List<String> strList =newList<String>
for(int i =0; i<strList.Count; i++)
{
  strList.RemoveAt(i);
}

List<String> strList =newList<String>
for(int i =0; i<strList.Count; i++)
{
  strList.RemoveAt(i);
  i-=1;
}

public const String str="First Version";

Int32 a=3;
Object obj=new object();
//这里装箱成功，不会失败
obj=i;
//拆箱一定会失败
Int64 b=(Int64)obj;

Int64 b =(Int64)(Int32)obj;

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace UseOperator
{
  class Program
  {
    static void Main(string[] args)
    {
      Test t1 = new Test();
      t1.MyFun();
      Console.ReadLine();
    }
  }
  class Test
  {
    public void MyFun()
    {
      Test t = new Test();
      if (t == null)
      {
        Console.WriteLine("t为空！");
      }
      else
      {
        Console.WriteLine("t不为空！");
      }
    }
    //存在BUG的重载运算法
    public static bool operator ==(Test t1, Test t2)
    {
      return t2.Equals(t1);
    }
    public static bool operator !=(Test t1, Test t2)
    {
      return !(t1 == t2);
    } 
    //覆盖HashCode
    public override int GetHashCode()
    {
      return base.GetHashCode();
    }
    public override bool Equals(object obj)
    {
      return base.Equals(obj);
    }
  }
}

public static bool operator ==(Test t1, Test t2)
{
  if ((t2 as object) == null)
  {
    return (t1 as object) == null;
  }
  else
  {
    return t2.Equals(t1);
  }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace FransferVirtualFunction
{
  class Program
  {
    static void Main(string[] args)
    {
      try
      {
        Child ch = new Child();
      }
      catch (Exception ex)
      {
        Console.WriteLine(ex.Message);
      }
      Console.Read();

    }
  }
  public class Ref
  {
    public string Str = "这是Ref类的一个成员";
  }
  public class Parent
  {
    protected Ref my;
    public Parent()
    {
      my = new Ref();
      //构造方法中调用了虚方法
      Console.WriteLine(GetString());
    }
    //虚方法
    public virtual string GetString()
    {
      return my.Str;    //使用了内部成员
    }
  }
  public class Child : Parent
  {
    private Ref my2;
    public Child()
      : base()
    {
      my2 = new Ref();
    }
    //重写虚方法
    public override string GetString()
    {
      return my2.Str;    //使用了内部成员
    }
  }
}