去字符串中的内容

Question

字符串                      要取出的数
UISDA1.DAY2.E_QW,         2
UISDA1.DAY10.E_QW，      10
UISDA1.DAY100.E_QW，    100
UISDA1.UUPPI1.E_QW,     后面的1
UISDA1.ABCD4.E_QW          4

Answer 1

正则 
 @"(?is)(?<=DAY)[\d]+";

Answer 2

写了一个，楼主不懂正则就用土方法吧class Program
{
    static void Main(string[] args)
    {
        string[] content = 
            {
                "UISDA1.DAY2.E_QW,",
                "UISDA1.DAY10.E_QW，",
                "UISDA1.DAY100.E_QW，",
                "UISDA1.UUPPI1.E_QW,",
                "UUISDA1.ABCD4.E_QW"
            };        foreach (string str in content)
        {
            Console.WriteLine(ExtractNumber(str));
        }        Console.ReadLine();
    }    static string ExtractNumber(string txt)
    {
        string result = String.Empty;
        int start = txt.Length - 1;
        int end = start;
        while (start > 0)
        {
            if (txt[start] >= '0' && txt[start] <= '9')
            {
                end = start;
                while (start-- > 0)
                {
                    if ((txt[start] < '0' || txt[start] > '9'))
                        break;
                }
                result = txt.Substring(start + 1, end - start);
                break;
            }
            start--;
        }
        return result;
    }
}

Answer 3

(?<=\w+\.[A-Z]+)\d+
string str=@"UISDA1.DAY2.E_QW,         
UISDA1.DAY10.E_QW，    
UISDA1.DAY100.E_QW，    
UISDA1.UUPPI1.E_QW,     
UISDA1.ABCD4.E_QW";
foreach(Match m in Regex.Matches(str,@"(?<=\w+\.[A-Z]+)\d+"))
{
  Console.WriteLine(m.Value);
}

Answer 4

string str=@"UISDA1.DAY2.E_QW,         
UISDA1.DAY10.E_QW，    
UISDA1.DAY100.E_QW，    
UISDA1.UUPPI1.E_QW,     
UISDA1.ABCD4.E_QW";
foreach(Match m in Regex.Matches(str,@"(?<=\w+\.[A-Z]+)\d+"))
{
  Console.WriteLine(m.Value);
}

Answer 5

用string.LastIndexOf('.')也可以吧