Get Date from String

If your dates are always in that format, you could try using a regex to grab the date string and then use DateTime.ParseExact to get the result you want:

public DateTime? GetFirstDateFromString(string input)
{
    DateTime d;

    // Exclude strings with no matching substring
    foreach (Match m in Regex.Matches(input, @"[0-9]{2}\.[0-9]{2}\.[0-9]{4}"))
    {
        // Exclude matching substrings which aren't valid DateTimes
        if (DateTime.TryParseExact(match.Value, "dd.MM.yyyy", null, 
            DateTimeStyles.None, out d))
        {
            return d;
        }
    }
    return null;
}

This will extract, parse and print all dates in the input text:

var regex = new Regex(@"\b\d{2}\.\d{2}.\d{4}\b");
foreach(Match m in regex.Matches(inputText))
{
    DateTime dt;
    if (DateTime.TryParseExact(m.Value, "dd.MM.yyyy", null, DateTimeStyles.None, out dt))
        Console.WriteLine(dt.ToString());
}

Now, if you just want the first date, you can do that:

static DateTime? GetFirstDateFromString(string inputText)
{
    var regex = new Regex(@"\b\d{2}\.\d{2}.\d{4}\b");
    foreach(Match m in regex.Matches(inputText))
    {
        DateTime dt;
        if (DateTime.TryParseExact(m.Value, "dd.MM.yyyy", null, DateTimeStyles.None, out dt))
            return dt;
    }
    return null;
}

Note that the method returns a nullable DateTime, so that it can return null when the string contains no date.

Try this:

using System;
using System.Text.RegularExpressions;

public class Example
{
   public static DateTime? GetFirstDateFromString(string input);
   {
      string pattern = @"\d{2}\.\d{2}\.\d{4}";
      Match m = Regex.Match(input, pattern);
      DateTime result;
      foreach(string value in match.Groups)  
          if (DateTime.TryParseExact(match.Groups[1], "dd.MM.yyyy", CultureInfo.CurrentCulture, DateTimeStyles.None, out result)
              return result;
      return null;
   }
}