c#动态向类添加方法

namespace ExtensionMethods
{
	public static class MyExtensions
	{
		public static int WordCount(this String str)
		{
			return str.Split(new char[] { ' ', '.', '?' }, StringSplitOptions.RemoveEmptyEntries).Length;
		}
	}
}

string s = "Hello Extension Methods";
int i = s.WordCount();