ListView Column Sorter

using System;
using System.Collections;
using System.Text.RegularExpressions;	
using System.Windows.Forms;
using System.Globalization;

namespace ListViewSorter
{
	/// <summary>
	/// This class is an implementation of the 'IComparer' interface.
	/// </summary>
	public class ListViewColumnSorter : IComparer
	{
        public enum SortModifiers
        {
            SortByImage,
            SortByCheckbox,
            SortByText
        }

		/// <summary>
		/// Specifies the column to be sorted
		/// </summary>
		public int ColumnToSort;
		/// <summary>
		/// Specifies the order in which to sort (i.e. 'Ascending').
		/// </summary>
        public SortOrder OrderOfSort;
		/// <summary>
		/// Case insensitive comparer object
		/// </summary>
		
		private NumberCaseInsensitiveComparer ObjectCompare;
		private ImageTextComparer FirstObjectCompare;
        private CheckboxTextComparer FirstObjectCompare2;

        private SortModifiers mySortModifier = SortModifiers.SortByText;
        public SortModifiers _SortModifier
        {
            set
            {
                mySortModifier = value;
            }
            get
            {
                return mySortModifier;
            }
        }

		/// <summary>
		/// Class constructor.  Initializes various elements
		/// </summary>
		public ListViewColumnSorter()
		{
			// Initialize the column to '0'
			ColumnToSort = 0;

			// Initialize the CaseInsensitiveComparer object
			ObjectCompare = new NumberCaseInsensitiveComparer();
			FirstObjectCompare = new ImageTextComparer();
            FirstObjectCompare2 = new CheckboxTextComparer();
		}

		/// <summary>
		/// This method is inherited from the IComparer interface.  It compares the two objects passed using a case insensitive comparison.
		/// </summary>
		/// <param name="x">First object to be compared</param>
		/// <param name="y">Second object to be compared</param>
		/// <returns>The result of the comparison. "0" if equal, negative if 'x' is less than 'y' and positive if 'x' is greater than 'y'</returns>
		public int Compare(object x, object y)
		{
			int compareResult = 0;
			ListViewItem listviewX, listviewY;

			// Cast the objects to be compared to ListViewItem objects
			listviewX = (ListViewItem)x;
			listviewY = (ListViewItem)y;

            ListView listViewMain = listviewX.ListView;

            // Calculate correct return value based on object comparison
            if (listViewMain.Sorting != SortOrder.Ascending &&
                listViewMain.Sorting != SortOrder.Descending)
            {
                // Return '0' to indicate they are equal
                return compareResult;
            }

            if (mySortModifier.Equals(SortModifiers.SortByText) || ColumnToSort > 0)
            {
                // Compare the two items

                if (listviewX.SubItems.Count <= ColumnToSort &&
                    listviewY.SubItems.Count <= ColumnToSort)
                {
                    compareResult = ObjectCompare.Compare(null, null);
                }
                else if (listviewX.SubItems.Count <= ColumnToSort &&
                         listviewY.SubItems.Count > ColumnToSort)
                {
                    compareResult = ObjectCompare.Compare(null, listviewY.SubItems[ColumnToSort].Text.Trim());
                }
                else if (listviewX.SubItems.Count > ColumnToSort && listviewY.SubItems.Count <= ColumnToSort)
                {
                    compareResult = ObjectCompare.Compare(listviewX.SubItems[ColumnToSort].Text.Trim(), null);
                }
                else
                {
                    compareResult = ObjectCompare.Compare(listviewX.SubItems[ColumnToSort].Text.Trim(), listviewY.SubItems[ColumnToSort].Text.Trim());
                }
            }
            else
            {
                switch (mySortModifier)
                {
                    case SortModifiers.SortByCheckbox:
                        compareResult = FirstObjectCompare2.Compare(x, y);
                        break;
                    case SortModifiers.SortByImage:
                        compareResult = FirstObjectCompare.Compare(x, y);
                        break;
                    default:
                        compareResult = FirstObjectCompare.Compare(x, y);
                        break;
                }
            }

            // Calculate correct return value based on object comparison
            if (OrderOfSort == SortOrder.Ascending)
            {
                // Ascending sort is selected, return normal result of compare operation
                return compareResult;
            }
            else if (OrderOfSort == SortOrder.Descending)
            {
                // Descending sort is selected, return negative result of compare operation
                return (-compareResult);
            }
            else
            {
                // Return '0' to indicate they are equal
                return 0;
            }
        }
    
		/// <summary>
		/// Gets or sets the number of the column to which to apply the sorting operation (Defaults to '0').
		/// </summary>
		public int SortColumn
		{
			set
			{
				ColumnToSort = value;
			}
			get
			{
				return ColumnToSort;
			}
		}

		/// <summary>
		/// Gets or sets the order of sorting to apply (for example, 'Ascending' or 'Descending').
		/// </summary>
        public SortOrder Order
		{
			set
			{
				OrderOfSort = value;
			}
			get
			{
				return OrderOfSort;
			}
		}
    
	}

	public class ImageTextComparer : IComparer
	{
		//private CaseInsensitiveComparer ObjectCompare;
		private NumberCaseInsensitiveComparer ObjectCompare;
        
		public ImageTextComparer()
		{
			// Initialize the CaseInsensitiveComparer object
			ObjectCompare = new NumberCaseInsensitiveComparer();
		}

		public int Compare(object x, object y)
		{
			//int compareResult;
			int image1, image2;
			ListViewItem listviewX, listviewY;

			// Cast the objects to be compared to ListViewItem objects
			listviewX = (ListViewItem)x;
			image1 = listviewX.ImageIndex;
			listviewY = (ListViewItem)y;
			image2 = listviewY.ImageIndex;

			if (image1 < image2)
			{
				return -1;
			}
			else if (image1 == image2)
			{
                return ObjectCompare.Compare(listviewX.Text.Trim(), listviewY.Text.Trim());
			}
			else
			{
				return 1;
			}
		}
	}

    public class CheckboxTextComparer : IComparer
    {
        private NumberCaseInsensitiveComparer ObjectCompare;

        public CheckboxTextComparer()
        {
            // Initialize the CaseInsensitiveComparer object
            ObjectCompare = new NumberCaseInsensitiveComparer();
        }

        public int Compare(object x, object y)
        {
            // Cast the objects to be compared to ListViewItem objects
            ListViewItem listviewX = (ListViewItem)x;
            ListViewItem listviewY = (ListViewItem)y;

            if (listviewX.Checked && !listviewY.Checked)
            {
                return -1;
            }
            else if (listviewX.Checked.Equals(listviewY.Checked))
            {
                if (listviewX.ImageIndex < listviewY.ImageIndex)
                {
                    return -1;
                }
                else if (listviewX.ImageIndex == listviewY.ImageIndex)
                {
                    return ObjectCompare.Compare(listviewX.Text.Trim(), listviewY.Text.Trim());
                }
                else
                {
                    return 1;
                }
            }
            else
            {
                return 1;
            }
        }
    }


	public class NumberCaseInsensitiveComparer : CaseInsensitiveComparer
	{
		public NumberCaseInsensitiveComparer ()
		{
			
		}
        
        public new int Compare(object x, object y)
		{
            if (x == null && y == null)
            {
                return 0;
            }
            else if (x == null && y != null)
            {
                return -1;
            }
            else if (x != null && y == null)
            {
                return 1;
            }

            if ((x is System.String) && IsDecimalNumber((string)x) && (y is System.String) && IsDecimalNumber((string)y))
			{
                try
                {
                    decimal xx= Decimal.Parse(((string)x).Trim());
                    decimal yy= Decimal.Parse(((string)y).Trim());

                    return base.Compare(xx,yy);
                }
                catch
                {
                    return -1;
                }
            }
			else
			{
				return base.Compare(x,y);
			}
		}

        // deprecated
        //private bool IsWholeNumber(string strNumber)
        //{
        //    Regex wholePattern = new Regex(@"^\d+$");
        //    return wholePattern.IsMatch(strNumber);
        //}

        private string GetNumberDecimalSeparator()
        {
            return System.Globalization.CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator;
        }

        // http://stackoverflow.com/questions/4246077/matching-numbers-with-regular-expressions-only-digits-and-commas/4247184#4247184
        // https://www.debuggex.com/r/Lyx0F0y1LORvNhwA
        private bool IsDecimalNumber(string strNumber)
        {
            //@"^-?(\d+|(\d{1,3}((,|\.)\d{3})*))((,|\.)\d+)?$"

            //string regex = @"^-?(?:(?:0|[1-9][0-9]*)(?:" + GetNumberDecimalSeparator() + @"[0-9]+)?|[1-9][0-9]{1,2}(?:,[0-9]{3})+)$";

            string regex = @"^-?(\d+|(\d{1,3}((,|\.)\d{3})*))((,|\.)\d+)?$";

            Regex wholePattern = new Regex(regex);
            return wholePattern.IsMatch(strNumber);
        }
	}

}