C# · 12月 20, 2021

五、谈扩展方法的理解

为什么要用扩展方法

在说什么是扩展方法之前我们先来说说为什么要用扩展方法。

首先我们定义一个  类:

DateTime BirthTime { ; DateTime? DeathTime { ; }

加入这个类来自第三方的dll引用,且现在我们需要添加一个方法  获取年龄。你可能会想到自己定一个子类继承:

(DeathTime.Value – BirthTime).Days / (DateTime.Now – BirthTime).Days /

是的,这样可以实现我们的需求。不过实现新增的方法就去继承真的是最合适的吗()? 如果上面定义的密封类呢?  Person ,这个时候是不能继承的,我们只能另想办法。

随意写个静态类:

(person.DeathTime.Value – person.BirthTime).Days / (DateTime.Now – person.BirthTime).Days /

然后调用  ,是的看似不错。可是这和我们说的扩展方法有什么关系呢?下面就是见证奇迹的时候了。

其他的任何地方都不变,唯一变化的是在参数前面加里this关键字。对,是的,仅仅如此它就变成了我们今天要讲的扩展方法。

调用如:  age = p.GetAge(); 相比上面的  更简单明了。

这里我们说的是在需要扩展密封类的方法时,我们可以使用到扩展方法。还有一种情况就是,在需要扩展接口的时候时候我们更加需要。比如,需要扩展IList的排序。我们要么写个扩展方法,要么是继承实现接口()。我想你心中已经有了答案选择哪种方式。

扩展方法到底是什么

我们看到上面使用的扩展方法,有没有感觉很神奇。仅仅多添加了一个this关键字就直接可以当成扩展方法使用了。那扩展方法到底是什么东东,看了上面代码好像和静态方法有着说不清道不明的关系。下面我们继续分析:

分别定义一个静态方法和一个扩展方法

(person.DeathTime.Value – person.BirthTime).Days / (DateTime.Now – person.BirthTime).Days / </span><span style=”color: #0000ff;”&gt;public</span> <span style=”color: #0000ff;”&gt;static</span> <span style=”color: #0000ff;”&gt;int</span> GetAge(<span style=”color: #0000ff;”&gt;this</span><span style=”color: #000000;”&gt; Person person) { </span><span style=”color: #0000ff;”&gt;if</span><span style=”color: #000000;”&gt; (person.DeathTime.HasValue) </span><span style=”color: #0000ff;”&gt;return</span> (person.DeathTime.Value – person.BirthTime).Days / <span style=”color: #800080;”&gt;365</span><span style=”color: #000000;”&gt;; </span><span style=”color: #0000ff;”&gt;else</span> <span style=”color: #0000ff;”&gt;return</span> (DateTime.<a href=”https://www.jb51.cc/tag/Now/” target=”_blank” class=”keywords”>Now</a> – person.BirthTime).Days / <span style=”color: #800080;”&gt;365</span><span style=”color: #000000;”&gt;; }</span></pre>

分别调用:

p = Person() { BirthTime = DateTime.Parse( age == ExtensionClass.GetAge2(p);

编译后的IL代码:

我们看到反编译成IL之后发现两者并无不同。所以,我理解成()。且 扩展方法可以做些什么把已有的静态方法转成扩展方法:如: IsNullOrEmpty(

调用: 

str = isNull = str.IsNullOrEmpty();

 感觉相比期静态方法调用要优雅,更接近我们的自然语言。

 可以编写很多的帮助类,如(): DateTime? MyToDateTime( ( </span><span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<summary></span> <span style=”color: #808080;”&gt;///</span><span style=”color: #008000;”&gt; 转double </span><span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;</summary></span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<param name=”str”&gt;@H_<a href=”https://www.jb51.cc/tag/502/” target=”_blank” class=”keywords”>502</a>_212@</span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<returns></returns></span> <span style=”color: #0000ff;”&gt;public</span> <span style=”color: #0000ff;”&gt;static</span> <span style=”color: #0000ff;”&gt;double</span> MyToDouble(<span style=”color: #0000ff;”&gt;this</span> <span style=”color: #0000ff;”&gt;string</span><span style=”color: #000000;”&gt; str) { </span><span style=”color: #0000ff;”&gt;if</span> (<span style=”color: #0000ff;”&gt;string</span><span style=”color: #000000;”&gt;.IsNullOrEmpty(str)) </span><span style=”color: #0000ff;”&gt;return</span> -<span style=”color: #800080;”&gt;1</span><span style=”color: #000000;”&gt;; </span><span style=”color: #0000ff;”&gt;else</span> <span style=”color: #0000ff;”&gt;return</span> <span style=”color: #0000ff;”&gt;double</span><span style=”color: #000000;”&gt;.Parse(str); } </span><span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<summary></span> <span style=”color: #808080;”&gt;///</span><span style=”color: #008000;”&gt; 转int </span><span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;</summary></span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<param name=”str”&gt;@H_<a href=”https://www.jb51.cc/tag/502/” target=”_blank” class=”keywords”>502</a>_212@</span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<returns></returns></span> <span style=”color: #0000ff;”&gt;public</span> <span style=”color: #0000ff;”&gt;static</span> <span style=”color: #0000ff;”&gt;int</span> MyToInt(<span style=”color: #0000ff;”&gt;this</span> <span style=”color: #0000ff;”&gt;string</span><span style=”color: #000000;”&gt; str) { </span><span style=”color: #0000ff;”&gt;if</span> (<span style=”color: #0000ff;”&gt;string</span><span style=”color: #000000;”&gt;.IsNullOrEmpty(str)) </span><span style=”color: #0000ff;”&gt;return</span> -<span style=”color: #800080;”&gt;1</span><span style=”color: #000000;”&gt;; </span><span style=”color: #0000ff;”&gt;else</span> <span style=”color: #0000ff;”&gt;return</span> <span style=”color: #0000ff;”&gt;int</span><span style=”color: #000000;”&gt;.Parse(str); } </span><span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<summary></span> <span style=”color: #808080;”&gt;///</span><span style=”color: #008000;”&gt; 指示指定的字符串是 null 还是 Sy<a href=”https://www.jb51.cc/tag/stem/” target=”_blank” class=”keywords”>stem</a>.String.Empty 字符串。 </span><span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;</summary></span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<param name=”str”&gt;@H_<a href=”https://www.jb51.cc/tag/502/” target=”_blank” class=”keywords”>502</a>_212@</span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<returns></returns></span> <span style=”color: #0000ff;”&gt;public</span> <span style=”color: #0000ff;”&gt;static</span> <span style=”color: #0000ff;”&gt;bool</span> IsNullOrEmpty(<span style=”color: #0000ff;”&gt;this</span> <span style=”color: #0000ff;”&gt;string</span><span style=”color: #000000;”&gt; str) { </span><span style=”color: #0000ff;”&gt;return</span> <span style=”color: #0000ff;”&gt;string</span><span style=”color: #000000;”&gt;.IsNullOrEmpty(str); } </span><span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<summary></span> <span style=”color: #808080;”&gt;///</span><span style=”color: #008000;”&gt; 如果字符串为null,则返回空字符串。(否则返回原字符串) </span><span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;</summary></span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<param name=”str”&gt;@H_<a href=”https://www.jb51.cc/tag/502/” target=”_blank” class=”keywords”>502</a>_212@</span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<returns></returns></span> <span style=”color: #0000ff;”&gt;public</span> <span style=”color: #0000ff;”&gt;static</span> <span style=”color: #0000ff;”&gt;string</span> GetValueOrEmpty(<span style=”color: #0000ff;”&gt;this</span> <span style=”color: #0000ff;”&gt;string</span><span style=”color: #000000;”&gt; str) { </span><span style=”color: #0000ff;”&gt;if</span><span style=”color: #000000;”&gt; (str.IsNullOrEmpty()) </span><span style=”color: #0000ff;”&gt;return</span> <span style=”color: #0000ff;”&gt;string</span><span style=”color: #000000;”&gt;.Empty; </span><span style=”color: #0000ff;”&gt;return</span><span style=”color: #000000;”&gt; str; }</span></pre>

上面所有的都只是扩展方法的附加用处,扩展方法真正的威力是为Linq服务的(),实现链式编程。下面我们自己来实现所谓的链式编程:

初始化 

List persons = List Person(){ BirthTime=DateTime.Parse( Person(){ BirthTime=DateTime.Parse( Person(){ BirthTime=DateTime.Parse(),DeathTime=DateTime.Parse( Person(){ BirthTime=DateTime.Parse( Person(){ BirthTime=DateTime.Parse( Person(){ BirthTime=DateTime.Parse( Person(){ BirthTime=DateTime.Parse(

需求:1.查询活人。2.按出生日期排序

IList MyWhere( IList list,Func newList = List ( item </span><span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<summary></span> <span style=”color: #808080;”&gt;///</span><span style=”color: #008000;”&gt; 升序排序 </span><span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;</summary></span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<typeparam name=”T”&gt;</typeparam></span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<param name=”list”&gt;@H_<a href=”https://www.jb51.cc/tag/502/” target=”_blank” class=”keywords”>502</a>_212@</span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<param name=”func”&gt;@H_<a href=”https://www.jb51.cc/tag/502/” target=”_blank” class=”keywords”>502</a>_212@</span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<returns></returns></span> <span style=”color: #0000ff;”&gt;public</span> <span style=”color: #0000ff;”&gt;static</span> IList<T> MyOrderBy<T>(<span style=”color: #0000ff;”&gt;this</span> IList<T> list,DateTime><span style=”color: #000000;”&gt; func) { </span><span style=”color: #0000ff;”&gt;if</span> (list.Count() <= <span style=”color: #800080;”&gt;1</span><span style=”color: #000000;”&gt;) </span><span style=”color: #0000ff;”&gt;return</span><span style=”color: #000000;”&gt; list; </span><span style=”color: #0000ff;”&gt;for</span> (<span style=”color: #0000ff;”&gt;int</span> i = <span style=”color: #800080;”&gt;0</span>; i < list.Count(); i++<span style=”color: #000000;”&gt;) { </span><span style=”color: #0000ff;”&gt;for</span> (<span style=”color: #0000ff;”&gt;int</span> j = i + <span style=”color: #800080;”&gt;1</span>; j < list.Count(); j++<span style=”color: #000000;”&gt;) { </span><span style=”color: #0000ff;”&gt;var</span> item1 = list[j – <span style=”color: #800080;”&gt;1</span><span style=”color: #000000;”&gt;]; </span><span style=”color: #0000ff;”&gt;var</span> item2 =<span style=”color: #000000;”&gt; list[j]; </span><span style=”color: #0000ff;”&gt;if</span> ((func(item1) – func(item2)).Ticks > <span style=”color: #800080;”&gt;0</span><span style=”color: #000000;”&gt;) { list[j </span>- <span style=”color: #800080;”&gt;1</span>] =<span style=”color: #000000;”&gt; item2; list[j] </span>=<span style=”color: #000000;”&gt; item1; } } } </span><span style=”color: #0000ff;”&gt;return</span><span style=”color: #000000;”&gt; list; } </span><span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<summary></span> <span style=”color: #808080;”&gt;///</span><span style=”color: #008000;”&gt; 降序排序 </span><span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;</summary></span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<typeparam name=”T”&gt;</typeparam></span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<param name=”list”&gt;@H_<a href=”https://www.jb51.cc/tag/502/” target=”_blank” class=”keywords”>502</a>_212@</span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<param name=”func”&gt;@H_<a href=”https://www.jb51.cc/tag/502/” target=”_blank” class=”keywords”>502</a>_212@</span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<returns></returns></span> <span style=”color: #0000ff;”&gt;public</span> <span style=”color: #0000ff;”&gt;static</span> IList<T> MyOrderByDescending<T>(<span style=”color: #0000ff;”&gt;this</span> IList<T> list,DateTime><span style=”color: #000000;”&gt; func) { </span><span style=”color: #0000ff;”&gt;if</span> (list.Count() <= <span style=”color: #800080;”&gt;1</span><span style=”color: #000000;”&gt;) </span><span style=”color: #0000ff;”&gt;return</span><span style=”color: #000000;”&gt; list; </span><span style=”color: #0000ff;”&gt;for</span> (<span style=”color: #0000ff;”&gt;int</span> i = <span style=”color: #800080;”&gt;0</span>; i < list.Count(); i++<span style=”color: #000000;”&gt;) { </span><span style=”color: #0000ff;”&gt;for</span> (<span style=”color: #0000ff;”&gt;int</span> j = <span style=”color: #800080;”&gt;1</span>; j < list.Count() – i; j++<span style=”color: #000000;”&gt;) { </span><span style=”color: #0000ff;”&gt;var</span> item1 = list[j – <span style=”color: #800080;”&gt;1</span><span style=”color: #000000;”&gt;]; </span><span style=”color: #0000ff;”&gt;var</span> item2 =<span style=”color: #000000;”&gt; list[j]; </span><span style=”color: #0000ff;”&gt;if</span> ((func(item1) – func(item2)).Ticks < <span style=”color: #800080;”&gt;0</span><span style=”color: #000000;”&gt;) { list[j </span>- <span style=”color: #800080;”&gt;1</span>] =<span style=”color: #000000;”&gt; item2; list[j] </span>=<span style=”color: #000000;”&gt; item1; } } } </span><span style=”color: #0000ff;”&gt;return</span><span style=”color: #000000;”&gt; list; }}</span></pre>

调用:()

newPersons = persons.MyWhere(t => t.DeathTime == ).MyOrderByDescending(t => ( item

就是如此简单的实现了所谓的函数式编程。结果图如下:

这样一句代码搞定所有逻辑,像自然语言般的流畅。其实.net为IEnumerable实现了这样的扩展,如:

执行结构和上面一模一样。

其实扩展方法也可以当成静态方法来使用:

p1 = ExtensionClass.MyWhere(persons,t => t.DeathTime == p2 = ExtensionClass.MyOrderByDescending(p1,t => p3 = ExtensionClass.MyOrderBy(p2,t => t.BirthTime);

C#代码:

 

反编译C#的代码:()

反编译的IL代码:

虽然编译后的代码是一样的,但是做为程序员的我们更喜欢哪种方式呢?

我们在对扩展方法的怎么使用疑惑或者忘记了规则的时候,我们不用去查找资料说:

第一个参数是要扩展或者要操作的类型,这称为”被扩展的类型”为了指定扩展方法,要在被扩展的类型名称前面附加this修饰符要将方法作为一个扩展方法来访问,要用using指令导入扩展类型的命名空间,或者使扩展类型和调用代码在同一个命名空间中.

全部代码:

<span style=”color: #0000ff;”>namespace<span style=”color: #000000;”> test
{

</span><span style=”color: #0000ff;”&gt;class</span><span style=”color: #000000;”&gt; Program{ </span><span style=”color: #0000ff;”&gt;static</span> <span style=”color: #0000ff;”&gt;void</span> Main(<span style=”color: #0000ff;”&gt;string</span><span style=”color: #000000;”&gt;[] args) { </span><span style=”color: #008000;”&gt;/*</span><span style=”color: #008000;”&gt; * 1.工具类 * 2.链式编程 </span><span style=”color: #008000;”&gt;*/</span> <span style=”color: #0000ff;”&gt;string</span> str = <span style=”color: #0000ff;”&gt;null</span><span style=”color: #000000;”&gt;; </span><span style=”color: #0000ff;”&gt;var</span> isNull =<span style=”color: #000000;”&gt; str.IsNullOrEmpty(); </span><span style=”color: #0000ff;”&gt;var</span> p = <span style=”color: #0000ff;”&gt;new</span> Person() { BirthTime = DateTime.Parse(<span style=”color: #800000;”&gt;”</span><span style=”color: #800000;”&gt;1990-07-19</span><span style=”color: #800000;”&gt;”</span><span style=”color: #000000;”&gt;) }; </span><span style=”color: #0000ff;”&gt;var</span> age =<span style=”color: #000000;”&gt; p.GetAge(); age </span>=<span style=”color: #000000;”&gt; ExtensionClass.GetAge2(p); List</span><Person> persons = <span style=”color: #0000ff;”&gt;new</span> List<Person><span style=”color: #000000;”&gt;() { </span><span style=”color: #0000ff;”&gt;new</span> Person(){ BirthTime=DateTime.Parse(<span style=”color: #800000;”&gt;”</span><span style=”color: #800000;”&gt;1990-01-19</span><span style=”color: #800000;”&gt;”</span><span style=”color: #000000;”&gt;)},</span><span style=”color: #0000ff;”&gt;new</span> Person(){ BirthTime=DateTime.Parse(<span style=”color: #800000;”&gt;”</span><span style=”color: #800000;”&gt;1991-06-19</span><span style=”color: #800000;”&gt;”</span><span style=”color: #000000;”&gt;)} }; </span><span style=”color: #0000ff;”&gt;var</span> newPersons = persons.MyWhere(t => t.DeathTime == <span style=”color: #0000ff;”&gt;null</span>).MyOrderByDescending(t =><span style=”color: #000000;”&gt; t.BirthTime); </span><span style=”color: #0000ff;”&gt;var</span> p1 = ExtensionClass.MyWhere(persons,t => t.DeathTime == <span style=”color: #0000ff;”&gt;null</span><span style=”color: #000000;”&gt;); </span><span style=”color: #0000ff;”&gt;var</span> p2 = ExtensionClass.MyOrderByDescending(p1,t =><span style=”color: #000000;”&gt; t.BirthTime); </span><span style=”color: #0000ff;”&gt;var</span> p3 = ExtensionClass.MyOrderBy(p2,t =><span style=”color: #000000;”&gt; t.BirthTime); </span><span style=”color: #0000ff;”&gt;foreach</span> (<span style=”color: #0000ff;”&gt;var</span> item <span style=”color: #0000ff;”&gt;in</span><span style=”color: #000000;”&gt; newPersons) { Console.WriteLine(item.BirthTime); } Console.ReadKey(); }}</span><span style=”color: #0000ff;”&gt;public</span> <span style=”color: #0000ff;”&gt;sealed</span> <span style=”color: #0000ff;”&gt;class</span><span style=”color: #000000;”&gt; Person{ </span><span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<summary></span> <span style=”color: #808080;”&gt;///</span><span style=”color: #008000;”&gt; 出生日期 </span><span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;</summary></span> <span style=”color: #0000ff;”&gt;public</span> DateTime BirthTime { <span style=”color: #0000ff;”&gt;get</span>; <span style=”color: #0000ff;”&gt;set</span><span style=”color: #000000;”&gt;; } </span><span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<summary></span> <span style=”color: #808080;”&gt;///</span><span style=”color: #008000;”&gt; 死亡日期 </span><span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;</summary></span> <span style=”color: #0000ff;”&gt;public</span> DateTime? DeathTime { <span style=”color: #0000ff;”&gt;get</span>; <span style=”color: #0000ff;”&gt;set</span><span style=”color: #000000;”&gt;; }}</span><span style=”color: #008000;”&gt;//</span><span style=”color: #008000;”&gt;public class MyPerson : Person</span><span style=”color: #008000;”&gt;//</span><span style=”color: #008000;”&gt;{</span><span style=”color: #008000;”&gt;//</span><span style=”color: #008000;”&gt; public int GetAge()</span><span style=”color: #008000;”&gt;//</span><span style=”color: #008000;”&gt; {</span><span style=”color: #008000;”&gt;//</span><span style=”color: #008000;”&gt; if (DeathTime.HasValue)</span><span style=”color: #008000;”&gt;//</span><span style=”color: #008000;”&gt; return (DeathTime.Value – BirthTime).Days / 365;</span><span style=”color: #008000;”&gt;//</span><span style=”color: #008000;”&gt; else</span><span style=”color: #008000;”&gt;//</span><span style=”color: #008000;”&gt; return (DateTime.<a href=”https://www.jb51.cc/tag/Now/” target=”_blank” class=”keywords”>Now</a> – BirthTime).Days / 365;</span><span style=”color: #008000;”&gt;//</span><span style=”color: #008000;”&gt; }</span><span style=”color: #008000;”&gt;//</span><span style=”color: #008000;”&gt;}</span><span style=”color: #0000ff;”&gt;public</span> <span style=”color: #0000ff;”&gt;static</span> <span style=”color: #0000ff;”&gt;class</span><span style=”color: #000000;”&gt; ExtensionClass{ </span><span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<summary></span> <span style=”color: #808080;”&gt;///</span><span style=”color: #008000;”&gt; 按条件<a href=”https://www.jb51.cc/tag/chaxun/” target=”_blank” class=”keywords”>查询</a> </span><span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;</summary></span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<typeparam name=”T”&gt;</typeparam></span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<param name=”list”&gt;@H_<a href=”https://www.jb51.cc/tag/502/” target=”_blank” class=”keywords”>502</a>_212@</span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<param name=”func”&gt;@H_<a href=”https://www.jb51.cc/tag/502/” target=”_blank” class=”keywords”>502</a>_212@</span> <span style=”color: #808080;”&gt;///</span> <span style=”color: #808080;”&gt;<returns></returns></span> <span style=”color: #0000ff;”&gt;public</span> <span style=”color: #0000ff;”&gt;static</span> IList<T> MyWhere<T>(<span style=”color: #0000ff;”&gt;this</span> IList<T> list,DateTime><span style=”color: #000000;”&gt; func) { </span><span style=”color: #0000ff;”&gt;if</span> (list.Count() <= <span style=”color: #800080;”&gt;1</span><span style=”color: #000000;”&gt;) </span><span style=”color: #0000ff;”&gt;return</span><span style=”color: #000000;”&gt; list; </span><span style=”color: #0000ff;”&gt;for</span> (<span style=”color: #0000ff;”&gt;int</span> i = <span style=”color: #800080;”&gt;0</span>; i < list.Count(); i++<span style=”color: #000000;”&gt;) { </span><span style=”color: #0000ff;”&gt;for</span> (<span style=”color: #0000ff;”&gt;int</span> j = <span style=”color: #800080;”&gt;1</span>; j < list.Count() – i; j++<span style=”color: #000000;”&gt;) { </span><span style=”color: #0000ff;”&gt;var</span> item1 = list[j – <span style=”color: #800080;”&gt;1</span><span style=”color: #000000;”&gt;]; </span><span style=”color: #0000ff;”&gt;var</span> item2 =<span style=”color: #000000;”&gt; list[j]; </span><span style=”color: #0000ff;”&gt;if</span> ((func(item1) – func(item2)).Ticks < <span style=”color: #800080;”&gt;0</span><span style=”color: #000000;”&gt;) { list[j </span>- <span style=”color: #800080;”&gt;1</span>] =<span style=”color: #000000;”&gt; item2; list[j] </span>=<span style=”color: #000000;”&gt; item1; } } } </span><span style=”color: #0000ff;”&gt;return</span><span style=”color: #000000;”&gt; list; } </span><span style=”color: #0000ff;”&gt;public</span> <span style=”color: #0000ff;”&gt;static</span> <span style=”color: #0000ff;”&gt;int</span><span style=”color: #000000;”&gt; GetAge2(Person person) { </span><span style=”color: #0000ff;”&gt;if</span><span style=”color: #000000;”&gt; (person.DeathTime.HasValue) </span><span style=”color: #0000ff;”&gt;return</span> (person.DeathTime.Value – person.BirthTime).Days / <span style=”color: #800080;”&gt;365</span><span style=”color: #000000;”&gt;; </span><span style=”color: #0000ff;”&gt;else</span> <span style=”color: #0000ff;”&gt;return</span> (DateTime.<a href=”https://www.jb51.cc/tag/Now/” target=”_blank” class=”keywords”>Now</a> – person.BirthTime).Days / <span style=”color: #800080;”&gt;365</span><span style=”color: #000000;”&gt;; } </span><span style=”color: #0000ff;”&gt;public</span> <span style=”color: #0000ff;”&gt;static</span> <span style=”color: #0000ff;”&gt;int</span> GetAge(<span style=”color: #0000ff;”&gt;this</span><span style=”color: #000000;”&gt; Person person) { </span><span style=”color: #0000ff;”&gt;if</span><span style=”color: #000000;”&gt; (person.DeathTime.HasValue) </span><span style=”color: #0000ff;”&gt;return</span> (person.DeathTime.Value – person.BirthTime).Days / <span style=”color: #800080;”&gt;365</span><span style=”color: #000000;”&gt;; </span><span style=”color: #0000ff;”&gt;else</span> <span style=”color: #0000ff;”&gt;return</span> (DateTime.<a href=”https://www.jb51.cc/tag/Now/” target=”_blank” class=”keywords”>Now</a> – person.BirthTime).Days / <span style=”color: #800080;”&gt;365</span><span style=”color: #000000;”&gt;; } </span><span style=”color: #0000ff;”&gt;public</span> <span style=”color: #0000ff;”&gt;static</span> <span style=”color: #0000ff;”&gt;bool</span> IsNullOrEmpty(<span style=”color: #0000ff;”&gt;this</span> <span style=”color: #0000ff;”&gt;string</span><span style=”color: #000000;”&gt; str) { </span><span style=”color: #0000ff;”&gt;return</span> <span style=”color: #0000ff;”&gt;string</span><span style=”color: #000000;”&gt;.IsNullOrEmpty(str); }}

}

本文以同步至《》