Question

I’d like to enable user to rearrange TabPages order by dragging and dropping. Moreover it’d be cool to enable user to drag TabPages from one TabControl to another. Both the way like in Firefox and Total Commander. How to achieve this?

Answer 1

reordering TabPages with drag and drop – by Ludwig B.

inspired by http://dotnetrix.co.uk/tabcontrol.htm#tip7

        private void tc_MouseDown(object sender, MouseEventArgs e)
        {
            // store clicked tab
            TabControl tc = (TabControl)sender;
            int hover_index = this.getHoverTabIndex(tc);
            if (hover_index >= 0) { tc.Tag = tc.TabPages[hover_index]; }
        }
        private void tc_MouseUp(object sender, MouseEventArgs e)
        {
            // clear stored tab
            TabControl tc = (TabControl)sender;
            tc.Tag = null;
        }
        private void tc_MouseMove(object sender, MouseEventArgs e)
        {           
            // mouse button down? tab was clicked?
            TabControl tc = (TabControl)sender;
            if ((e.Button != MouseButtons.Left) || (tc.Tag == null)) return;
            TabPage clickedTab = (TabPage)tc.Tag;
            int clicked_index = tc.TabPages.IndexOf(clickedTab);

            // start drag n drop
            tc.DoDragDrop(clickedTab, DragDropEffects.All);
        }
        private void tc_DragOver(object sender, DragEventArgs e)
        {
            TabControl tc = (TabControl)sender;

            // a tab is draged?
            if (e.Data.GetData(typeof(TabPage)) == null) return;
            TabPage dragTab = (TabPage)e.Data.GetData(typeof(TabPage));
            int dragTab_index = tc.TabPages.IndexOf(dragTab);

            // hover over a tab?
            int hoverTab_index = this.getHoverTabIndex(tc);
            if (hoverTab_index < 0) { e.Effect = DragDropEffects.None; return; }
            TabPage hoverTab = tc.TabPages[hoverTab_index];
            e.Effect = DragDropEffects.Move;

            // start of drag?
            if (dragTab == hoverTab) return;

            // swap dragTab & hoverTab - avoids toggeling
            Rectangle dragTabRect = tc.GetTabRect(dragTab_index);
            Rectangle hoverTabRect = tc.GetTabRect(hoverTab_index);

            if (dragTabRect.Width < hoverTabRect.Width)
            {
                Point tcLocation = tc.PointToScreen(tc.Location);

                if (dragTab_index < hoverTab_index)
                {
                    if ((e.X - tcLocation.X) > ((hoverTabRect.X + hoverTabRect.Width) - dragTabRect.Width))
                        this.swapTabPages(tc, dragTab, hoverTab);
                }
                else if (dragTab_index > hoverTab_index)
                {
                    if ((e.X - tcLocation.X) < (hoverTabRect.X + dragTabRect.Width))
                        this.swapTabPages(tc, dragTab, hoverTab);
                }
            }
            else this.swapTabPages(tc, dragTab, hoverTab);

            // select new pos of dragTab
            tc.SelectedIndex = tc.TabPages.IndexOf(dragTab);
        }

        private int getHoverTabIndex(TabControl tc)
        {
            for (int i = 0; i < tc.TabPages.Count; i++)
            {
                if (tc.GetTabRect(i).Contains(tc.PointToClient(Cursor.Position)))
                    return i;
            }

            return -1;
        }

        private void swapTabPages(TabControl tc, TabPage src, TabPage dst)
        {
            int index_src = tc.TabPages.IndexOf(src);
            int index_dst = tc.TabPages.IndexOf(dst);
            tc.TabPages[index_dst] = src;
            tc.TabPages[index_src] = dst;
            tc.Refresh();
        }