C# 从字符串中获取第一个数字
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Get first numbers from String
提问by Alaa Osta
How to get the first numbers from a string?
如何从字符串中获取第一个数字？
Example: I have "1567438absdg345"
示例：我有“1567438absdg345”
I only want to get "1567438" without "absdg345", I want it to be dynamic, get the first occurrence of Alphabet index and remove everything after it.
我只想得到没有“absdg345”的“1567438”，我希望它是动态的，获取第一次出现的字母索引并删除它之后的所有内容。
采纳答案by Guffa
You can use the TakeWhileextension methods to get characters from the string as long as they are digits:
您可以使用TakeWhile扩展方法从字符串中获取字符，只要它们是数字即可：
string input = "1567438absdg345";
string digits = new String(input.TakeWhile(Char.IsDigit).ToArray());
回答by TJHeuvel
You can loop through the string and test if the current character is numeric via Char.isDigit.
? ? ?
您可以遍历字符串并通过 测试当前字符是否为数字Char.isDigit。? ? ?
string str = "1567438absdg345";
string result = "";
for (int i = 0; i < str.Length; i++) // loop over the complete input
{
? ? if (Char.IsDigit(str[i])) //check if the current char is digit
? ? ? ? result += str[i];
? ? else
? ? ? ? break; //Stop the loop after the first character
}
回答by musefan
forget the regex, create this as a helper function somewhere...
忘记正则表达式，将其创建为某处的辅助函数...
string input = "1567438absdg345";
string result = "";
foreach(char c in input)
{
if(!Char.IsDigit(c))
{
break;
}
result += c;
}
回答by BrokenGlass
The Linq approach:
Linq 方法：
string input = "1567438absdg345";
string output = new string(input.TakeWhile(char.IsDigit).ToArray());
回答by f2lollpll
Another approach
另一种方法
private int GetFirstNum(string inp)
{
string final = "0"; //if there's nothing, it'll return 0
foreach (char c in inp) //loop the string
{
try
{
Convert.ToInt32(c.ToString()); //if it can convert
final += c.ToString(); //add to final string
}
catch (FormatException) //if NaN
{
break; //break out of loop
}
}
return Convert.ToInt32(final); //return the int
}
Test:
测试：
Response.Write(GetFirstNum("1567438absdg345") + "<br/>");
Response.Write(GetFirstNum("a1567438absdg345") + "<br/>");
Result:
结果：
1567438
0
1567438
0
回答by stema
Or the regex approach
或者正则表达式方法
String s = "1567438absdg345";
String result = Regex.Match(s, @"^\d+").ToString();
^matches the start of the string and \d+the following digits
^匹配字符串的开头和\d+后面的数字
回答by Zafer
An old-fashioned Regular expressionist way:
一种老式的正则表现主义方式：
public long ParseInt(string str)
{
long val = 0;
System.Text.RegularExpressions.Regex reg = new System.Text.RegularExpressions.Regex(@"^([\d]+).*$");
System.Text.RegularExpressions.Match match = reg.Match(str);
if (match != null) long.TryParse(match.Groups[1].Value, out val);
return val;
}
If it cannot parse, the method returns 0.
如果无法解析，则该方法返回 0。
回答by Thit Lwin Oo
Please try this
请试试这个
string val = "1567438absdg345";
System.Text.RegularExpressions.Regex reg = new System.Text.RegularExpressions.Regex("[1-9][0-9]*");
string valNum = reg.Match(val).Value;
回答by Sgedda
This way you get the first digit from the string.
这样你就可以从字符串中获得第一个数字。
string stringResult = "";
bool digitFound = false;
foreach (var res in stringToTest)
{
if (digitFound && !Char.IsDigit(res))
break;
if (Char.IsDigit(res))
{
stringResult += res;
digitFound = true;
}
}
int? firstDigitInString = digitFound ? Convert.ToInt32(stringResult) : (int?)null;
Another alternative that should do it:
应该这样做的另一种选择：
string[] numbers = Regex.Split(input, @"\D+");
I dont know why I got an empty string as a result in the numbers list above though?
我不知道为什么我在上面的数字列表中得到了一个空字符串？
Solved it like below, but seems a like the regex should be improved to do it immediately.
像下面那样解决它，但似乎应该改进正则表达式以立即执行。
string[] numbers = Regex.Split(firstResult, @"\D+").Where(x => x != "").ToArray();
