EnsureVisible for ListViewSubItem

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Introduction 

It extends the ListView control and adds an EnsureVisible method to scroll horizontally to a subitem.

Background   

I often use The Code Project to find good samples, but I didn't find one for this. So I just want to give something back.    

Using the Code 

The native Windows message to scroll the listview is:

const Int32 LVM_FIRST = 0x1000;
const Int32 LVM_SCROLL = LVM_FIRST + 20;

[DllImport("user32")]
static extern IntPtr SendMessage(IntPtr Handle, Int32 msg, IntPtr wParam,
IntPtr lParam);

private void ScrollHorizontal(int pixelsToScroll)
{
    SendMessage(this.Handle, LVM_SCROLL, (IntPtr)pixelsToScroll,
    IntPtr.Zero);
}

The public method to call with item to scroll to is as follows:

    /// <summary>
    /// Ensure visible of a ListViewItem and SubItem Index.
    /// </summary>
    /// <param name="item"></param>
    /// <param name="subItemIndex"></param>
    public void EnsureVisible(ListViewItem item, int subItemIndex)
    {
        if (item == null || subItemIndex > item.SubItems.Count - 1)
        {
            throw new ArgumentException();
        }

        // scroll to the item row.
        item.EnsureVisible();
        Rectangle bounds = item.SubItems[subItemIndex].Bounds;

        // need to set width from columnheader, first subitem includes
        // all subitems.
        bounds.Width = this.Columns[subItemIndex].Width;

        ScrollToRectangle(bounds);
    }

    /// <summary>
    /// Scrolls the listview.
    /// </summary>
    /// <param name="bounds"></param>
    private void ScrollToRectangle(Rectangle bounds)
    {
        int scrollToLeft = bounds.X + bounds.Width + MARGIN;
        if (scrollToLeft > this.Bounds.Width)
        {
            this.ScrollHorizontal(scrollToLeft - this.Bounds.Width);
        }
        else
        {
            int scrollToRight = bounds.X - MARGIN;
            if (scrollToRight < 0)
            {
                this.ScrollHorizontal(scrollToRight);
            }
        }
    }
}

History

• 30^th September, 2008: Initial post