string类型的方法 C# 为String类型增加方法详解

namespace MyExtensionMethods 
{ 
  public static class MyExtensions 
  { 
    public static int MyGetLength(this System.String target) 
    { 
      return target.Length; 
    } 
  } 
} 

string str = "dafasdf"; 
int len = str.MyGetLength();