C# 只保留字符串中的数值？
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Keep only numeric value from a string?
提问by meda
I have some strings like this
我有一些这样的字符串
string phoneNumber = "(914) 395-1430";
I would like to strip out the parethenses and the dash, in other word just keep the numeric values.
我想去掉括号和破折号，换句话说，只保留数值。
So the output could look like this
所以输出看起来像这样
9143951430
How do I get the desired output ?
如何获得所需的输出？
采纳答案by Nicholas Carey
You do any of the following:
您执行以下任一操作：
Use regular expressions. You can use a regular expression with either
A negative character class that defines the characters that are what you don't want (those characters other than decimal digits):
private static readonly Regex rxNonDigits = new Regex( @"[^\d]+");In which case, you can do take either of these approaches:
// simply replace the offending substrings with an empty string private string CleanStringOfNonDigits_V1( string s ) { if ( string.IsNullOrEmpty(s) ) return s ; string cleaned = rxNonDigits.Replace(s, "") ; return cleaned ; } // split the string into an array of good substrings // using the bad substrings as the delimiter. Then use // String.Join() to splice things back together. private string CleanStringOfNonDigits_V2( string s ) { if (string.IsNullOrEmpty(s)) return s; string cleaned = String.Join( rxNonDigits.Split(s) ); return cleaned ; }a positive character set that defines what you do want (decimal digits):
private static Regex rxDigits = new Regex( @"[\d]+") ;In which case you can do something like this:
private string CleanStringOfNonDigits_V3( string s ) { if ( string.IsNullOrEmpty(s) ) return s ; StringBuilder sb = new StringBuilder() ; for ( Match m = rxDigits.Match(s) ; m.Success ; m = m.NextMatch() ) { sb.Append(m.Value) ; } string cleaned = sb.ToString() ; return cleaned ; }
You're not required to use a regular expression, either.
You could use LINQ directly, since a string is an
IEnumerable<char>:private string CleanStringOfNonDigits_V4( string s ) { if ( string.IsNullOrEmpty(s) ) return s; string cleaned = new string( s.Where( char.IsDigit ).ToArray() ) ; return cleaned; }If you're only dealing with western alphabets where the only decimal digits you'll see are ASCII, skipping
char.IsDigitwill likely buy you a little performance:private string CleanStringOfNonDigits_V5( string s ) { if (string.IsNullOrEmpty(s)) return s; string cleaned = new string(s.Where( c => c-'0' < 10 ).ToArray() ) ; return cleaned; }
Finally, you can simply iterate over the string, chucking the digits you don't want, like this:
private string CleanStringOfNonDigits_V6( string s ) { if (string.IsNullOrEmpty(s)) return s; StringBuilder sb = new StringBuilder(s.Length) ; for (int i = 0; i < s.Length; ++i) { char c = s[i]; if ( c < '0' ) continue ; if ( c > '9' ) continue ; sb.Append(s[i]); } string cleaned = sb.ToString(); return cleaned; }Or this:
private string CleanStringOfNonDigits_V7(string s) { if (string.IsNullOrEmpty(s)) return s; StringBuilder sb = new StringBuilder(s); int j = 0 ; int i = 0 ; while ( i < sb.Length ) { bool isDigit = char.IsDigit( sb[i] ) ; if ( isDigit ) { sb[j++] = sb[i++]; } else { ++i ; } } sb.Length = j; string cleaned = sb.ToString(); return cleaned; }
使用正则表达式。您可以使用正则表达式
一个负字符类，用于定义您不想要的字符（十进制数字以外的字符）：
private static readonly Regex rxNonDigits = new Regex( @"[^\d]+");在这种情况下，您可以采取以下任一方法：
// simply replace the offending substrings with an empty string private string CleanStringOfNonDigits_V1( string s ) { if ( string.IsNullOrEmpty(s) ) return s ; string cleaned = rxNonDigits.Replace(s, "") ; return cleaned ; } // split the string into an array of good substrings // using the bad substrings as the delimiter. Then use // String.Join() to splice things back together. private string CleanStringOfNonDigits_V2( string s ) { if (string.IsNullOrEmpty(s)) return s; string cleaned = String.Join( rxNonDigits.Split(s) ); return cleaned ; }定义您想要的内容的正字符集（十进制数字）：
private static Regex rxDigits = new Regex( @"[\d]+") ;在这种情况下，您可以执行以下操作：
private string CleanStringOfNonDigits_V3( string s ) { if ( string.IsNullOrEmpty(s) ) return s ; StringBuilder sb = new StringBuilder() ; for ( Match m = rxDigits.Match(s) ; m.Success ; m = m.NextMatch() ) { sb.Append(m.Value) ; } string cleaned = sb.ToString() ; return cleaned ; }
您也不需要使用正则表达式。
您可以直接使用 LINQ，因为字符串是一个
IEnumerable<char>：private string CleanStringOfNonDigits_V4( string s ) { if ( string.IsNullOrEmpty(s) ) return s; string cleaned = new string( s.Where( char.IsDigit ).ToArray() ) ; return cleaned; }如果您只处理西方字母，其中您将看到的唯一十进制数字是 ASCII，那么跳过
char.IsDigit可能会给您带来一点性能：private string CleanStringOfNonDigits_V5( string s ) { if (string.IsNullOrEmpty(s)) return s; string cleaned = new string(s.Where( c => c-'0' < 10 ).ToArray() ) ; return cleaned; }
最后，您可以简单地遍历字符串，删除您不想要的数字，如下所示：
private string CleanStringOfNonDigits_V6( string s ) { if (string.IsNullOrEmpty(s)) return s; StringBuilder sb = new StringBuilder(s.Length) ; for (int i = 0; i < s.Length; ++i) { char c = s[i]; if ( c < '0' ) continue ; if ( c > '9' ) continue ; sb.Append(s[i]); } string cleaned = sb.ToString(); return cleaned; }或这个：
private string CleanStringOfNonDigits_V7(string s) { if (string.IsNullOrEmpty(s)) return s; StringBuilder sb = new StringBuilder(s); int j = 0 ; int i = 0 ; while ( i < sb.Length ) { bool isDigit = char.IsDigit( sb[i] ) ; if ( isDigit ) { sb[j++] = sb[i++]; } else { ++i ; } } sb.Length = j; string cleaned = sb.ToString(); return cleaned; }
From a standpoint of clarity and cleanness of code, the version 1 is what you want. It's hard to beat a one liner.
从代码的清晰度和清洁度的角度来看，版本 1 就是您想要的。很难击败单班轮。
If performance matters, my suspicion is that the version 7, the last version, is the winner. It creates one temporary — a StringBuilder()and does the transformation in-place within the StringBuilder's in-place buffer.
如果性能很重要，我怀疑版本 7，即最后一个版本，是赢家。它创建了一个临时的 — aStringBuilder()并在 StringBuilder 的就地缓冲区中进行就地转换。
The other options all do more work.
其他选项都做更多的工作。
回答by COLD TOLD
use reg expression
使用reg表达式
string result = Regex.Replace(phoneNumber, @"[^\d]", "");
回答by L.B
string phoneNumber = "(914) 395-1430";
var numbers = String.Join("", phoneNumber.Where(char.IsDigit));
回答by Darka
He means everything @gleng
他意味着一切@glen
Regex rgx = new Regex(@"\D");
str = rgx.Replace(str, "");
回答by BRAHIM Kamel
try something like this
尝试这样的事情
return new String(input.Where(Char.IsDigit).ToArray());
回答by Guffa
Instead of a regular expression, you can use a LINQ method:
您可以使用 LINQ 方法代替正则表达式：
phoneNumber = String.Concat(phoneNumber.Where(c => c >= '0' && c <= '9'));
or:
或者：
phoneNumber = String.Concat(phoneNumber.Where(Char.IsDigit));
