C# : How to convert string to DateTime, where the string can have any of the standard datetime format

Question

I had posted a question on DateTime to String conversion, I got many satisfying answers for that .. so I thank StackOverflow very much ..
Here is one more problem of String

Answer 1

Here are all the possible formats ..

1. MM/dd/yyyy 08/22/2006
2. ffffdd, dd MMMM yyyy Tuesday, 22 August 2006
3. ffffdd, dd MMMM yyyy HH:mm Tuesday, 22 August 2006 06:30
4. ffffdd, dd MMMM yyyy hh:mm tt Tuesday, 22 August 2006 06:30 AM
5. ffffdd, dd MMMM yyyy H:mm Tuesday, 22 August 2006 6:30
6. ffffdd, dd MMMM yyyy h:mm tt Tuesday, 22 August 2006 6:30 AM
7. ffffdd, dd MMMM yyyy HH:mm:ss Tuesday, 22 August 2006 06:30:07
8. MM/dd/yyyy HH:mm 08/22/2006 06:30
9. MM/dd/yyyy hh:mm tt 08/22/2006 06:30 AM
10. MM/dd/yyyy H:mm 08/22/2006 6:30
11. MM/dd/yyyy HH:mm:ss 08/22/2006 06:30:07
12. MMMM dd August 22
13. yyyy'-'MM'-'dd'T'HH':'mm':'ss.fffffffK 2006-08-22T06:30:07.7199222-04:00
14. ffffd, dd MMM yyyy HH':'mm':'ss 'GMT' Tue, 22 Aug 2006 06:30:07 GMT
15. yyyy'-'MM'-'dd'T'HH':'mm':'ss 2006-08-22T06:30:07
16. HH:mm 06:30
17. hh:mm tt 06:30 AM
18. H:mm 6:30
19. h:mm tt 6:30 AM
20. HH:mm:ss 06:30:07
21. yyyy'-'MM'-'dd HH':'mm':'ss'Z' 2006-08-22 06:30:07Z
22. ffffdd, dd MMMM yyyy HH:mm:ss Tuesday, 22 August 2006 06:30:07
23. yyyy MMMM 2006 August

Answer 2

DateTime dt1 = DateTime.ParseExact("2007/01/01 04:23:12", "yyyy/MM/dd hh:mm:ss", System.Globalization.CultureInfo.CurrentCulture);

DateTime dt = Convert.ToDateTime("2007/01/01 04:23:12", System.Globalization.CultureInfo.CurrentCulture);

System.Globalization.CultureInfo.CurrentCulture format param

Answer 3

You can use the DateTime.ParseExact overload that takes a list of formats:

private static string[] formats = new string[]
    {
        "MM/dd/yyyy HH:mm:ss tt",
        "MM/dd/yyyy HH:mm:ss",
        "M/dd/yyyy H:mm:ss tt",
        "M/dd/yyyy H:mm:ss"        
    };

private static DateTime ParseDate(string input)
{
    return DateTime.ParseExact(input, formats, CultureInfo.InvariantCulture, DateTimeStyles.None);
}

This will throw a FormatException if the passed string does not match any of the given formats. Notice that the formats expecting AM/PM should appear before identical formats without AM/PM ("MM/dd/yyyy HH:mm:ss tt" comes before "MM/dd/yyyy HH:mm:ss").

Update
As Henk points out in the comments, the same functionality is available when using TryParseExact which removes exception situation. Also, paired with nullable types this can be made a bit cleaner:

private static DateTime? ParseDate(string input)
{
    DateTime result;
    if (DateTime.TryParseExact(input, formats, CultureInfo.InvariantCulture, DateTimeStyles.None, out result))
    {
        return result;
    }
    return null;
}

Now it will simply return a null reference if it fails to parse the input.

Answer 4

Take a look at the TryParseExact method. Here's an example with the first case:

DateTime date;
// I changed 02/31/2009 to 01/31/2009 because the first is not a valid date
if (DateTime.TryParseExact("01/31/2009 01:59:59", "MM/dd/yyyy HH:mm:ss", null, DateTimeStyles.None, out date))
{
    // string successfully parsed => do something with the date
}

You could then keep a list of different formats and try to parse the string with all of them until you succeed.