下面是Linq版本:

string s = "123iuow45ss";
var getNumbers = (from t in s
                  where char.IsDigit(t)
                  select t).ToArray();
Console.WriteLine(new string(getNumbers));

这是我的算法

    //Fast, C Language friendly
    public static int GetNumber(string Text)
    {
        int val = 0;
        for(int i = 0; i < Text.Length; i++)
        {
            char c = Text[i];
            if (c >= '0' && c <= '9')
            {
                val *= 10;
                //(ASCII code reference)
                val += c - 48;
            }
        }
        return val;
    }

使用StringBuilder比在循环中连接字符串的性能稍好一些。如果处理的是大字符串，它的性能要高得多。

    public static string getOnlyNumbers(string input)
    {
        StringBuilder stringBuilder = new StringBuilder(input.Length);
        for (int i = 0; i < input.Length; i++)
            if (input[i] >= '0' && input[i] <= '9')
                stringBuilder.Append(input[i]);

        return stringBuilder.ToString();
    }

注意:上面的例子函数只适用于正数

对于那些想要十进制数字的字符串与Regex在两行:

decimal result = 0;
decimal.TryParse(Regex.Match(s, @"\d+").Value, out result);

同样的事情也适用于float, long等等…

  string verificationCode ="dmdsnjds5344gfgk65585";
            string code = "";
            Regex r1 = new Regex("\\d+");
          Match m1 = r1.Match(verificationCode);
           while (m1.Success)
            {
                code += m1.Value;
                m1 = m1.NextMatch();
            }

正则表达式。Split可以从字符串中提取数字。你会得到在字符串中找到的所有数字。

string input = "There are 4 numbers in this string: 40, 30, and 10.";
// Split on one or more non-digit characters.
string[] numbers = Regex.Split(input, @"\D+");
foreach (string value in numbers)
{
    if (!string.IsNullOrEmpty(value))
    {
    int i = int.Parse(value);
    Console.WriteLine("Number: {0}", i);
    }
}

输出:

数量:4 数量:40 数量:30 数量:10