Generic Multi-Field/Property Sorting for Lists of Business Objects

using System;
using System.Collections.Generic;
using System.Text;
using System.Reflection;

namespace MultiSortDemo
{
    /// <summary>
    /// Used on Properties
    /// This attribute specifies which underlying field name the property is associated with.
    /// </summary>
    [AttributeUsage(AttributeTargets.Property)]
    public class PropertyFieldName : System.Attribute
    {
        protected string sFieldName;
        public PropertyFieldName(string fieldName) { sFieldName = fieldName; }
        public string FieldName { get { return sFieldName; } }
    }

    public class PropertyFieldMappings<T> where T : class
    {
        /// <summary>
        /// Set up a hashtable for quick lookup of field names associated with a property name
        /// </summary>
        private static Dictionary<string, string> htPropertyFieldMapping = new Dictionary<string, string>(16);

        public string GetFieldNameForProperty(string sPropertyName)
        {
            string sFieldName;

            // Check the hashtable/dictionary to see if we have already mapped this field-property association
            if (htPropertyFieldMapping.TryGetValue(sPropertyName, out sFieldName))
            {
                return sFieldName;
            }

            PropertyInfo propInfo = typeof(T).GetProperty(sPropertyName);
            if (propInfo == null)
            {
                throw new Exception("Property name " + sPropertyName + " not found on class type " + typeof(T).Name);
            }

            object[] rgCustomAttributes = propInfo.GetCustomAttributes(typeof(PropertyFieldName), true);
            if (rgCustomAttributes == null || rgCustomAttributes.Length == 0)
            {
                throw new Exception("Property " + sPropertyName + " is not marked with the PropertyFieldName attribute");
            }

            PropertyFieldName propFieldName = (PropertyFieldName)rgCustomAttributes[0];
            sFieldName = propFieldName.FieldName;

            // Now that we have the field name, confirm it exists
            FieldInfo fieldInfo = typeof(T).GetField(
                sFieldName, BindingFlags.FlattenHierarchy | BindingFlags.Instance |
                BindingFlags.Public | BindingFlags.Static | BindingFlags.NonPublic);

            // All is okay, add the mapping to the hashtable/dictionary
            htPropertyFieldMapping.Add(sPropertyName, sFieldName);

            return sFieldName;
        }
    }
}