linq之Capacity（转载）
出处：博客园
作者：mumuliang
连接：http://www.cnblogs.com/mumuliang/p/3914425.html
Capacity
在.NET中List的容量应该只是受到硬件限制。
属性Capacity的真正含义，是创建List时给它预分配的容量。
一旦项的数量超过了当前的Capacity，Capacity会以
Capacity = (Capacity==0)?A_VALUE_YOU_CANNOT_SURE:(Capacity*2)
的方式增长。
当使用默认构造函数创建一个List时，Capacity就是0。（或者你非要用一个0作为capacity参数调用构造）
所以当Capacity是0时，我们为List添加了第一个项目后，Capacity是多少呢？
对，是A_VALUE_YOU_CANNOT_SURE。
不过，在.NET2.0和.NET4.5中，这个值看上去都是4。
System.Diagnostics.Debug.WriteLine(string.Format("default capacity is : {0}", new List<string>().Capacity));
int initCapacity = 0;
List<string> l = new List<string>(initCapacity);
System.Diagnostics.Debug.WriteLine(string.Format("constructe a list with capacity: {0}", l.Capacity));
for (int u = 0; u < 65; ++u)
{
System.Diagnostics.Debug.WriteLine(string.Format("Count: {0}, Capacity: {1}", l.Count, l.Capacity));
//l.TrimExcess();
//System.Diagnostics.Debug.WriteLine(string.Format(" TrimExcess() -> Count: {0}, Capacity: {1}", l.Count, l.Capacity));
l.Add("1");
}
输出
default capacity is :
constructe a list with capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
Count: , Capacity:
TrimExcess()
TrimExcess()的意思就是，如果Capacity大于Count，清掉哪些没有使用的空间。基本上可以理解成让Capacity等于Count，只是基本上，不能信赖这一点。.NET毕竟还要考虑很多性能问题。TrimExcess method does nothing if the list is at more than 90 percent of capacity——这就是.NET的方式。实际上把上面那段代码中的注释放开，就会看到确实存在Capacity和Count不等的情况（然而，并不是90%哟）。Capacity不够以后的增长规则，仍然是*2，并不会因为被Trim过就只是加1。
放开注释后的输出
default capacity is :
constructe a list with capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
发现并不是90%以后
System.Diagnostics.Debug.WriteLine(string.Format("default capacity is : {0}", new List<string>().Capacity));
int initCapacity = ;
List<string> l = new List<string>(initCapacity);
System.Diagnostics.Debug.WriteLine(string.Format("constructe a list with capacity: {0}", l.Capacity));
int initCount = ;
for (int u = ; u < initCount; ++u)
{
l.Add(u.ToString());
}
for (int u = ; u < initCount; ++u)
{
System.Diagnostics.Debug.WriteLine(string.Format("Count: {0}, Capacity: {1}", l.Count, l.Capacity));
l.TrimExcess();
System.Diagnostics.Debug.WriteLine(string.Format(" TrimExcess() -> Count: {0}, Capacity: {1}", l.Count, l.Capacity));
l.Remove(u.ToString());
}
得到
default capacity is :
constructe a list with capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
Count: , Capacity:
TrimExcess() -> Count: , Capacity:
貌似条件是酱紫的
if( count<(int)Math.Floor((double)capacity*0.9) )
do trim
linq之Capacity（转载）的更多相关文章
- linq to sql转载
LINQ简介 LINQ:语言集成查询(Language INtegrated Query)是一组用于c#和Visual Basic语言的扩展.它允许编写C#或者Visual Basic代码以查询数据库 ...
- 30分钟LINQ教程 【转载】
原文地址:http://www.cnblogs.com/liulun/archive/2013/02/26/2909985.html 在说LINQ之前必须先说说几个重要的C#语言特性 一:与LINQ有 ...
- 转载有个小孩跟我说LINQ(重点讲述Linq中GroupBy的原理及用法)
转载原出处: http://www.cnblogs.com/AaronYang/archive/2013/04/02/2994635.html 小孩LINQ系列导航:(一)(二)(三)(四)(五)(六 ...
- 【转载】ADO.NET与ORM的比较(3):Linq to SQL实现CRUD
[转载]ADO.NET与ORM的比较(3):Linq to SQL实现CRUD 说明:个人感觉在Java领域大型开发都离不了ORM的身影,所谓的SSH就是Spring+Struts+Hibernate ...
- 转载一篇文章：LINQ TO SQL 大全
https://www.cnblogs.com/chenwolong/p/lts.html 最近悟出来一个道理,在这儿分享给大家:学历代表你的过去,能力代表你的现在,学习代表你的将来. 十年河东十年河 ...
- linq之将IEnumerable<T>类型的集合转换为DataTable类型 （转载）
在考虑将表格数据导出成excel的时候,网上搜的时候找到一个特别合适的公共方法,可以将query查询出来的集合转换为datatable 需引用using System.Reflection; publ ...
- SQL,LINQ,Lambda语法对照图（转载）
如果你熟悉SQL语句,当使用LINQ时,会有似曾相识的感觉.但又略有不同.下面是SQL和LINQ,Lambda语法对照图 SQL LINQ Lambda SELECT * FROM HumanReso ...
- LINQ to SQL更新数据库操作（转载）
使用LINQ to SQL建模Northwind数据库 在这之前一起学过LINQ to SQL设计器的使用,下面就使用如下的数据模型: 当使用LINQ to SQL设计器设计以上定义的五个类(Prod ...
- 转载linq to sql 的详解
[转]LINQ To SQL 语法及实例大全 2011-11-26阅读38651 评论9 LINQ to SQL语句(1)之Where Where操作 适用场景:实现过滤,查询等功能. 说明:与SQL ...
随机推荐
- linux系统使用sh文件传参数给matlab程序
linux系统下使用sh文件传参数给matlab程序 (1)编写sh文件 程序以下面的行开始(必须在文件的第一行): #!/bin/sh 定义需要传递的参数,用双引号引起,参数之间使用逗号或分 ...
- 查看linux操作系统的版本等信息
1.查看操作系统是32位还是64位的命令: (1)getconf LONG_BIT (2)uname -a (3)uname -m (4)arch (5)file /sbin/init 2.查看操作系 ...
- 类1(this指针/const成员函数/类作用域/外部成员函数/返回this对象的函数)
假设我们要设计一个包含以下操作的 Sales_data 类: 1.一个 isbn 成员函数,用于返回对象的 book_no 成员变量 2.一个 combine 成员函数,用于将一个 Sales_dat ...
- centos7用docker安装单节点redis4.0.11
[root@localhost conf]# docker search redisINDEX NAME DESCRIPTION STARS OFFICIAL AUTOMATEDdocker.io d ...
- html基础知识，整理
# HMTL 基础知识 ###查看网页源代码吗 ``` ctrl + u``` ###dom元素 一个标签即代表一个dom元素 ###dom元素属性 ``` <p id ="first ...
- 查看db连接数sql
/****** Object: StoredProcedure [dbo].[SP_Conn] Script Date: 12/09/2018 19:03:28 ******/ SET ANSI_NU ...
- springcloud微服务config的使用
首先需要建立一个server端: pom依赖中加入 <dependency> <groupId>org.springframework.cloud</groupId> ...
- mac 添加环境变量
1.Mac系统的环境变量,加载顺序为: a. /etc/profile b. /etc/paths c. ~/.bash_profile d. ~/.bash_login e. ~/.profile ...
- oracle三种连接身份
登录oracle数据库有三种连接身份 sysdba:数据库管理员,sysyoper:数据库操作员,normal:普通用户. "sysdba" 即数据库管理员 权限包括: 打 ...
- Luogu P1801 黑匣子_NOI导刊2010提高（06）
P1801 黑匣子_NOI导刊2010提高(06) 题目描述 Black Box是一种原始的数据库.它可以储存一个整数数组,还有一个特别的变量i.最开始的时候Black Box是空的．而i等于0.这个 ...