The following code demonstrates the Sort and Sort method overloads on a simple business object. Calling the Sort method results in the use of the default comparer for the Part type, and the Sort method is implemented using an anonymous method.
using System;
using System.Collections.Generic;
// Simple business object. A PartId is used to identify the type of part
// but the part name can change.
public class Part : IEquatable<Part> , IComparable<Part>
{
public string PartName { get; set; }
public int PartId { get; set; }
public override string ToString()
{
return "ID: " + PartId + " Name: " + PartName;
}
public override bool Equals(object obj)
{
if (obj == null) return false;
Part objAsPart = obj as Part;
if (objAsPart == null) return false;
else return Equals(objAsPart);
}
public int SortByNameAscending(string name1, string name2)
{
return name1.CompareTo(name2);
}
// Default comparer for Part type.
public int CompareTo(Part comparePart)
{
// A null value means that this object is greater.
if (comparePart == null)
return 1;
else
return this.PartId.CompareTo(comparePart.PartId);
}
public override int GetHashCode()
{
return PartId;
}
public bool Equals(Part other)
{
if (other == null) return false;
return (this.PartId.Equals(other.PartId));
}
// Should also override == and != operators.
}
public class Example
{
public static void Main()
{
// Create a list of parts.
List<Part> parts = new List<Part>();
// Add parts to the list.
parts.Add(new Part() { PartName = "regular seat", PartId = 1434 });
parts.Add(new Part() { PartName= "crank arm", PartId = 1234 });
parts.Add(new Part() { PartName = "shift lever", PartId = 1634 }); ;
// Name intentionally left null.
parts.Add(new Part() { PartId = 1334 });
parts.Add(new Part() { PartName = "banana seat", PartId = 1444 });
parts.Add(new Part() { PartName = "cassette", PartId = 1534 });
// Write out the parts in the list. This will call the overridden
// ToString method in the Part class.
Console.WriteLine("\nBefore sort:");
foreach (Part aPart in parts)
{
Console.WriteLine(aPart);
}
// Call Sort on the list. This will use the
// default comparer, which is the Compare method
// implemented on Part.
parts.Sort();
Console.WriteLine("\nAfter sort by part number:");
foreach (Part aPart in parts)
{
Console.WriteLine(aPart);
}
// This shows calling the Sort(Comparison(T) overload using
// an anonymous method for the Comparison delegate.
// This method treats null as the lesser of two values.
parts.Sort(delegate(Part x, Part y)
{
if (x.PartName == null && y.PartName == null) return 0;
else if (x.PartName == null) return -1;
else if (y.PartName == null) return 1;
else return x.PartName.CompareTo(y.PartName);
});
Console.WriteLine("\nAfter sort by name:");
foreach (Part aPart in parts)
{
Console.WriteLine(aPart);
}
/*
Before sort:
ID: 1434 Name: regular seat
ID: 1234 Name: crank arm
ID: 1634 Name: shift lever
ID: 1334 Name:
ID: 1444 Name: banana seat
ID: 1534 Name: cassette
After sort by part number:
ID: 1234 Name: crank arm
ID: 1334 Name:
ID: 1434 Name: regular seat
ID: 1444 Name: banana seat
ID: 1534 Name: cassette
ID: 1634 Name: shift lever
After sort by name:
ID: 1334 Name:
ID: 1444 Name: banana seat
ID: 1534 Name: cassette
ID: 1234 Name: crank arm
ID: 1434 Name: regular seat
ID: 1634 Name: shift lever
*/
}
}