blocks|key|941478|text|您可以组合使用Substring和IndexOf。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|941479|var+s+=+"Hello+World";
var+firstWord+=+s.Substring(0,s.IndexOf("+"));|code-block|syntax|javascript|941480|但是，如果输入字符串只有一个单词，这将不会给出预期的单词，因此需要一个特殊情况。|941481|var+s+=+"Hello";
var+firstWord+=+s.IndexOf("+")+>+-1+
++++++++++++++++++?+s.Substring(0,s.IndexOf("+"))
++++++++++++++++++:+s;|941482|entityMap^0|7|9|H|7|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|P|$]]

You can use a combination of <code>Substring</code> and <code>IndexOf</code>.

<pre><code>var s = "Hello World";
var firstWord = s.Substring(0,s.IndexOf(" "));
</code></pre>

However, this will not give the expected word if the input string only has one word, so a special case is needed.

<pre><code>var s = "Hello";
var firstWord = s.IndexOf(" ") &gt; -1 
 ? s.Substring(0,s.IndexOf(" "))
 : s;
</code></pre>

blocks|key|1155793|text|您可以尝试：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1155794|string+s+=+"Hello+World";
string+firstWord+=+s.Split('+').First();|code-block|syntax|javascript|1155795|Ohad+Schneider's注释是正确的，所以您可以简单地请求First()元素，因为总会有至少一个元素。|offset|length|style|CODE|1155796|有关使用First()还是FirstOrDefault()的更多信息，您可以了解更多here|1155797|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/users/67824/ohad-schneider|1|https://stackoverflow.com/questions/1024559/when-to-use-first-and-when-to-use-firstordefault-with-linq^0|0|0|X|7|0|G|0|0|4|7|D|G|16|4|1|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|10|8|@$I|11|J|12|K|L]]|9|@$I|13|J|14|1|15]]|A|$]]|$1|M|3|N|5|6|7|16|8|@$I|17|J|18|K|L]|$I|19|J|1A|K|L]]|9|@$I|1B|J|1C|1|1D]]|A|$]]|$1|O|3|-4|5|6|7|1E|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|V]]|W|$5|R|S|T|A|$U|X]]]]

You can try:

<pre><code>string s = "Hello World";
string firstWord = s.Split(' ').First();
</code></pre>

<a href="https://stackoverflow.com/users/67824/ohad-schneider">Ohad Schneider's</a> comment is right, so you can simply ask for the <code>First()</code> element as there will always be at least one element.

For further info on whether to use <code>First()</code> or <code>FirstOrDefault()</code> you can learn more <a href="https://stackoverflow.com/questions/1024559/when-to-use-first-and-when-to-use-firstordefault-with-linq">here</a>

blocks|key|1155757|text|一种方法是在字符串中查找空格，并使用空格的位置来获得第一个单词：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1155758|int+index+=+s.IndexOf('+');
if+(index+!=+-1)+{
++s+=+s.Substring(0,+index);
}|code-block|syntax|javascript|1155759|另一种方法是使用正则表达式来查找单词边界：|1155760|s+=+Regex.Match(s,+@"(.%2B?)\b").Groups[1].Value;|1155761|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

One way is to look for a space in the string, and use the position of the space to get the first word:

<pre><code>int index = s.IndexOf(' ');
if (index != -1) {
 s = s.Substring(0, index);
}
</code></pre>

Another way is to use a regular expression to look for a word boundary:

<pre><code>s = Regex.Match(s, @"(.+?)\b").Groups[1].Value;
</code></pre>

blocks|key|941658|text|如果您只想在空格上拆分，answer+of+Jamiec是最有效的。但是，为了方便起见，这里有另一个版本：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|941659|var++FirstWord+=+"Hello+World".Split(null,+StringSplitOptions.RemoveEmptyEntries)[0];|code-block|syntax|javascript|941660|另外，它还将识别all+kinds+of+exotic+whitespace+characters，并忽略多个连续的空格字符(实际上，它将从结果中删除前导/尾随空格)。|941661|注意，它也会将符号算作字母，所以如果你的字符串是Hello,+world!，它将返回Hello,。如果不需要，那么在第一个参数中传递一个分隔符字符数组。|style|CODE|941662|但是，如果你想让它在世界上的每一种语言中都是100%25万无一失的，那么它就会变得很难……|941663|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/3607310/left-string-function-in-c/3607316#3607316|1|http://msdn.microsoft.com/en-us/library/t809ektx.aspx^0|C|G|0|0|0|8|15|1|0|O|D|16|6|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@$A|11|B|12|1|13]]|C|$]]|$1|D|3|E|5|F|7|14|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|15|8|@]|9|@$A|16|B|17|1|18]]|C|$]]|$1|K|3|L|5|6|7|19|8|@$A|1A|B|1B|M|N]|$A|1C|B|1D|M|N]]|9|@]|C|$]]|$1|O|3|P|5|6|7|1E|8|@]|9|@]|C|$]]|$1|Q|3|-4|5|6|7|1F|8|@]|9|@]|C|$]]]|R|$S|$5|T|U|V|C|$W|X]]|Y|$5|T|U|V|C|$W|Z]]]]

The <a href="https://stackoverflow.com/questions/3607310/left-string-function-in-c/3607316#3607316">answer of Jamiec</a> is the most efficient if you want to split only on spaces. But, just for the sake of variety, here's another version:

<pre><code>var FirstWord = "Hello World".Split(null, StringSplitOptions.RemoveEmptyEntries)[0];
</code></pre>

As a bonus this will also recognize <a href="http://msdn.microsoft.com/en-us/library/t809ektx.aspx" rel="nofollow noreferrer">all kinds of exotic whitespace characters</a> and will ignore multiple consecutive whitespace characters (in effect it will trim the leading/trailing whitespace from the result).

Note that it will count symbols as letters too, so if your string is <code>Hello, world!</code>, it will return <code>Hello,</code>. If you don't need that, then pass an array of delimiter characters in the first parameter.

But if you want it to be 100% foolproof in every language of the world, then it's going to get tough...

blocks|key|941678|text|不知羞耻地从msdn站点被盗(http://msdn.microsoft.com/en-us/library/b873y76a.aspx)|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|941679|string+words+=+"This+is+a+list+of+words,+with:+a+bit+of+punctuation"+%2B
++++"\tand+a+tab+character.";

string+[]+split+=+words.Split(new+Char+[]+{'+',+',',+'.',+':',+'\t'+});

if(+split.Length+>+0+)
{
++++return+split[0];
}|code-block|syntax|javascript|941680|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/b873y76a.aspx^0|F|1H|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Shamelessly stolen from the msdn site (<a href="http://msdn.microsoft.com/en-us/library/b873y76a.aspx" rel="nofollow noreferrer">http://msdn.microsoft.com/en-us/library/b873y76a.aspx</a>)

<pre><code>string words = "This is a list of words, with: a bit of punctuation" +
 "\tand a tab character.";

string [] split = words.Split(new Char [] {' ', ',', '.', ':', '\t' });

if( split.Length &gt; 0 )
{
 return split[0];
}
</code></pre>

blocks|key|1155916|text|处理各种不同的空格字符、空字符串和单字符串。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1155917|private+static+string+FirstWord(string+text)
{
++++if+(text+==+null)+throw+new+ArgumentNullException("text");

++++var+builder+=+new+StringBuilder();

++++for+(int+index+=+0;+index+<+text.Length;+index+%2B=+1)
++++{
++++++++char+ch+=+text[index];
++++++++if+(Char.IsWhiteSpace(ch))+break;

++++++++builder.Append(ch);
++++}

++++return+builder.ToString();
}|code-block|syntax|javascript|1155918|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|$]]

Handles the various different whitespace characters, empty string and string of single word.

<pre><code>private static string FirstWord(string text)
{
 if (text == null) throw new ArgumentNullException("text");

 var builder = new StringBuilder();

 for (int index = 0; index &lt; text.Length; index += 1)
 {
 char ch = text[index];
 if (Char.IsWhiteSpace(ch)) break;

 builder.Append(ch);
 }

 return builder.ToString();
}</code></pre>

blocks|key|1155707|text|string+words+=+"hello+world";
string+[]+split+=+words.Split(new+Char+[]+{'+'});
if(split.Length+>0){
+string+first+=+split[0];
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1155708|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>string words = "hello world";
string [] split = words.Split(new Char [] {' '});
if(split.Length &gt;0){
 string first = split[0];
}
</code></pre>

blocks|key|1155952|text|我在我的代码中使用了这个函数。它提供了大写第一个单词或每个单词的选项。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1155953|++++++++public+static+string+FirstCharToUpper(string+text,+bool+firstWordOnly+=+true)
++++{
++++++++try
++++++++{
++++++++++++if+(string.IsNullOrEmpty(text))
++++++++++++{
++++++++++++++++return+text;
++++++++++++}
++++++++++++else
++++++++++++{
++++++++++++++++if+(firstWordOnly)
++++++++++++++++{
++++++++++++++++++++string[]+words+=+text.Split('+');
++++++++++++++++++++string+firstWord+=+words.First();
++++++++++++++++++++firstWord+=+System.Globalization.CultureInfo.CurrentCulture.TextInfo.ToTitleCase(firstWord.ToLower());
++++++++++++++++++++words[0]+=+firstWord;
++++++++++++++++++++return+string.Join("+",+words);
++++++++++++++++}
++++++++++++++++else
++++++++++++++++{
++++++++++++++++++++return+System.Globalization.CultureInfo.CurrentCulture.TextInfo.ToTitleCase(text.ToLower());
++++++++++++++++}
++++++++++++}
++++++++}+catch+(Exception+ex)
++++++++{
++++++++++++Log.Exc(ex);
++++++++++++return+text;
++++++++}
++++}|code-block|syntax|javascript|1155954|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|$]]

I used this function in my code. It provides an option to either uppercase the first word or every single word. 

<pre><code> public static string FirstCharToUpper(string text, bool firstWordOnly = true)
 {
 try
 {
 if (string.IsNullOrEmpty(text))
 {
 return text;
 }
 else
 {
 if (firstWordOnly)
 {
 string[] words = text.Split(' ');
 string firstWord = words.First();
 firstWord = System.Globalization.CultureInfo.CurrentCulture.TextInfo.ToTitleCase(firstWord.ToLower());
 words[0] = firstWord;
 return string.Join(" ", words);
 }
 else
 {
 return System.Globalization.CultureInfo.CurrentCulture.TextInfo.ToTitleCase(text.ToLower());
 }
 }
 } catch (Exception ex)
 {
 Log.Exc(ex);
 return text;
 }
 }
</code></pre>

What's the best way to return the first word of a string in C#?

Basically if the string is <code>"hello world"</code>, I need to get <code>"hello"</code>.

Thanks

left string function in C#

在C#中返回字符串第一个单词的最佳方法是什么？基本上，如果字符串是"hello world"，我需要获取"hello"。谢谢

问C#中的左字符串函数
EN

回答 8

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