blocks|key|663202|text|您可以遍历字符串，并通过Char.isDigit测试当前字符是否为数字。***|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|663203|string+str+=+"1567438absdg345";
string+result+=+"";

for+(int+i+=+0;+i+<+str.Length;+i%2B%2B)+//+loop+over+the+complete+input
{
 + +if+(Char.IsDigit(str[i]))+//check+if+the+current+char+is+digit
 + + + +result+%2B=+str[i];
 + +else
 + + + +break;+//Stop+the+loop+after+the+first+character
}|code-block|syntax|javascript|663204|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/7f0ddtxh.aspx^0|C|C|C|C|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@$9|V|A|W|1|X]]|E|$]]|$1|F|3|G|5|H|7|Y|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]]]

You can loop through the string and test if the current character is numeric via <a href="http://msdn.microsoft.com/en-us/library/7f0ddtxh.aspx" rel="nofollow noreferrer"><code>Char.isDigit</code></a>.
       

<pre><code>string str = "1567438absdg345";
string result = "";

for (int i = 0; i &lt; 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
}
</code></pre>

blocks|key|663249|text|忘记正则表达式，在某个地方将其创建为helper函数...|type|unstyled|depth|inlineStyleRanges|entityRanges|data|663250|string+input+=+"1567438absdg345";
string+result+=+"";

foreach(char+c+in+input)
{
+++if(!Char.IsDigit(c))
+++{
++++++break;
+++}
+++result+%2B=+c;
}|code-block|syntax|javascript|663251|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|$]]

forget the regex, create this as a helper function somewhere...

<pre><code>string input = "1567438absdg345";
string result = "";

foreach(char c in input)
{
 if(!Char.IsDigit(c))
 {
 break;
 }
 result += c;
}
</code></pre>

blocks|key|449004|text|Linq方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|449005|string+input+=+"1567438absdg345";
string+output+=+new+string(input.TakeWhile(char.IsDigit).ToArray());|code-block|syntax|javascript|449006|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|$]]

The Linq approach:

<pre><code>string input = "1567438absdg345";
string output = new string(input.TakeWhile(char.IsDigit).ToArray());
</code></pre>

blocks|key|663364|text|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：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|663365|string+input+=+"1567438absdg345";

string+digits+=+new+String(input.TakeWhile(Char.IsDigit).ToArray());|code-block|syntax|javascript|663366|entityMap^0|5|9|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

You can use the <code>TakeWhile</code> extension methods to get characters from the string as long as they are digits:

<pre><code>string input = "1567438absdg345";

string digits = new String(input.TakeWhile(Char.IsDigit).ToArray());
</code></pre>

blocks|key|449092|text|另一种方法|type|unstyled|depth|inlineStyleRanges|entityRanges|data|449093|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+%2B=+c.ToString();+//add+to+final+string
++++++++}
++++++++catch+(FormatException)+//if+NaN
++++++++{
++++++++++++break;+//break+out+of+loop
++++++++}
++++}

++++return+Convert.ToInt32(final);+//return+the+int
}|code-block|syntax|javascript|449094|测试：|449095|++++Response.Write(GetFirstNum("1567438absdg345")+%2B+" ");
++++Response.Write(GetFirstNum("a1567438absdg345")+%2B+" ");|449096|结果：|449097|1567438|449098|0|449099|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

Another approach

<pre><code>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
}
</code></pre>

Test:

<pre><code> Response.Write(GetFirstNum("1567438absdg345") + "&lt;br/&gt;");
 Response.Write(GetFirstNum("a1567438absdg345") + "&lt;br/&gt;");
</code></pre>

Result:

1567438 
0

blocks|key|449140|text|或正则表达式方法|type|unstyled|depth|inlineStyleRanges|entityRanges|data|449141|String+s+=+"1567438absdg345";
String+result+=+Regex.Match(s,+@"%5E\d%2B").ToString();|code-block|syntax|javascript|449142|%5E匹配字符串的开头，并\d%2B以下数字|offset|length|style|CODE|449143|entityMap^0|0|0|0|1|B|3|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]|$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

Or the regex approach

<pre><code>String s = "1567438absdg345";
String result = Regex.Match(s, @"^\d+").ToString();
</code></pre>

<code>^</code> matches the start of the string and <code>\d+</code> the following digits

blocks|key|663458|text|老式的常规表现主义方式：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|663459|public+long+ParseInt(string+str)
{
++++long+val+=+0;
++++System.Text.RegularExpressions.Regex+reg+=+new+System.Text.RegularExpressions.Regex(@"%5E([\d]%2B).*$");
++++System.Text.RegularExpressions.Match+match+=+reg.Match(str);
++++if+(match+!=+null)+long.TryParse(match.Groups[1].Value,+out+val);
++++return+val;
}|code-block|syntax|javascript|663460|如果无法解析，则该方法返回0。|663461|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

An old-fashioned Regular expressionist way:

<pre><code>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;
}
</code></pre>

If it cannot parse, the method returns 0.

blocks|key|663472|text|请试试这个|type|unstyled|depth|inlineStyleRanges|entityRanges|data|663473|string+val+=+"1567438absdg345";

System.Text.RegularExpressions.Regex+reg+=+new+System.Text.RegularExpressions.Regex("[1-9][0-9]*");

string+valNum+=+reg.Match(val).Value;|code-block|syntax|javascript|663474|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|$]]

Please try this

<pre><code>string val = "1567438absdg345";

System.Text.RegularExpressions.Regex reg = new System.Text.RegularExpressions.Regex("[1-9][0-9]*");

string valNum = reg.Match(val).Value;
</code></pre>

blocks|key|663534|text|这样，您就可以从字符串中获得第一个数字。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|663535|string+stringResult+=+"";
bool+digitFound+=+false;
foreach+(var+res+in+stringToTest)
{
++++if+(digitFound+&&+!Char.IsDigit(res))
++++++++break;
++++if+(Char.IsDigit(res))
++++{
++++++++stringResult+%2B=+res;
++++++++digitFound+=+true;
++++}
}

int?+firstDigitInString+=+digitFound+?+Convert.ToInt32(stringResult)+:+(int?)null;|code-block|syntax|javascript|663536|另一个应该做到这一点的替代方案：|663537|string[]+numbers+=+Regex.Split(input,+@"\D%2B");|663538|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？|663539|像下面这样解决了它，但看起来像是正则表达式应该立即进行改进。|663540|string[]+numbers+=+Regex.Split(firstResult,+@"\D%2B").Where(x+=>+x+!=+"").ToArray();|663541|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

This way you get the first digit from the string.

<pre><code>string stringResult = "";
bool digitFound = false;
foreach (var res in stringToTest)
{
 if (digitFound &amp;&amp; !Char.IsDigit(res))
 break;
 if (Char.IsDigit(res))
 {
 stringResult += res;
 digitFound = true;
 }
}

int? firstDigitInString = digitFound ? Convert.ToInt32(stringResult) : (int?)null;
</code></pre>

Another alternative that should do it: 

<pre><code>string[] numbers = Regex.Split(input, @"\D+");
</code></pre>

I dont know why I got an empty string as a result in the numbers list above though? 

Solved it like below, but seems a like the regex should be improved to do it immediately.

<pre><code>string[] numbers = Regex.Split(firstResult, @"\D+").Where(x =&gt; x != "").ToArray();
</code></pre>

How to get the first numbers from a string?

Example: I have "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.

Get first numbers from String

如何从字符串中获取前几个数字？例如:我有"1567438absdg345“我只想得到没有"absdg345“的"1567438”，我希望它是动态的，得到字母表索引的第一个匹配项，并删除它之后的所有内容。

问从字符串中获取第一个数字
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