Manual Reordering of Items inside a ListView

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace ListViewCustomReorder
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();

            // Important:
            // Right now it's not possible to drag more than one LVItem, so make sure the LV is in single selection mode
            listView1.MultiSelect = false;
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            // Fill the LV with test values
            for (int i = 0; i < 20; i++)
            {
                ListViewItem it = new ListViewItem("Item " + i);
                it.SubItems.Add("Item " + i + "-1");
                it.SubItems.Add("Item " + i + "-2");
                it.SubItems.Add("Item " + i + "-3");
                listView1.Items.Add(it);
            }
        }

        // The LVItem being dragged
        private ListViewItem _itemDnD = null;
        
        private void listView1_MouseDown(object sender, MouseEventArgs e)
        {
            _itemDnD = listView1.GetItemAt(e.X, e.Y);
            // if the LV is still empty, no item will be found anyway, so we don't have to consider this case
        }

        private void listView1_MouseMove(object sender, MouseEventArgs e)
        {
            if (_itemDnD == null)
                return;

            // Show the user that a drag operation is happening
            Cursor = Cursors.Hand;

            // calculate the bottom of the last item in the LV so that you don't have to stop your drag at the last item
            int lastItemBottom = Math.Min(e.Y, listView1.Items[listView1.Items.Count-1].GetBounds(ItemBoundsPortion.Entire).Bottom-1);

            // use 0 instead of e.X so that you don't have to keep inside the columns while dragging
            ListViewItem itemOver = listView1.GetItemAt(0, lastItemBottom);

            if (itemOver == null)
                return;

            Rectangle rc = itemOver.GetBounds(ItemBoundsPortion.Entire);
            if (e.Y < rc.Top + (rc.Height / 2))
            {
                listView1.LineBefore = itemOver.Index;
                listView1.LineAfter = -1;
            }
            else
            {
                listView1.LineBefore = -1;
                listView1.LineAfter = itemOver.Index;
            }

            // invalidate the LV so that the insertion line is shown
            listView1.Invalidate();
        }

        private void listView1_MouseUp(object sender, MouseEventArgs e)
        {
            if (_itemDnD == null)
                return;

            try
            {
                // calculate the bottom of the last item in the LV so that you don't have to stop your drag at the last item
                int lastItemBottom = Math.Min(e.Y, listView1.Items[listView1.Items.Count - 1].GetBounds(ItemBoundsPortion.Entire).Bottom - 1);

                // use 0 instead of e.X so that you don't have to keep inside the columns while dragging
                ListViewItem itemOver = listView1.GetItemAt(0, lastItemBottom);

                if (itemOver == null)
                    return;

                Rectangle rc = itemOver.GetBounds(ItemBoundsPortion.Entire);

                // find out if we insert before or after the item the mouse is over
                bool insertBefore;
                if (e.Y < rc.Top + (rc.Height / 2))
                {
                    insertBefore = true;
                }
                else
                {
                    insertBefore = false;
                }

                if (_itemDnD != itemOver) // if we dropped the item on itself, nothing is to be done
                {
                    if (insertBefore)
                    {
                        listView1.Items.Remove(_itemDnD);
                        listView1.Items.Insert(itemOver.Index, _itemDnD);
                    }
                    else
                    {
                        listView1.Items.Remove(_itemDnD);
                        listView1.Items.Insert(itemOver.Index + 1, _itemDnD);
                    }
                }

                // clear the insertion line
                listView1.LineAfter =
                listView1.LineBefore = -1;

                listView1.Invalidate();

            }
            finally
            {
                // finish drag&drop operation
                _itemDnD = null;
                Cursor = Cursors.Default;
            }
        }
    }
}