xenadmin/XenAdmin/Controls/ListViewColumnSorter.cs

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using System;
using System.Collections;
using System.Windows.Forms;

using XenAdmin.Core;

namespace XenAdmin.Controls
{
    /// <summary>
    /// This class is an implementation of the 'IComparer' interface. Sorts using StringUtility.NaturalCompare.
    /// See http://support.microsoft.com/kb/319401.
    /// </summary>
    public class ListViewColumnSorter : IComparer
    {
        /// <summary>
        /// Specifies the column to be sorted
        /// </summary>
        private int ColumnToSort;
        /// <summary>
        /// Specifies the order in which to sort (i.e. 'Ascending').
        /// </summary>
        private SortOrder OrderOfSort;

        private Comparison<ListViewItem.ListViewSubItem> comparer;
        /// <summary>
        /// The Comparison that is used. If set to null, StringUtility.NaturalCompare will be used. The default value is null.
        /// </summary>
        public Comparison<ListViewItem.ListViewSubItem> Comparer
        {
            get
            {
                return comparer;
            }
            set
            {
                comparer = value;
            }
        }

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

            // Initialize the sort order to 'none'
            OrderOfSort = SortOrder.None;
        }

        /// <summary>
        /// This method is inherited from the IComparer interface.
        /// </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;
            ListViewItem listviewX, listviewY;

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

            if (listviewX.SubItems.Count == 0 || listviewY.SubItems.Count == 0)
                return 0;
            else if (comparer == null)
            {
                if (listviewX.SubItems.Count > ColumnToSort && listviewY.SubItems.Count > ColumnToSort)
                    compareResult = StringUtility.NaturalCompare(listviewX.SubItems[ColumnToSort].Text, listviewY.SubItems[ColumnToSort].Text);
                else
                    compareResult = StringUtility.NaturalCompare(listviewX.SubItems[0].Text, listviewY.SubItems[0].Text);
            }
            else
            {
                if (listviewX.SubItems.Count > ColumnToSort && listviewY.SubItems.Count > ColumnToSort)
                    compareResult = comparer(listviewX.SubItems[ColumnToSort], listviewY.SubItems[ColumnToSort]);
                else
                    compareResult = comparer(listviewX.SubItems[0], listviewY.SubItems[0]);
            }

            // 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;
            }
        }

    }
}