扩展方法

using System;
using System.Collections.Generic;

sealed class MyData
{
double D1,D2,D3;
public MyData(double d1,double d2,double d3)
{
D1 = d1;
D2 = d2;
D3 = d3;
}
public double Sum()
{
return D1 + D2 + D3;
}
}
static class ExtendMyData
{
public static double Average(this MyData md)
{
return md.Sum() / 3;
}
}

public class MyClass
{
public static void RunSnippet()
{
MyData md = new MyData(1,2,6.6);
Console.WriteLine("Sum:{0}",md.Sum());
Console.WriteLine("Average:{0}",md.Average());
}

#region Helper methods

public static void Main()
{
try
{
RunSnippet();
}
catch (Exception e)
{
string error = string.Format("--- The following error occurred while executing the snippet: {0} ---", e.ToString());
Console.WriteLine(error);
}
finally
{
Console.Write("Press any key to continue...");
Console.ReadKey();
}
}

private static void WL(object text, params object[] args)
{
Console.WriteLine(text.ToString(), args);
}

private static void RL()
{
Console.ReadLine();
}

private static void Break()
{
System.Diagnostics.Debugger.Break();
}

#endregion
}