true;
            m_lineColor = Color.Black;
        }

        protected override void OnDragDrop(DragEventArgs drgevent)
        {
            if (!m_allowReorder)
            {
                base.OnDragDrop(drgevent);
                return;
            }

            // get the currently hovered row that the items will be dragged to
            Point clientPoint = base.PointToClient(new Point(drgevent.X, drgevent.Y));
            ListViewItem hoverItem = base.GetItemAt(clientPoint.X, clientPoint.Y);

            if (!drgevent.Data.GetDataPresent(typeof(DragItemData).ToString()) || ((DragItemData)drgevent.Data.GetData(typeof(DragItemData).ToString())).ListView == null || ((DragItemData)drgevent.Data.GetData(typeof(DragItemData).ToString())).DragItems.Count == 0)
                return;

            // retrieve the drag item data
            DragItemData data = (DragItemData)drgevent.Data.GetData(typeof(DragItemData).ToString());

            if (hoverItem == null)
            {
                // the user does not wish to re-order the items, just append to the end
                for (int i = 0; i < data.DragItems.Count; i++)
                {
                    ListViewItem newItem = (ListViewItem)data.DragItems[i];
                    base.Items.Add(newItem);
                }
            }
            else
            {
                // the user wishes to re-order the items

                // get the index of the hover item
                int hoverIndex = hoverItem.Index;

                // determine if the items to be dropped are from
                // this list view. If they are, perform a hack
                // to increment the hover index so that the items
                // get moved properly.
                if (this == data.ListView)
                {
                    if (base.SelectedItems[0].Index <= hoverIndex && hoverIndex <= base.SelectedItems[base.SelectedItems.Count - 1].Index + 1)
                    {
                        if (m_previousItem != null)
                        {
                            m_previousItem = null;
                        }

                        this.Invalidate();

                        // call the base on drag drop to raise the event
                        base.OnDragDrop(drgevent);
                        return;
                    }
                    //else if (hoverIndex > base.SelectedItems[0].Index)
                    //    hoverIndex += base.SelectedItems.Count;
                }

                // insert the new items into the list view
                // by inserting the items reversely from the array list
                for (int i = data.DragItems.Count - 1; i >= 0; i--)
                {
                    ListViewItem newItem = (ListViewItem)data.DragItems[i];
                    base.Items.Insert(hoverIndex, newItem);
                    base.Items[hoverIndex].Position = base.Items[hoverIndex + 1].Position;
                }
            }

            // remove all the selected items from the previous list view
            // if the list view was found
            if (data.ListView != null)
            {
                foreach (ListViewItem itemToRemove in data.ListView.SelectedItems)
                {
                    data.ListView.Items.Remove(itemToRemove);
                }
            }
            //this.ArrangeIcons();
            //this.
            //this.Sorting = SortOrder.Ascending;
            //this.Sort();

            //base.AutoArrange = true;
            //base.Refresh();
            //this.ArrangeIcons();
            this.Refresh();
            //this.ArrangeIcons();
            //this.RedrawItems(0, base.Items.Count - 1, false);
            // set the back color of the previous item, then nullify it
            if (m_previousItem != null)
            {
                m_previousItem = null;
            }

            this.Invalidate();

            // call the base on drag drop to raise the event
            base.OnDragDrop(drgevent);
        }

        protected override void OnDragOver(DragEventArgs drgevent)
        {
            if (!m_allowReorder)
            {
                base.OnDragOver(drgevent);
                return;
            }

            if (!drgevent.Data.GetDataPresent(typeof(DragItemData).ToString()))
            {
                // the item(s) being dragged do not have any data associated
                drgevent.Effect = DragDropEffects.None;
                return;
            }

            if (base.Items.Count > 0)
            {
                // get the currently hovered row that the items will be dragged to
                Point clientPoint = base.PointToClient(new Point(drgevent.X, drgevent.Y));
                ListViewItem lastItem = base.Items[base.Items.Count - 1];
                Point ptLastItem = new Point(lastItem.Bounds.X + lastItem.Bounds.Width + lastItem.Bounds.X, lastItem.Bounds.Y + lastItem.Bounds.Height);
                ListViewItem hoverItem = base.GetItemAt(clientPoint.X, clientPoint.Y);

                Graphics g = this.CreateGraphics();

                if (hoverItem == null && (clientPoint.X > ptLastItem.X || clientPoint.Y > ptLastItem.Y))
                {
                    //MessageBox.Show(base.GetChildAtPoint(new Point(clientPoint.X, clientPoint.Y)).GetType().ToString());

                    // no item was found, so no drop should take place
                    drgevent.Effect = DragDropEffects.Move;

                    if (m_previousItem != null)
                    {
                        m_previousItem = null;
                        Invalidate();
                    }

                    hoverItem = base.Items[base.Items.Count - 1];

                    if (this.View == View.Details || this.View == View.List)
                    {
                        g.DrawLine(new Pen(m_lineColor, 2), new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + hoverItem.Bounds.Height), new Point(hoverItem.Bounds.X + this.Bounds.Width, hoverItem.Bounds.Y + hoverItem.Bounds.Height));
                        //g.FillPolygon(new SolidBrush(m_lineColor), new Point[] {new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + hoverItem.Bounds.Height - 5), new Point(hoverItem.Bounds.X + 5, hoverItem.Bounds.Y + hoverItem.Bounds.Height), new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + hoverItem.Bounds.Height + 5)});
                        //g.FillPolygon(new SolidBrush(m_lineColor), new Point[] {new Point(this.Bounds.Width - 4, hoverItem.Bounds.Y + hoverItem.Bounds.Height - 5), new Point(this.Bounds.Width - 9, hoverItem.Bounds.Y + hoverItem.Bounds.Height), new Point(this.Bounds.Width - 4, hoverItem.Bounds.Y + hoverItem.Bounds.Height + 5)});
                    }
                    else
                    {
                        g.DrawLine(new Pen(m_lineColor, 2), new Point(hoverItem.Bounds.X + hoverItem.Bounds.Width, hoverItem.Bounds.Y), new Point(hoverItem.Bounds.X + hoverItem.Bounds.Width, hoverItem.Bounds.Y + hoverItem.Bounds.Height));
                        g.FillPolygon(new SolidBrush(m_lineColor), new Point[] { new Point(hoverItem.Bounds.X + hoverItem.Bounds.Width - 3, hoverItem.Bounds.Y), new Point(hoverItem.Bounds.X + hoverItem.Bounds.Width + 3, hoverItem.Bounds.Y), new Point(hoverItem.Bounds.X + hoverItem.Bounds.Width, hoverItem.Bounds.Y + 3) });
                        g.FillPolygon(new SolidBrush(m_lineColor), new Point[] { new Point(hoverItem.Bounds.X + hoverItem.Bounds.Width - 4, hoverItem.Bounds.Y + hoverItem.Bounds.Height), new Point(hoverItem.Bounds.X + hoverItem.Bounds.Width + 4, hoverItem.Bounds.Y + hoverItem.Bounds.Height), new Point(hoverItem.Bounds.X + hoverItem.Bounds.Width, hoverItem.Bounds.Y + hoverItem.Bounds.Height - 4) });
                    }

                    // call the base OnDragOver event
                    base.OnDragOver(drgevent);

                    return;
                }

                // determine if the user is currently hovering over a new
                // item. If so, set the previous item's back color back
                // to the default color.
                if ((m_previousItem != null && m_previousItem != hoverItem) || m_previousItem == null)
                {
                    this.Invalidate();
                }

                // set the background color of the item being hovered
                // and assign the previous item to the item being hovered
                //hoverItem.BackColor = Color.Beige;
                m_previousItem = hoverItem;

                if (this.View == View.Details || this.View == View.List)
                {
                    g.DrawLine(new Pen(m_lineColor, 2), new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y/* + hoverItem.Bounds.Height*/), new Point(hoverItem.Bounds.X + this.Bounds.Width, hoverItem.Bounds.Y /*+ 2 *hoverItem.Bounds.Height*/));
                    //g.FillPolygon(new SolidBrush(m_lineColor), new Point[] { new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y - 3 + hoverItem.Bounds.Height), new Point(hoverItem.Bounds.X + 3, hoverItem.Bounds.Y + hoverItem.Bounds.Height), new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + 3 + hoverItem.Bounds.Height) });
                    //g.FillPolygon(new SolidBrush(m_lineColor), new Point[] { new Point(this.Bounds.Width - 4, hoverItem.Bounds.Y - 4 + hoverItem.Bounds.Height), new Point(this.Bounds.Width - 9, hoverItem.Bounds.Y + hoverItem.Bounds.Height -1 ), new Point(this.Bounds.Width - 4, hoverItem.Bounds.Y + 3 + hoverItem.Bounds.Height -1) });
                }
                else
                {
                    g.DrawLine(new Pen(m_lineColor, 2), new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y), new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + hoverItem.Bounds.Height));
                    g.FillPolygon(new SolidBrush(m_lineColor), new Point[] { new Point(hoverItem.Bounds.X - 3, hoverItem.Bounds.Y), new Point(hoverItem.Bounds.X + 3, hoverItem.Bounds.Y), new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + 3) });
                    g.FillPolygon(new SolidBrush(m_lineColor), new Point[] { new Point(hoverItem.Bounds.X - 4, hoverItem.Bounds.Y + hoverItem.Bounds.Height), new Point(hoverItem.Bounds.X + 4, hoverItem.Bounds.Y + hoverItem.Bounds.Height), new Point(hoverItem.Bounds.X, hoverItem.Bounds.Y + hoverItem.Bounds.Height - 4) });
                }

                // go through each of the selected items, and if any of the
                // selected items have the same index as the item being
                // hovered, disable dropping.
                foreach (ListViewItem itemToMove in base.SelectedItems)
                {
                    if (itemToMove.Index == hoverItem.Index)
                    {
                        drgevent.Effect = DragDropEffects.None;
                        hoverItem.EnsureVisible();
                        return;
                    }
                }

                // ensure that the hover item is visible
                hoverItem.EnsureVisible();
            }

            // everything is fine, allow the user to move the items
            drgevent.Effect = DragDropEffects.Move;

            // call the base OnDragOver event
            base.OnDragOver(drgevent);
        }

        protected override void OnDragEnter(DragEventArgs drgevent)
        {
            if (!m_allowReorder)
            {
                base.OnDragEnter(drgevent);
                return;
            }

            if (!drgevent.Data.GetDataPresent(typeof(DragItemData).ToString()))
            {
                // the item(s) being dragged do not have any data associated
                drgevent.Effect = DragDropEffects.None;
                return;
            }

            // everything is fine, allow the user to move the items
            drgevent.Effect = DragDropEffects.Move;

            // call the base OnDragEnter event
            base.OnDragEnter(drgevent);
        }

        protected override void OnItemDrag(ItemDragEventArgs e)
        {
            if (!m_allowReorder)
            {
                base.OnItemDrag(e);
                return;
            }

            // call the DoDragDrop method
            base.DoDragDrop(GetDataForDragDrop(), DragDropEffects.Move);

            // call the base OnItemDrag event
            base.OnItemDrag(e);
        }

        protected override void OnLostFocus(EventArgs e)
        {
            // reset the selected items background and remove the previous item
            ResetOutOfRange();

            Invalidate();

            // call the OnLostFocus event
            base.OnLostFocus(e);
        }

        protected override void OnDragLeave(EventArgs e)
        {
            // reset the selected items background and remove the previous item
            ResetOutOfRange();

            Invalidate();

            // call the base OnDragLeave event
            base.OnDragLeave(e);
        }

        #endregion

        #region Private Methods

        private DragItemData GetDataForDragDrop()
        {
            // create a drag item data object that will be used to pass along with the drag and drop
            DragItemData data = new DragItemData(this);

            // go through each of the selected items and 
            // add them to the drag items collection
            // by creating a clone of the list item
            foreach (ListViewItem item in this.SelectedItems)
            {
                data.DragItems.Add(item.Clone());
            }

            return data;
        }

        private void ResetOutOfRange()
        {
            // determine if the previous item exists,
            // if it does, reset the background and release 
            // the previous item
            if (m_previousItem != null)
            {
                m_previousItem = null;
            }

        }

        #endregion

        #region DragItemData Class

        private class DragItemData
        {
            #region Private Members

            private DragAndDropListView m_listView;
            private ArrayList m_dragItems;

            #endregion

            #region Public Properties

            public DragAndDropListView ListView
            {
                get { return m_listView; }
            }

            public ArrayList DragItems
            {
                get { return m_dragItems; }
            }

            #endregion

            #region Public Methods and Implementation

            public DragItemData(DragAndDropListView listView)
            {
                m_listView = listView;
                m_dragItems = new ArrayList();
            }

            #endregion
        }

        #endregion

        private void InitializeComponent()
        {
            this.SuspendLayout();
            this.ResumeLayout(false);

        }
    }
}

Re: Bug Fix for LargeIcon or SmallIcon view

nullesc

18:24 19 Nov '08

Thank you so much for the fix. The control was not working until I switched to this code with large icons. Without this fix the large Icon I was dragging would always move to the bottom.
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Drag&Drop only inside of current List

MichaZ123

1:30 8 Aug '07

Hello!

I am newbie to C#.

The problem is:

I have two Drag and Drop List Views in my form.

1.Dragging and dropping from one list to another should not be allowed.I mean,I should only allow dragging and dropping for List1 elements only in List1. How to do this?

2.Can I dinamically change the List element attributes when the dragged list element is dropped? How to do this?

3.How to sort the List by one element attribute? Currently I am working with XML. So I fetch the data from XML into a List, perform sorting by writing own comparer and only after then load the Drag And Drop List View with sorted data. Maybe there is an easier way?

3.How to retrieve current Drag And Drop List View with all elements in order how they are displayed.

Thanks Everyone!

Misha

1.00/5

Question

loneferret

13:02 17 Jul '06

Just let me say that I love your code. Good comments and easy to follow. Smile

Now for my question.
I would need to have one of the listviews to have 3rd column (which I can do) with permanent information in it. Such as row 1, row 2 etc.
So as when you drag a selection from one listview (the one with only 2 columns) to the other
(the one with the row count) the row count stays in the first column and the other two are inserted.
GOD, I hope i'm explaining myself correctly... lol I may be long-winded here, just want to make sure someone understands me...
So...
listview #1 has:
list1 | item 1

listview #2 has:
row 1 | |

When dragging from list 1 over to 2 it displays
row 1 | list1 | item1

Hope this is clear.. been busting my back-side over this, would really need some help on this one.
Really...
Thank you for any help..

LoneFerret

Cross my heart, smack me dead...stick a lobster on my head.

Licensing

mark_ledwich

20:44 20 Apr '06

This is a great control and its exactly what i need. Can I use it in comercial code(recognition will be given in the design document)?
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View LargeIcon ?

miha52

23:59 7 Nov '05

Hi, When I use your component, and if ListView.View = LargeIcon then item reorder - did not work. Any idea to solve this problem ?
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Flicker when dragging

dgannon34

19:16 16 Sep '05

This is exactly what I needed, thanks! Only problem I have is hideous flicker when dragging. I've tried a few different things, but with no success. Any ideas?
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how to implement drag and drop in the asp.net page ,like list data or multiple select from one to another

Jade_king

23:13 15 Sep '05

tks
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ListViewItem Image problem

didis

6:24 1 Dec '04

Hi, When I use your component, and if i have setup the image list property. The image appear on the left of the listviewitem ... and disappear after a drag&drop. Any idea to solve this problem ? Didier.
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Re: ListViewItem Image problem

Diego F.

5:30 3 Apr '07

I see that this thread is quite old. Any solution to the image problem? Regards, Diego F.
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Allow both items drag & drop and files drag & drop

Bertrand Dunogier

3:35 3 Oct '04

First, let me thank you for your control, it's quite amazing. Now my problem is that I'd still like to allow external files drag & dropping to one of my listviews, while still allowing items reordering. When I drag a file over my listview, the DragEnter even is not even called. If I disable AllowReorder, everything works fine. What can I do to enable both at the same time ? Thanks in advance.
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Re: Allow both items drag & drop and files drag & drop

Craig Nagy

19:37 1 Mar '05

For others who have this problem (I had it too). I just changed some of the logic. All drag and drop handlers should call the corresponding base events no matter what at some point in the code. Also, a drag drop should turn off column sorting just in case it's on so that reordering by dragging takes precedence over sorting. Cheers...
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Re: Allow both items drag & drop and files drag & drop

Chris Cocker

5:29 5 Apr '05

Craig, Can you show the code you changed for both these issues? TIA
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great control, 2 questions

cmac

3:41 24 Aug '04

1. you cant drag items from a standard listview, only from dragndrop control 2. it appears that the listview items when dragged down the listview, are added one extra line down, but when dragging up everything works fine.
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Re: great control, 2 questions

James Pepin

6:47 8 Jun '05

int hoverIndex = hoverItem.Index;

// determine if the items to be dropped are from
// this list view. If they are, perform a hack
// to (increment) decrement the hover index so that the items
// get moved properly.
if(this == data.ListView)
{
     if(hoverIndex > base.SelectedItems[0].Index)
          hoverIndex-= base.SelectedItems.Count;
}

this piece needs to be a decrement.   That fixes the problem of the selected items being placed too far down.

Another thing I added to it is down below this piece I've changed the order a bit.   Instead of first adding the listItems and then removing them from thier source list, I've removed them first, and then added them setting thier Selected Property to true, so that they stay selected when they are dropped.

I've only briefly looked at it, so if someone sees a reason why this would break it, please do tell.   This control is great by the way.

-J

2.00/5

Enhancement/bug fix for List/Details

Richard Birkby

0:17 23 Jul '04

In the OnDragOver event handler, the drawing of the horizontal line and triangles takes place.

When the scrollbar is displayed, the right hand triangle is drawn underneath the scrollbar. To correct this, you need to use ClientSize.Width, rather than the width of the hoverItem when drawing the line and triangle.

You can also use hoverItem.Bounds.Bottom rather than adding the Y+Height together - it makes the code a little simpler!

In addition, it's usually a good idea to Dispose of Brushes and Pens as soon as you've used them. This is easily done by wrapping them in a using() statement.

Apart from this - it's worked perfectly.
Thanks.

3.00/5

Thankyou

Richard Birkby

0:00 20 Jul '04

It works brilliantly. Thanks! One thing to remember - in case you are in the habit of subclassing ListItem and adding the subclass to the ListView (giving you a nice bit of polymorphism), you will need to override the Clone() method, cloning any data you store in the subclass. Also remember to provide a public, parameterless constructor to your subclass.
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Last Visit: 3:10 23 Nov '09 Last Update: 3:10 23 Nov '09

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