blocks|key|2948576|text|它们是lambda函数的参数。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2948577|编译器从上下文中推断出它们的类型，但允许编写更长的(更具信息性的)形式：|2948578|+textBox.TextChanged+%2B=+(object+s,+EventArgs+e)+=>+{+this.Foo();+};|code-block|syntax|javascript|2948579|在这种表示法中，更容易看出它们是方法参数。|2948580|在=>的另一边是方法体。|offset|length|style|CODE|2948581|2948582|回应评论：|2948583|2948584|现在有没有办法用更简单的C#语法重写相同的lambda表达式？|blockquote|2948585|2948586|2948587|是的，你总是可以使用经典的符号。虽然这可能不是“更好的”，甚至“更简单”，但当你学习这一点时，它更容易理解。|2948588|//+The+setup+method
void+MyMethod()
{
+++//textBox.TextChanged+%2B=+new+Eventhandler(MyTextChangedHandler);++//+C#1+and+later
+++textBox.TextChanged+%2B=+MyTextChangedHandler;++++++++++++++++++++++//+C#2+and+later
}

//+The+subscribed+method.+The+lambda+is+an+inline+version+of+this.+
private+void+MyTextChangedHandler(object+s,+EventArgs+e)
{+
+++this.Foo();+
}|2948589|entityMap^0|0|0|0|0|1|2|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|15|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|16|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|17|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|18|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|19|8|@$M|1A|N|1B|O|P]]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|1C|8|@]|9|@]|A|$]]|$1|R|3|S|5|6|7|1D|8|@]|9|@]|A|$]]|$1|T|3|-4|5|6|7|1E|8|@]|9|@]|A|$]]|$1|U|3|V|5|W|7|1F|8|@]|9|@]|A|$]]|$1|X|3|-4|5|6|7|1G|8|@]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|1H|8|@]|9|@]|A|$]]|$1|Z|3|10|5|6|7|1I|8|@]|9|@]|A|$]]|$1|11|3|12|5|F|7|1J|8|@]|9|@]|A|$G|H]]|$1|13|3|-4|5|6|7|1K|8|@]|9|@]|A|$]]]|14|$]]

They are the parameters of the lambda-function.

The compiler infers their types from the context, but it is allowed to write a longer (more informative) form:

<pre><code> textBox.TextChanged += (object s, EventArgs e) =&gt; { this.Foo(); };
</code></pre>

In this notation it is easier to see that they are method parameters. 
On the other side of <code>=&gt;</code> is the method body. 

<hr>

In response to comment:

<blockquote>
 Now is there a way to also rewrite the same lambda expression I have in a simpler C# syntax?
</blockquote>

Yes, you can always use the classic notation. And while that may not be 'better' or even 'simpler' it is easier to understand when you are learning this.

<pre><code>// The setup method
void MyMethod()
{
 //textBox.TextChanged += new Eventhandler(MyTextChangedHandler); // C#1 and later
 textBox.TextChanged += MyTextChangedHandler; // C#2 and later
}

// The subscribed method. The lambda is an inline version of this. 
private void MyTextChangedHandler(object s, EventArgs e)
{ 
 this.Foo(); 
}
</code></pre>

blocks|key|2534650|text|s是源对象，而e是应该是EventArgs对象或从EventArgs类扩展的对象，您必须读取lambda+expression|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2534651|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/bb397687.aspx^0|0|1|7|1|C|9|1A|H|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|C]|$9|S|A|T|B|C]]|D|@$9|U|A|V|1|W]]|E|$]]|$1|F|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

<code>s</code> is source object and <code>e</code> is object that should be <code>EventArgs</code> object or extended from EventArgs class, You have to read <a href="http://msdn.microsoft.com/en-us/library/bb397687.aspx" rel="nofollow">lambda expression</a>

blocks|key|2534773|text|是用作委托快捷方式的lamda表达式。TextChanded需要一个带两个参数的委托，object+sender,+EventArgs+e。lambda版本用占位符标记这些参数，即s=sender,+e=eventargs。只是一种语法糖，因为在幕后它会转换为：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2534774|textBox.TextChanged+%2B=+new+EventHandler(delegate+(Object+s,+EventArgs+e)+{

++++++++++++});|code-block|syntax|javascript|2534775|entityMap^0|17|Q|2I|L|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

Is a lamda expression used as a shortcut for a delegate.
TextChanded expect a delegate taking two arguments, <code>object sender, EventArgs e</code>. The lambda version mark these arguments with placeholders, that is <code>s=sender, e=eventargs</code>. Is just a syntactic sugar since behind the scene it converts to:

<pre><code>textBox.TextChanged += new EventHandler(delegate (Object s, EventArgs e) {

 });
</code></pre>

blocks|key|4677448|text|您要查找的主题名为expression+lambdas。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|4677449|s和e是匿名函数的参数名称，其主体在=>之后指示。|style|CODE|4677450|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/bb397687.aspx^0|9|I|0|0|0|1|2|1|I|2|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]]|C|$]]|$1|D|3|E|5|6|7|T|8|@$A|U|B|V|F|G]|$A|W|B|X|F|G]|$A|Y|B|Z|F|G]]|9|@]|C|$]]|$1|H|3|-4|5|6|7|10|8|@]|9|@]|C|$]]]|I|$J|$5|K|L|M|C|$N|O]]]]

The topic you are looking for is called <a href="http://msdn.microsoft.com/en-us/library/bb397687.aspx" rel="nofollow">expression lambdas</a>.

<code>s</code> and <code>e</code> are names of parameters of an anonymous function whose body is indicated after the <code>=&gt;</code>.

blocks|key|4587543|text|S通常是发送者(调用事件的对象)，e是事件参数。这个stackoverflow答案应该可以解释这个问题：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4587544|Weak+event+handler+model+for+use+with+lambdas|offset|length|4587545|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/1747235/weak-event-handler-model-for-use-with-lambdas^0|0|0|19|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

S is usually going to be the sender (object that invoked the event) and e will be the event arguments. This stackoverflow answer should explain it:

<a href="https://stackoverflow.com/questions/1747235/weak-event-handler-model-for-use-with-lambdas">Weak event handler model for use with lambdas</a>

blocks|key|2949301|text|方法的参数。例如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2949302|protected+void+TextBox_TextChanged(Object+Sender,+EventArgs+Args)|code-block|syntax|javascript|2949303|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

parameters of method. for example :

<pre><code>protected void TextBox_TextChanged(Object Sender, EventArgs Args)
</code></pre>

blocks|key|2949340|text|这是一个lambda表达式。lambda表达式是编写方法(准确地说是委托)的一种非常简洁的方式。你可以像这样写一个方法|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2949341|private+void+TextBox_TextChanged(object+sender,+EventArgs+e)
{
++++this.Foo();
}|code-block|syntax|javascript|2949342|然后像这样添加处理程序|2949343|textBox.TextChanged+%2B=+TextBox_TextChanged;|2949344|它等同于|2949345|textBox.TextChanged+%2B=+(s,+e)+=>+this.Foo();|2949346|你也可以写成|2949347|textBox.TextChanged+%2B=+(object+s,+EventArgs+e)+=>+this.Foo();|2949348|但是参数的类型是由C#编译器自动推断出来的。s和e是参数，等同于TextBox_TextChanged方法的参数：object+sender,+EventArgs+e。它们可以用在=>后面的表达式中。|offset|length|style|CODE|2949349|textBox.TextChanged+%2B=+(s,+e)+=>+this.Foo(s,+e);|2949350|(假设Foo有一个相应的参数列表)这些参数的名称无关紧要。|2949351|2949352|更新|BOLD|2949353|如果必需的方法(或委托)需要返回值，则可以在lambda表达式中删除return关键字。给定此方法，|2949354|public+void+WriteValues(Func<double,+double>+f)
{
++++for+(int+i+=+0;+i+<=+10;+i%2B%2B)+{
++++++++Console.WriteLine("f({0})+=+{1}",+i,+f(i));
++++}
}|2949355|你可以打这些电话|2949356|WriteValues(x+=>+x+*+x);
WriteValues(x+=>+Math.Sin(x));
WriteValues(t+=>+Math.Exp(-t));|2949357|entityMap^0|0|0|0|0|0|0|0|0|M|1|O|1|W|J|1L|Q|2I|2|0|0|0|0|0|2|0|Y|6|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1G|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|1H|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|1I|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|1J|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|1K|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|1L|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|1M|8|@]|9|@]|A|$]]|$1|Q|3|R|5|D|7|1N|8|@]|9|@]|A|$E|F]]|$1|S|3|T|5|6|7|1O|8|@$U|1P|V|1Q|W|X]|$U|1R|V|1S|W|X]|$U|1T|V|1U|W|X]|$U|1V|V|1W|W|X]|$U|1X|V|1Y|W|X]]|9|@]|A|$]]|$1|Y|3|Z|5|D|7|1Z|8|@]|9|@]|A|$E|F]]|$1|10|3|11|5|6|7|20|8|@]|9|@]|A|$]]|$1|12|3|-4|5|6|7|21|8|@]|9|@]|A|$]]|$1|13|3|14|5|6|7|22|8|@$U|23|V|24|W|15]]|9|@]|A|$]]|$1|16|3|17|5|6|7|25|8|@$U|26|V|27|W|X]]|9|@]|A|$]]|$1|18|3|19|5|D|7|28|8|@]|9|@]|A|$E|F]]|$1|1A|3|1B|5|6|7|29|8|@]|9|@]|A|$]]|$1|1C|3|1D|5|D|7|2A|8|@]|9|@]|A|$E|F]]|$1|1E|3|-4|5|6|7|2B|8|@]|9|@]|A|$]]]|1F|$]]

This is a lambda expression. A lambda expression is a very concise way of writing a method (or a delegate to be precise). You could write a method like this

<pre><code>private void TextBox_TextChanged(object sender, EventArgs e)
{
 this.Foo();
}
</code></pre>

and then add the handler like this

<pre><code>textBox.TextChanged += TextBox_TextChanged;
</code></pre>

it would be equivalent to

<pre><code>textBox.TextChanged += (s, e) =&gt; this.Foo();
</code></pre>

You could also write

<pre><code>textBox.TextChanged += (object s, EventArgs e) =&gt; this.Foo();
</code></pre>

but the types of the arguments are inferred automatically by the C# compiler. <code>s</code> and <code>e</code> are the paramters and are equivalent to the paramters of the <code>TextBox_TextChanged</code> method: <code>object sender, EventArgs e</code>. They could be used in the expression following the <code>=&gt;</code>.

<pre><code>textBox.TextChanged += (s, e) =&gt; this.Foo(s, e);
</code></pre>

(assuming Foo has a corresponding parameter list)
The name of these parameters doesn't matter.

<hr>

UPDATE:

If the required method (or delegate) requires a return value, you can drop the <code>return</code> keyword in the lambda expression. Given this method

<pre><code>public void WriteValues(Func&lt;double, double&gt; f)
{
 for (int i = 0; i &lt;= 10; i++) {
 Console.WriteLine("f({0}) = {1}", i, f(i));
 }
}
</code></pre>

you can make these calls

<pre><code>WriteValues(x =&gt; x * x);
WriteValues(x =&gt; Math.Sin(x));
WriteValues(t =&gt; Math.Exp(-t));
</code></pre>

I see some code like this:

<pre><code>textBox.TextChanged += (s, e) =&gt; this.Foo();
</code></pre>

but I don't know what are "s" and "e" ? what is the topic I should study in C# for this line of code?

what are "s" and "e" in C# code syntax

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我看到一些代码如下所示：textBox.TextChanged += (s, e) => this.Foo();但我不知道"s“和"e”是什么？对于这行代码，我应该在C#中研究的主题是什么？

问C#代码语法中的"s“和"e”是什么
EN

回答 7

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