How to get number from a string

Question

I would like to get number from a string eg: My123number gives 123 Similarly varchar(32) gives 32 etc

Thanks in Advance.

Answer 1

If there is going to be only one number buried in the string, and it is going to be an integer, then something like this:

 int n;
 string s = "My123Number";
 if (int.TryParse (new string (s.Where (a => Char.IsDigit (a)).ToArray ()), out n)) {
    Console.WriteLine ("The number is {0}", n);
 }

To explain: s.Where (a => Char.IsDigit (a)).ToArray () extracts only the digits from the original string into an array of char. Then, new string converts that to a string and finally int.TryParse converts that to an integer.

Answer 2

Loop through each char in the string and test it for being a number. remove all non-numbers and then you have a simple integer as a string. Then you can just use int.parse.

string numString;
foreach(char c in inputString)
    if (Char.IsDigit(c)) numString += c;
int realNum = int.Parse(numString);

Answer 3

var s = "varchar(32)";
int value = int.Parse(new string(s.Where(c => Char.IsDigit(c)).ToArray()));

Answer 4

You could do something like this, then it will work with more then one number as well

public IEnumerable<string> GetNumbers(string indata)
{
    MatchCollection matches = Regex.Matches(indata, @"\d+");
    foreach (Match match in matches)
    {
        yield return match.Value;
    }
}

Answer 5

you could go the regular expression way. which is normally faster than looping through the string

        public int GetNumber(string text)
        {
            var exp = new Regex("([0-9])+"); // find a sequence of digits could be \d+
            var matches = exp.Matches(text);

            if (matches.Count == 1) // if there's one number return that
            {
                int number =  int.Parse(matches[0].Value);
                return number
            }
            else if (matches.Count > 1)
                throw new InvalidOperationException("only one number allowed");
            else
                return 0;
        }

Answer 6

First write a specification of what you mean by a "number" (integer? long? decimal? double?) and by "get a number from a string". Including all the cases you want to be able to handle (leading/trailing signs? culture-invariant thousands/decimal separators, culture-sensitive thousands/decimal separators, very large values, strings that don't contain a valid number, ...).

Then write some unit tests for each case you need to be able to handle.

Then code the method (should be easy - basically extract the numeric bit from the string, and try to parse it. Some of the answers provided so far will work for integers provided the string doesn't contain a value larger than Int32.MaxValue).