blocks|key|824209|text|除了连接运算符之外，String.Format还添加了许多选项，包括指定添加到字符串中的每个项目的特定格式的能力。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|824210|有关可能的详细信息，我建议阅读MSDN上标题为Composite+Formatting的部分。它解释了String.Format+(以及xxx.WriteLine和其他支持复合格式化的方法)相对于普通连接运算符的优势。|824211|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/fht0f5be.aspx|1|http://msdn.microsoft.com/en-us/library/txafckwd.aspx^0|A|D|A|D|0|0|1F|D|1W|D|N|K|1|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@$9|U|A|V|1|W]]|E|$]]|$1|F|3|G|5|6|7|X|8|@$9|Y|A|Z|B|C]|$9|10|A|11|B|C]]|D|@$9|12|A|13|1|14]]|E|$]]|$1|H|3|-4|5|6|7|15|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]|P|$5|K|L|M|E|$N|Q]]]]

<a href="http://msdn.microsoft.com/en-us/library/fht0f5be.aspx" rel="nofollow noreferrer"><code>String.Format</code></a> adds many options in addition to the concatenation operators, including the ability to specify the specific format of each item added into the string.

For details on what is possible, I'd recommend reading the section on MSDN titled <a href="http://msdn.microsoft.com/en-us/library/txafckwd.aspx" rel="nofollow noreferrer">Composite Formatting</a>. It explains the advantage of <code>String.Format</code> (as well as <code>xxx.WriteLine</code> and other methods that support composite formatting) over normal concatenation operators.

blocks|key|824265|text|首先，我发现|type|unstyled|depth|inlineStyleRanges|entityRanges|data|824266|string+s+=+String.Format(
++++"Your+order+{0}+will+be+delivered+on+{1:yyyy-MM-dd}.+Your+total+cost+is+{2:C}.",
++++orderNumber,
++++orderDeliveryDate,
++++orderCost
);|code-block|syntax|javascript|824267|更易于读取、写入和维护|824268|string+s+=+"Your+order+"+%2B
+++++++++++orderNumber.ToString()+%2B
+++++++++++"+will+be+delivered+on+"+%2B
+++++++++++orderDeliveryDate.ToString("yyyy-MM-dd")+%2B
+++++++++++"."+%2B
+++++++++++"Your+total+cost+is+"+%2B
+++++++++++orderCost.ToString("C")+%2B+
+++++++++++".";|824269|看看以下代码的可维护性有多高|824270|string+s+=+String.Format(
++++"Year+=+{0:yyyy},+Month+=+{0:MM},+Day+=+{0:dd}",
++++date
);|824271|在另一种情况下，您必须重复date三次。|offset|length|style|CODE|824272|其次，String.Format提供的格式说明符在字符串输出方面为您提供了极大的灵活性，与仅使用普通的旧连接相比，这种方式更易于读取、写入和维护。此外，使用String.Format可以更容易地解决文化问题。|824273|第三，当性能确实很重要时，String.Format将优于连接。在幕后，它使用StringBuilder并避免使用Schlemiel+the+Painter+problem。|824274|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Schlemiel_the_Painter's_algorithm^0|0|0|0|0|0|0|D|4|0|3|D|26|D|0|D|D|13|D|1L|T|0|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|17|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|18|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|19|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|1A|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|1B|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|1C|8|@$Q|1D|R|1E|S|T]]|9|@]|A|$]]|$1|U|3|V|5|6|7|1F|8|@$Q|1G|R|1H|S|T]|$Q|1I|R|1J|S|T]]|9|@]|A|$]]|$1|W|3|X|5|6|7|1K|8|@$Q|1L|R|1M|S|T]|$Q|1N|R|1O|S|T]]|9|@$Q|1P|R|1Q|1|1R]]|A|$]]|$1|Y|3|-4|5|6|7|1S|8|@]|9|@]|A|$]]]|Z|$10|$5|11|12|13|A|$14|15]]]]

First, I find

<pre><code>string s = String.Format(
 "Your order {0} will be delivered on {1:yyyy-MM-dd}. Your total cost is {2:C}.",
 orderNumber,
 orderDeliveryDate,
 orderCost
);
</code></pre>

far easier to read, write and maintain than

<pre><code>string s = "Your order " +
 orderNumber.ToString() +
 " will be delivered on " +
 orderDeliveryDate.ToString("yyyy-MM-dd") +
 "." +
 "Your total cost is " +
 orderCost.ToString("C") + 
 ".";
</code></pre>

Look how much more maintainable the following is

<pre><code>string s = String.Format(
 "Year = {0:yyyy}, Month = {0:MM}, Day = {0:dd}",
 date
);
</code></pre>

over the alternative where you'd have to repeat <code>date</code> three times.

Second, the format specifiers that <code>String.Format</code> provides give you great flexibility over the output of the string in a way that is easier to read, write and maintain than just using plain old concatenation. Additionally, it's easier to get culture concerns right with <code>String.Format</code>.

Third, when performance does matter, <code>String.Format</code> will outperform concatenation. Behind the scenes it uses a <code>StringBuilder</code> and avoids the <a href="http://en.wikipedia.org/wiki/Schlemiel_the_Painter&#39;s_algorithm" rel="noreferrer">Schlemiel the Painter problem</a>.

blocks|key|824317|text|this+question中有一些关于性能方面的有趣内容|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|824318|但是，我个人仍然推荐使用string.Format，除非出于可读性的原因，性能非常重要。|style|CODE|824319|string.Format("{0}:+{1}",+key,+value);|code-block|syntax|javascript|824320|的可读性比|824321|key+%2B+":+"+%2B+value|824322|例如。还提供了良好的关注点分离。意味着你可以拥有|824323|string.Format(GetConfigValue("KeyValueFormat"),+key,+value);|824324|然后，将键值格式从"{0}:+{1}"更改为"{0}+-+{1}"将成为配置更改，而不是代码更改。|824325|string.Format还内置了一系列格式设置，整数、日期格式化等。|824326|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/21078/whats-the-best-string-concatenation-method-using-c^0|0|D|0|0|C|D|0|0|0|0|0|0|9|A|M|B|0|0|D|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@$A|17|B|18|1|19]]|C|$]]|$1|D|3|E|5|6|7|1A|8|@$A|1B|B|1C|F|G]]|9|@]|C|$]]|$1|H|3|I|5|J|7|1D|8|@]|9|@]|C|$K|L]]|$1|M|3|N|5|6|7|1E|8|@]|9|@]|C|$]]|$1|O|3|P|5|J|7|1F|8|@]|9|@]|C|$K|L]]|$1|Q|3|R|5|6|7|1G|8|@]|9|@]|C|$]]|$1|S|3|T|5|J|7|1H|8|@]|9|@]|C|$K|L]]|$1|U|3|V|5|6|7|1I|8|@$A|1J|B|1K|F|G]|$A|1L|B|1M|F|G]]|9|@]|C|$]]|$1|W|3|X|5|6|7|1N|8|@$A|1O|B|1P|F|G]]|9|@]|C|$]]|$1|Y|3|-4|5|6|7|1Q|8|@]|9|@]|C|$]]]|Z|$10|$5|11|12|13|C|$14|15]]]]

There's interesting stuff on the performance aspects in <a href="https://stackoverflow.com/questions/21078/whats-the-best-string-concatenation-method-using-c">this question</a>

However I personally would still recommend <code>string.Format</code> unless performance is critical for readability reasons.

<pre><code>string.Format("{0}: {1}", key, value);
</code></pre>

Is more readable than

<pre><code>key + ": " + value
</code></pre>

For instance. Also provides a nice separation of concerns. Means you can have

<pre><code>string.Format(GetConfigValue("KeyValueFormat"), key, value);
</code></pre>

And then changing your key value format from <code>"{0}: {1}"</code> to <code>"{0} - {1}"</code> becomes a config change rather than a code change.

<code>string.Format</code> also has a bunch of format provision built into it, integers, date formatting, etc.

blocks|key|1039288|text|除了更容易阅读和添加更多的运算符之外，如果您的应用程序是国际化的，这也是有益的。很多时候，变量是数字或关键字，它们在不同的语言中会有不同的顺序。通过使用String.Format，您的代码可以保持不变，而不同的字符串将进入资源文件。因此，代码最终会是|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1039289|String.Format(resource.GetString("MyResourceString"),+str1,+str2,+str3);|code-block|syntax|javascript|1039290|而您的资源字符串最终是|1039291|中文："blah+blah+{0}+blah+blah+{1}+blah+{2}"|offset|length|style|CODE|1039292|俄语："{0}+blet+blet+blet+{2}+blet+{1}"|1039293|俄语可能对如何处理事物有不同的规则，因此顺序不同或句子结构也不同。|1039294|entityMap^0|0|0|0|3|12|0|3|X|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|X|8|@$K|Y|L|Z|M|N]]|9|@]|A|$]]|$1|O|3|P|5|6|7|10|8|@$K|11|L|12|M|N]]|9|@]|A|$]]|$1|Q|3|R|5|6|7|13|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|T|$]]

Besides being a bit easier to read and adding a few more operators, it's also beneficial if your application is internationalized. A lot of times the variables are numbers or key words which will be in a different order for different languages. By using String.Format, your code can remain unchanged while different strings will go into resource files. So, the code would end up being

<pre><code>String.Format(resource.GetString("MyResourceString"), str1, str2, str3);
</code></pre>

While your resource strings end up being 

English: <code>"blah blah {0} blah blah {1} blah {2}"</code>

Russian: <code>"{0} blet blet blet {2} blet {1}"</code>

Where Russian may have different rules on how things get addressed so the order is different or sentence structure is different.

blocks|key|1039332|text|不推荐像'string+%2B"Value"%2B+string'这样编写字符串的一个原因是由于本地化的原因。在发生本地化的情况下，我们希望本地化的字符串被正确格式化，这可能与正在编码的语言非常不同。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1039333|例如，我们需要以不同的语言显示以下错误：|1039334|MessageBox.Show(String.Format(ErrorManager.GetError("PIDV001").Description,+proposalvalue.ProposalSource)|code-block|syntax|javascript|1039335|哪里|1039336|'ErrorCollector.GetError("ERR001").ErrorDescription'返回一个类似于"Your+ID+{0}+is+not+valid"的字符串。此消息必须以多种语言进行本地化。在这种情况下，我们不能在C#中使用%2B。我们得跟着string.format走。|1039337|entityMap^0|4|P|0|0|0|0|0|1G|1N|Q|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|V|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|W|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|X|8|@]|D|@]|E|$]]|$1|O|3|P|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|R|$]]

One reason it is not preferable to write the string like <code>'string +"Value"+ string'</code> is because of Localization. In cases where localization is occurring we want the localized string to be correctly formatted, which could be very different from the language being coded in. 

For example we need to show the following error in different languages:

<pre><code>MessageBox.Show(String.Format(ErrorManager.GetError("PIDV001").Description, proposalvalue.ProposalSource)
</code></pre>

where 

<code>'ErrorCollector.GetError("ERR001").ErrorDescription'</code> returns a string like <code>"Your ID {0} is not valid"</code>. This message must be localized in many languages. In that case we can't use + in C#. We need to follow string.format.

Why would anyone use <code>String.Format</code> in C# and VB .NET as opposed to the concatenation operators (<code>&amp;</code> in VB, and <code>+</code> in C#)?

What is the main difference? Why are everyone so interested in using <code>String.Format</code>? I am very curious.

Why use String.Format?

为什么有人会在C#和VB .NET中使用String.Format，而不是使用连接运算符( VB中的&和C#中的+ )？主要区别是什么？为什么每个人都对使用String.Format如此感兴趣？我很好奇。

问为什么使用String.Format？
EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问为什么使用String.Format？EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问为什么使用String.Format？
EN