Simple PropertyComparer

Introduction

This article is about a simple PropertyComparer class that can be used to sort collections of objects by property of the objects in the collection:

using System;
using System.Collections;
using System.Collections.Generic;
using System.Reflection;
using System.Web.UI.WebControls;

namespace yourNamespace
{
    public class PropertyComparer<T> : IComparer<T>
    {
        private PropertyInfo property;
        private SortDirection sortDirection;

        public PropertyComparer(string sortProperty, SortDirection sortDirection)
        {
            property = typeof (T).GetProperty(sortProperty);
            Utils.AssertIsNotNull(
                string.Format("Property {0} not found on type {1}", sortProperty,
                              typeof (T).FullName), sortProperty);
            this.sortDirection = sortDirection;
        }

        public int Compare(T x, T y)
        {
            object valueX = property.GetValue(x, null);
            object valueY = property.GetValue(y, null);
            
            if (sortDirection == SortDirection.Ascending)
            {
                return Comparer.Default.Compare(valueX, valueY);
            }
            else
            {
                return Comparer.Default.Compare(valueY, valueX);
            }
        }
    }
}

Usage

Here is an example of using the PropertyComparer to sort a collection of objects:

    public class ObjectInCollectionType
    {
        private string text = Guid.NewGuid().ToString();

        public string Text
        {
            get { return text; }
            set { text = value; }
        }
    }
    public class TestPropertyComparer
    {
        public static void Test()
        {
            List<ObjectInCollectionType> myList = new List<ObjectInCollectionType>();
            myList.Add(new ObjectInCollectionType());
            myList.Add(new ObjectInCollectionType());
            myList.Add(new ObjectInCollectionType());
            myList.Add(new ObjectInCollectionType());
            // Sorting the collection
            myList.Sort(new PropertyComparer<ObjectInCollectionType>
                ("Text", SortDirection.Ascending));
        }
    }

Happy programming.

History

• 1^st November, 2006: Initial post