Regex for numbers only

yshuditelu_4660 0
Viewed 1178366

I haven't used regular expressions at all, so I'm having difficulty troubleshooting. I want the regex to match only when the contained string is all numbers; but with the two examples below it is matching a string that contains all numbers plus an equals sign like "1234=4321". I'm sure there's a way to change this behavior, but as I said, I've never really done much with regular expressions.

string compare = "1234=4321";
Regex regex = new Regex(@"[\d]");

if (regex.IsMatch(compare))
{ 
    //true
}

regex = new Regex("[0-9]");

if (regex.IsMatch(compare))
{ 
    //true
}

In case it matters, I'm using C# and .NET2.0.

regex c#
20 Answers

Use the beginning and end anchors.

Regex regex = new Regex(@"^\d$");

Use "^\d+$" if you need to match more than one digit.

Note that "\d" will match [0-9] and other digit characters like the Eastern Arabic numerals ٠١٢٣٤٥٦٧٨٩. Use "^[0-9]+$" to restrict matches to just the Arabic numerals 0 - 9.

If you need to include any numeric representations other than just digits (like decimal values for starters), then see @tchrist's comprehensive guide to parsing numbers with regular expressions.

Bill_the_Lizard_12880

Your regex will match anything that contains a number, you want to use anchors to match the whole string and then match one or more numbers:

regex = new Regex("^[0-9]+$");

The ^ will anchor the beginning of the string, the $ will anchor the end of the string, and the + will match one or more of what precedes it (a number in this case).

Robert_Gamble_252220

It is matching because it is finding "a match" not a match of the full string. You can fix this by changing your regexp to specifically look for the beginning and end of the string.

^\d+$
kasperjj_342400

^\d+$, which is "start of string", "1 or more digits", "end of string" in English.

user_21990 
 console.log(/^(0|[1-9][0-9]*)$/.test(3000)) // true
user_122124190

The following regex accepts only numbers (also floating point) in both English and Arabic (Persian) languages (just like Windows calculator):

^((([0\u0660\u06F0]|([1-9\u0661-\u0669\u06F1-\u06F9][0\u0660\u06F0]*?)+)(\.)[0-9\u0660-\u0669\u06F0-\u06F9]+)|(([0\u0660\u06F0]?|([1-9\u0661-\u0669\u06F1-\u06F9][0\u0660\u06F0]*?)+))|\b)$

The above regex accepts the following patterns:

11
1.2
0.3
۱۲
۱.۳
۰.۲
۲.۷

The above regex doesn't accept the following patterns:

3.
.3
0..3
.۱۲
user_57146020

To check string is uint, ulong or contains only digits one .(dot) and digits Sample inputs

Regex rx = new Regex(@"^([1-9]\d*(\.)\d*|0?(\.)\d*[1-9]\d*|[1-9]\d*)$");
string text = "12.0";
var result = rx.IsMatch(text);
Console.WriteLine(result);

Samples

123 => True
123.1 => True
0.123 => True
.123 => True
0.2 => True
3452.434.43=> False
2342f43.34 => False
svasad.324 => False
3215.afa => False
user_59512420
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