Find and extract a number from a string

Question

I have a requirement to find and extract a number contained within a string.

For example, from these strings:

string test = \"1 test\"
string test1 =         


        

Answer 1

Extension method to get all positive numbers contained in a string:

    public static List Numbers(this string str)
    {
        var nums = new List();
        var start = -1;
        for (int i = 0; i < str.Length; i++)
        {
            if (start < 0 && Char.IsDigit(str[i]))
            {
                start = i;
            }
            else if (start >= 0 && !Char.IsDigit(str[i]))
            {
                nums.Add(long.Parse(str.Substring(start, i - start)));
                start = -1;
            }
        }
        if (start >= 0)
            nums.Add(long.Parse(str.Substring(start, str.Length - start)));
        return nums;
    }

If you want negative numbers as well simply modify this code to handle the minus sign (-)

Given this input:

"I was born in 1989, 27 years ago from now (2016)"

The resulting numbers list will be:

[1989, 27, 2016]