从字符串C#中查找日期时间

您可以使用此RegEx，假设日期为DDMMYYYY格式，并且日期在1900-2099年的范围内，但可能会出现歧义。我还根据你在问题中的评论更新了这一点，即日期是从当月开始的。

public static void Main()
{ 
  // Leaves room for ambiguity if the random prefix or index suffix look 
  // like dates as well.
  var pattern = "((0[1-9]|[12][0-9]|3[01])(0[1-9]|1[012])((19|20)[0-9]{2}))";
  // Or, I see in your comment that the dates are from the current month. 
  // If so then this decreases the probability of a false match. You could
  // use the following pattern instead:
  var year =  DateTime.Today.Year;
  var month  = string.Format("{0:00}", DateTime.Today.Month);
  pattern = "((0[1-9]|[12][0-9]|3[01])(" + month + ")(" + year + "))";        
  var str = "D1011608201313";
  var matches = Regex.Matches(str, pattern);
  if (matches.Count == 0) return;
  var groups = matches[0].Groups;     
  int d, m, y;
  int.TryParse(groups[2].Value, out d);
  int.TryParse(groups[3].Value, out m);
  int.TryParse(groups[4].Value, out y);
  var date = new DateTime(y, m, d);
  Console.WriteLine(date);
}

RegEx的详细分类（来自RegexBuddy）：

((0[1-9]|[12][0-9]|3[01])(0[1-9]|1[012])((19|20)[0-9]{2}))
Match the regular expression below and capture its match into backreference number 1 «((0[1-9]|[12][0-9]|3[01])(0[1-9]|1[012])((19|20)[0-9]{2}))»
   Match the regular expression below and capture its match into backreference number 2 «(0[1-9]|[12][0-9]|3[01])»
      Match either the regular expression below (attempting the next alternative only if this one fails) «0[1-9]»
         Match the character “0” literally «0»
         Match a single character in the range between “1” and “9” «[1-9]»
      Or match regular expression number 2 below (attempting the next alternative only if this one fails) «[12][0-9]»
         Match a single character present in the list “12” «[12]»
         Match a single character in the range between “0” and “9” «[0-9]»
      Or match regular expression number 3 below (the entire group fails if this one fails to match) «3[01]»
         Match the character “3” literally «3»
         Match a single character present in the list “01” «[01]»
   Match the regular expression below and capture its match into backreference number 3 «(0[1-9]|1[012])»
      Match either the regular expression below (attempting the next alternative only if this one fails) «0[1-9]»
         Match the character “0” literally «0»
         Match a single character in the range between “1” and “9” «[1-9]»
      Or match regular expression number 2 below (the entire group fails if this one fails to match) «1[012]»
         Match the character “1” literally «1»
         Match a single character present in the list “012” «[012]»
   Match the regular expression below and capture its match into backreference number 4 «((19|20)[0-9]{2})»
      Match the regular expression below and capture its match into backreference number 5 «(19|20)»
         Match either the regular expression below (attempting the next alternative only if this one fails) «19»
            Match the characters “19” literally «19»
         Or match regular expression number 2 below (the entire group fails if this one fails to match) «20»
            Match the characters “20” literally «20»
      Match a single character in the range between “0” and “9” «[0-9]{2}»
         Exactly 2 times «{2}»

如果事先至少知道ID，您可以保证通过Regex 找到它

string result = Regex.Replace(source, @"^.*(0[1-9]|[12][0-9]|3[01])(0[1-9]|1[012])(20[0-9][0-9])" + ID + @"$", "$1-$2-$3");

您可以在RegEx捕获组中捕获字符串的各个部分，并单独引用它们。

var matches = Regex.Matches("D1011608201313",@".*([0-9]{2})([0-9]{2})([0-9]{4}).{2}$");
if (matches.Count!=0)
{
    var match = matches[0];
    var year = Convert.ToInt32(match.Groups[3].Value);
    var month = Convert.ToInt32(match.Groups[2].Value);
    var day = Convert.ToInt32(match.Groups[1].Value);
    var result = new DateTime (year,month,day); 
}