blocks|key|1652396|text|我更喜欢这样的东西，它让你决定测试什么NumberStyle。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1652397|public+static+Boolean+IsNumeric(String+input,+NumberStyles+numberStyle)+{
++++Double+temp;
++++Boolean+result+=+Double.TryParse(input,+numberStyle,+CultureInfo.CurrentCulture,+out+temp);
++++return+result;
}|code-block|syntax|javascript|1652398|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/system.globalization.numberstyles.aspx^0|J|B|J|B|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]]]]

I prefer something like this, it lets you decide what <a href="http://msdn.microsoft.com/en-us/library/system.globalization.numberstyles.aspx" rel="noreferrer"><code>NumberStyle</code></a> to test for.

<pre><code>public static Boolean IsNumeric(String input, NumberStyles numberStyle) {
 Double temp;
 Boolean result = Double.TryParse(input, numberStyle, CultureInfo.CurrentCulture, out temp);
 return result;
}
</code></pre>

blocks|key|1438033|text|我知道已经有很多不同的方式回答了这个问题，有扩展和lambda示例，但将两者结合起来是最简单的解决方案。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1438034|public+static+bool+IsNumeric(this+String+s)
{
++++return+s.All(Char.IsDigit);
}|code-block|syntax|javascript|1438035|或者，如果您使用的是Visual+Studio+2015+(C#+6.0或更高版本)，则|1438036|public+static+bool+IsNumeric(this+String+s)+=>+s.All(Char.IsDigit);|1438037|很棒的C#6在一行上。当然，这是有限的，因为它只测试数字字符。|1438038|要使用，只需有一个字符串并在其上调用方法，例如：|1438039|bool+IsaNumber+=+"123456".IsNumeric();|1438040|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|$]]

I know this has been answered in many different ways, with extensions and lambda examples, but a combination of both for the simplest solution.

<pre><code>public static bool IsNumeric(this String s)
{
 return s.All(Char.IsDigit);
}
</code></pre>

or if you are using Visual Studio 2015 (C# 6.0 or greater) then

<pre><code>public static bool IsNumeric(this String s) =&gt; s.All(Char.IsDigit);
</code></pre>

Awesome C#6 on one line. Of course this is limited because it just tests for only numeric characters. 

To use, just have a string and call the method on it, such as:

<pre><code>bool IsaNumber = "123456".IsNumeric();
</code></pre>

blocks|key|1437717|text|是啊，IsNumeric是VB。人们通常使用TryParse()方法，尽管它有点笨拙。正如您所建议的，您可以随时编写自己的代码。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1437718|int+i;
if+(int.TryParse(string,+out+i))
{

}|code-block|syntax|javascript|1437719|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|$]]

Yeah, IsNumeric is VB. Usually people use the TryParse() method, though it is a bit clunky. As you suggested, you can always write your own. 

<pre><code>int i;
if (int.TryParse(string, out i))
{

}
</code></pre>

blocks|key|1652641|text|我喜欢扩展方法，但如果可能的话，我不喜欢抛出异常。我选择了一个扩展方法，在这里取两个答案中最好的一个。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1652642|++++///+<summary>
++++///+Extension+method+that+works+out+if+a+string+is+numeric+or+not
++++///+</summary>
++++///+<param+name="str">string+that+may+be+a+number</param>
++++///+<returns>true+if+numeric,+false+if+not</returns>
++++public+static+bool+IsNumeric(this+String+str)
++++{
++++++++double+myNum+=+0;
++++++++if+(Double.TryParse(str,+out+myNum))
++++++++{
++++++++++++return+true;
++++++++}
++++++++return+false;
++++}|code-block|syntax|javascript|1652643|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 like the extension method, but don't like throwing exceptions if possible.
I opted for an extension method taking the best of 2 answers here.

<pre><code> /// &lt;summary&gt;
 /// Extension method that works out if a string is numeric or not
 /// &lt;/summary&gt;
 /// &lt;param name="str"&gt;string that may be a number&lt;/param&gt;
 /// &lt;returns&gt;true if numeric, false if not&lt;/returns&gt;
 public static bool IsNumeric(this String str)
 {
 double myNum = 0;
 if (Double.TryParse(str, out myNum))
 {
 return true;
 }
 return false;
 }
</code></pre>

blocks|key|1652308|text|VB具有IsNumeric函数。您可以引用Microsoft.VisualBasic.dll并使用它。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1652309|entityMap^0|4|9|L|P|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

VB has the <code>IsNumeric</code> function. You could reference <code>Microsoft.VisualBasic.dll</code> and use it.

blocks|key|1652552|text|简单扩展：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1652553|public+static+bool+IsNumeric(this+String+str)
{
++++try
++++{
++++++++Double.Parse(str.ToString());
++++++++return+true;
++++}
++++catch+{
++++}
++++return+false;
}|code-block|syntax|javascript|1652554|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|$]]

Simple extension:

<pre><code>public static bool IsNumeric(this String str)
{
 try
 {
 Double.Parse(str.ToString());
 return true;
 }
 catch {
 }
 return false;
}
</code></pre>

blocks|key|1652403|text|public+static+bool+IsNumeric(string+anyString)
{
++++if+(anyString+==+null)
++++{
++++++++anyString+=+"";
++++}

++++if+(anyString.Length+>+0)
++++{
++++++++double+dummyOut+=+new+double();
++++++++System.Globalization.CultureInfo+cultureInfo+=+new+System.Globalization.CultureInfo("en-US",+true);
++++++++return+Double.TryParse(anyString,+System.Globalization.NumberStyles.Any,+cultureInfo.NumberFormat,+out+dummyOut);
++++}
++++else
++++{
++++++++return+false;
++++}
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1652404|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>public static bool IsNumeric(string anyString)
{
 if (anyString == null)
 {
 anyString = "";
 }

 if (anyString.Length &gt; 0)
 {
 double dummyOut = new double();
 System.Globalization.CultureInfo cultureInfo = new System.Globalization.CultureInfo("en-US", true);
 return Double.TryParse(anyString, System.Globalization.NumberStyles.Any, cultureInfo.NumberFormat, out dummyOut);
 }
 else
 {
 return false;
 }
}
</code></pre>

blocks|key|1437804|text|也许这是C#+3的一个特性，但你可以使用double.NaN。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1437805|entityMap^0|K|A|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

Maybe this is a C# 3 feature, but you could use <code>double.NaN</code>.

blocks|key|1652508|text|实际上，在所有.NET版本2.0和更高版本中都支持Double.NaN。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1652509|entityMap^0|P|A|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

Actually, <code>Double.NaN</code> is supported in all .NET versions 2.0 and greater.

blocks|key|1437935|text|我使用了Chris+Lively的代码片段(精选答案)，封装在一个布尔函数中，就像Gishu的建议一样，已经有一两年了。在继续进一步处理之前，我使用它来确保某些查询字符串只是数字。我开始得到一些错误的查询字符串，标记的答案没有处理，特别是在像"3645“这样的数字后面传递逗号时(返回true)。这是生成的mod：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1437936|+++static+public+bool+IsNumeric(string+s)
+++{
++++++double+myNum+=+0;
++++++if+(Double.TryParse(s,+out+myNum))
++++++{
+++++++++if+(s.Contains(","))+return+false;
+++++++++return+true;
++++++}
++++++else
++++++{
+++++++++return+false;
++++++}
+++}|code-block|syntax|javascript|1437937|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 was using Chris Lively's snippet (selected answer) encapsulated in a bool function like Gishu's suggestion for a year or two. I used it to make sure certain query strings were only numeric before proceeding with further processing. I started getting some errant querystrings that the marked answer was not handling, specifically, whenever a comma was passed after a number like "3645," (returned true). This is the resulting mod:

<pre><code> static public bool IsNumeric(string s)
 {
 double myNum = 0;
 if (Double.TryParse(s, out myNum))
 {
 if (s.Contains(",")) return false;
 return true;
 }
 else
 {
 return false;
 }
 }
</code></pre>

blocks|key|1438125|text|我有一个稍微不同的版本，它返回数字。我猜，在大多数情况下，在测试字符串之后，您会想要使用数字。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1438126|public+bool+IsNumeric(string+numericString,+out+Double+numericValue)
{
++++if+(Double.TryParse(numericString,+out+numericValue))
++++++++return+true;
++++else
++++++++return+false;
}|code-block|syntax|javascript|1438127|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 have a slightly different version which returns the number. I would guess that in most cases after testing the string you would want to use the number.

<pre><code>public bool IsNumeric(string numericString, out Double numericValue)
{
 if (Double.TryParse(numericString, out numericValue))
 return true;
 else
 return false;
}
</code></pre>

blocks|key|1652853|text|如果您不想只为isNumeric添加Microsoft.VisualBasic库的开销，下面是反向工程代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1652854|public+bool+IsNumeric(string+s)
{
++++if+(s+==+null)+return+false;

++++int+state+=+0;+//+state+0+=+before+number,+state+1+=+during+number,+state+2+=+after+number
++++bool+hasdigits+=+false;
++++bool+hasdollar+=+false;
++++bool+hasperiod+=+false;
++++bool+hasplusminus+=+false;
++++bool+hasparens+=+false;
++++bool+inparens+=+false;

++++for+(var+i+=+0;+i+<=+s.Length+-+1;+i%2B%2B)
++++{
++++++++switch+(s[i])
++++++++{
++++++++++++case+char+n+when+(n+>=+'0'+&&+n+<=+'9'):
++++++++++++++++++++if+(state+==+2)+return+false;+//+no+more+numbers+at+the+end+(i.e.+"1+2"+is+not+valid)

++++++++++++++++++++if+(state+==+0)+state+=+1;+//+begin+number+state
++++++++++++++++++++hasdigits+=+true;
++++++++++++++++++++break;

++++++++++++case+'-':
++++++++++++case+'%2B':
++++++++++++++++++++//+a+plus/minus+is+allowed+almost+anywhere,+but+only+one,+and+you+cannot+combine+it+with+parenthesis
++++++++++++++++++++if+(hasplusminus+%7C%7C+hasparens)+return+false;

++++++++++++++++++++if+(state+==+1)+state+=+2;+//+exit+number+state+(i.e.+"1-"+is+valid+but+1-1+is+not)
++++++++++++++++++++hasplusminus+=+true;
++++++++++++++++++++break;

++++++++++++case+'+':
++++++++++++case+'\t':
++++++++++++case+'\r':
++++++++++++case+'\n':
++++++++++++++++++++//+don't+allow+any+spaces+after+parenthesis/plus/minus,+unless+there's+a+$
++++++++++++++++++++if+(state+==+0+&&+(hasparens+%7C%7C+(hasplusminus+&&+!hasdollar)))+return+false;
++++++++++++++++++++if+(state+==+1)+state+=+2;+//+exit+number+state
++++++++++++++++++++break;

++++++++++++case+',':
++++++++++++++++++++//+do+not+allow+commas+unless+in+the+middle+of+the+number,+and+not+after+a+decimal
++++++++++++++++++++if+(state+!=+1+%7C%7C+hasperiod)+return+false;
++++++++++++++++++++break;

++++++++++++case+'.':
++++++++++++++++++++//+only+allow+one+period+in+the+number
++++++++++++++++++++if+(hasperiod+%7C%7C+state+==+2)+return+false;

++++++++++++++++++++if+(state+==+0)+state+=+1;+//+begin+number+state
++++++++++++++++++++hasperiod+=+true;
++++++++++++++++++++break;

++++++++++++case+'$':
++++++++++++++++++++//+dollar+symbol+allowed+anywhere,+but+only+one
++++++++++++++++++++if+(hasdollar)+return+false;

++++++++++++++++++++if+(state+==+1)+state+=+2;+//+exit+number+state+(i.e.+"1$"+is+valid+but+"1$1"+is+not)
++++++++++++++++++++hasdollar+=+true;
++++++++++++++++++++break;

++++++++++++case+'(':
++++++++++++++++++++//+only+allow+one+parens+at+the+beginning,+and+cannot+combine+with+plus/minus
++++++++++++++++++++if+(state+!=+0+%7C%7C+hasparens+%7C%7C+hasplusminus)+return+false;
++++++++++++++++++++hasparens+=+true;
++++++++++++++++++++inparens+=+true;
++++++++++++++++++++break;

++++++++++++case+')':
++++++++++++++++++++if+(state+==+1+&&+inparens)+state+=+2;+//+exit+number+state
++++++++++++++++++++if+(state+!=+2+%7C%7C+!inparens)+return+false;+//+invalid+end+parens
++++++++++++++++++++inparens+=+false;+//+end+parens+mode
++++++++++++++++++++break;

++++++++++++default:
++++++++++++++++++++//+oh+oh,+we+hit+a+bad+character
++++++++++++++++++++return+false;
++++++++}
++++}

++++//+must+have+at+leats+one+digit,+and+cannot+have+imbalanced+parenthesis
++++if+(!hasdigits+%7C%7C+inparens)+return+false;

++++//+if+we+got+all+the+way+to+here...
++++return+true;
}|code-block|syntax|javascript|1652855|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|$]]

If you don't want the overhead of adding the Microsoft.VisualBasic library just for isNumeric, here's the code reverse engineered:
<pre><code>public bool IsNumeric(string s)
{
 if (s == null) return false;

 int state = 0; // state 0 = before number, state 1 = during number, state 2 = after number
 bool hasdigits = false;
 bool hasdollar = false;
 bool hasperiod = false;
 bool hasplusminus = false;
 bool hasparens = false;
 bool inparens = false;

 for (var i = 0; i &lt;= s.Length - 1; i++)
 {
 switch (s[i])
 {
 case char n when (n &gt;= '0' &amp;&amp; n &lt;= '9'):
 if (state == 2) return false; // no more numbers at the end (i.e. &quot;1 2&quot; is not valid)

 if (state == 0) state = 1; // begin number state
 hasdigits = true;
 break;

 case '-':
 case '+':
 // a plus/minus is allowed almost anywhere, but only one, and you cannot combine it with parenthesis
 if (hasplusminus || hasparens) return false;

 if (state == 1) state = 2; // exit number state (i.e. &quot;1-&quot; is valid but 1-1 is not)
 hasplusminus = true;
 break;

 case ' ':
 case '\t':
 case '\r':
 case '\n':
 // don't allow any spaces after parenthesis/plus/minus, unless there's a $
 if (state == 0 &amp;&amp; (hasparens || (hasplusminus &amp;&amp; !hasdollar))) return false;
 if (state == 1) state = 2; // exit number state
 break;

 case ',':
 // do not allow commas unless in the middle of the number, and not after a decimal
 if (state != 1 || hasperiod) return false;
 break;

 case '.':
 // only allow one period in the number
 if (hasperiod || state == 2) return false;

 if (state == 0) state = 1; // begin number state
 hasperiod = true;
 break;

 case '$':
 // dollar symbol allowed anywhere, but only one
 if (hasdollar) return false;

 if (state == 1) state = 2; // exit number state (i.e. &quot;1$&quot; is valid but &quot;1$1&quot; is not)
 hasdollar = true;
 break;

 case '(':
 // only allow one parens at the beginning, and cannot combine with plus/minus
 if (state != 0 || hasparens || hasplusminus) return false;
 hasparens = true;
 inparens = true;
 break;

 case ')':
 if (state == 1 &amp;&amp; inparens) state = 2; // exit number state
 if (state != 2 || !inparens) return false; // invalid end parens
 inparens = false; // end parens mode
 break;

 default:
 // oh oh, we hit a bad character
 return false;
 }
 }

 // must have at leats one digit, and cannot have imbalanced parenthesis
 if (!hasdigits || inparens) return false;

 // if we got all the way to here...
 return true;
}
</code></pre>

What is the most efficient way of testing an input string whether it contains a numeric value (or conversely Not A Number)? I guess I can use <code>Double.Parse</code> or a regex (see below) but I was wondering if there is some built in way to do this, such as javascript's <code>NaN()</code> or <code>IsNumeric()</code> (was that VB, I can't remember?).

<pre><code>public static bool IsNumeric(this string value)
{
 return Regex.IsMatch(value, "^\\d+$");
}
</code></pre>

What is the C# equivalent of NaN or IsNumeric?

Visual Studio

测试输入字符串是否包含数值(反之不包含数字)的最有效方法是什么？我想我可以使用Double.Parse或正则表达式(见下文)，但我想知道是否有一些内置的方法可以做到这一点，比如javascript的NaN()或IsNumeric() (是VB吗，我不记得了？)。public static bool IsNumeric(this string value){    return Regex.IsMa

问什么是NaN或IsNumeric的C#等价物？
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回答 12

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