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Let's be honest - writing sorting code ranks right up there with client side script validation! - tedious, boring, horrible code that gets in the way of doing more interesting things.  It is repetitive and predictable.  This article will introduce a way to use one "sorter" for all your sorting requirements, amen.

Reflection is a wonderful technology which has been implemented through a powerful yet easy to use API in the Microsoft .NET Framework.  The basic idea is to use code to look back at objects, methods, properties and other parts of your code. See the System.Reflection namespace documentation for more details.

The Basics of Sorting

The .NET framework already provides the general purpose QuickSort algorithm for sorting in the form of the System.Collections.ArrayList.Sort and System.Array.Sort methods which allow for sorting an ArrayList and an Array respectively.  That takes care of the algorithm, but what about the individual evaluation as the elements are compared?  How do those algorithm implementations do their evaluation?  They use the System.IComparable interface which takes the object to be compared to and returns an integer result.  The basic types all implement System.IComparable such as int, string, DateTime, etc.

How do you get these algorithms to sort your own custom objects?  There are overloads on the Sort methods which take a System.Collections.IComparer.  This is an interface which can be implemented to provide your own custom evaluation of two objects.  Since the Microsoft Design Guidelines indicates that properties should be used to represent available information on objects then it is logical to think that your sort should be able to order your objects by their properties.

Sorting Custom Objects

The Thycotic.Collections.dll provides this exact functionality.  It provides a PropertyComparer implementation of IComparer that allows you to sort your Array or ArrayList using one or more properties in ascending or descending order.

 
using Thycotic.Collections;

Pet[] pets = new Pet[4]; 
Pet pet1 = new Dog("Indiana", 3); 
Pet pet2 = new Dog("Rajiv", 3); 
Pet pet3 = new Dog("Chewey", 5); 
Pet pet4 = new Dog("Indiana", 5); 
pets[0] = pet1; 
pets[1] = pet2; 
pets[2] = pet3; 
pets[3] = pet4; 

PropertyComparer comparer = new PropertyComparer(); 
comparer.AddPropertyName("Name", CompareOrder.Ascending); 
comparer.AddPropertyName("Age", CompareOrder.Descending); 

Array.Sort(pets,comparer); 

The simple code snippet above creates an array of Pets (specifically Dogs) and then sorts them by their Name property ascending and the Age descending.  The PropertyComparer has no prior knowledge of the Pet class and does not need to since it uses Reflection to access the properties.