# DateTime parsing

# ParseExact

var dateString = "2015-11-24";

var date = DateTime.ParseExact(dateString, "yyyy-MM-dd", null);
Console.WriteLine(date);

11/24/2015 12:00:00 AM

Note that passing CultureInfo.CurrentCulture as the third parameter is identical to passing null. Or, you can pass a specific culture.

Format Strings

Input string can be in any format that matches the format string

var date = DateTime.ParseExact("24|201511", "dd|yyyyMM", null);
Console.WriteLine(date);

11/24/2015 12:00:00 AM

Any characters that are not format specifiers are treated as literals

var date = DateTime.ParseExact("2015|11|24", "yyyy|MM|dd", null);
Console.WriteLine(date);

11/24/2015 12:00:00 AM

Case matters for format specifiers

var date = DateTime.ParseExact("2015-01-24 11:11:30", "yyyy-mm-dd hh:MM:ss", null);
Console.WriteLine(date);

11/24/2015 11:01:30 AM

Note that the month and minute values were parsed into the wrong destinations.

Single-character format strings must be one of the standard formats

var date = DateTime.ParseExact("11/24/2015", "d", new CultureInfo("en-US"));
var date = DateTime.ParseExact("2015-11-24T10:15:45", "s", null);
var date = DateTime.ParseExact("2015-11-24 10:15:45Z", "u", null);

Exceptions

ArgumentNullException

var date = DateTime.ParseExact(null, "yyyy-MM-dd", null);
var date = DateTime.ParseExact("2015-11-24", null, null);

FormatException

var date = DateTime.ParseExact("", "yyyy-MM-dd", null);
var date = DateTime.ParseExact("2015-11-24", "", null);
var date = DateTime.ParseExact("2015-0C-24", "yyyy-MM-dd", null);
var date = DateTime.ParseExact("2015-11-24", "yyyy-QQ-dd", null);

// Single-character format strings must be one of the standard formats
var date = DateTime.ParseExact("2015-11-24", "q", null);

// Format strings must match the input exactly* (see next section)
var date = DateTime.ParseExact("2015-11-24", "d", null); // Expects 11/24/2015 or 24/11/2015 for most cultures

Handling multiple possible formats

var date = DateTime.ParseExact("2015-11-24T10:15:45", 
  new [] { "s", "t", "u", "yyyy-MM-dd" }, // Will succeed as long as input matches one of these
  CultureInfo.CurrentCulture, DateTimeStyles.None);

Handling culture differences

var dateString = "10/11/2015";
var date = DateTime.ParseExact(dateString, "d", new CultureInfo("en-US"));
Console.WriteLine("Day: {0}; Month: {1}", date.Day, date.Month);

Day: 11; Month: 10

date = DateTime.ParseExact(dateString, "d", new CultureInfo("en-GB"));
Console.WriteLine("Day: {0}; Month: {1}", date.Day, date.Month);

Day: 10; Month: 11

# TryParse

This method accepts a string as input, attempts to parse it into a DateTime, and returns a Boolean result indicating success or failure. If the call succeeds, the variable passed as the out parameter is populated with the parsed result.

If the parse fails, the variable passed as the out parameter is set to the default value, DateTime.MinValue.

TryParse(string, out DateTime)

DateTime parsedValue;

if (DateTime.TryParse("monkey", out parsedValue))
{
   Console.WriteLine("Apparently, 'monkey' is a date/time value. Who knew?");
}

This method attempts to parse the input string based on the system regional settings and known formats such as ISO 8601 and other common formats.

DateTime.TryParse("11/24/2015 14:28:42", out parsedValue); // true
DateTime.TryParse("2015-11-24 14:28:42", out parsedValue); // true
DateTime.TryParse("2015-11-24T14:28:42", out parsedValue); // true
DateTime.TryParse("Sat, 24 Nov 2015 14:28:42", out parsedValue); // true

Since this method does not accept culture info, it uses the system locale. This can lead to unexpected results.

// System set to en-US culture
bool result = DateTime.TryParse("24/11/2015", out parsedValue);
Console.WriteLine(result);

False

// System set to en-GB culture
bool result = DateTime.TryParse("11/24/2015", out parsedValue);
Console.WriteLine(result);

False

// System set to en-GB culture
bool result = DateTime.TryParse("10/11/2015", out parsedValue);
Console.WriteLine(result);

True

Note that if you are in the US, you might be surprised that the parsed result is November 10, not October 11.

TryParse(string, IFormatProvider, DateTimeStyles, out DateTime)

if (DateTime.TryParse(" monkey ", new CultureInfo("en-GB"),
    DateTimeStyles.AllowLeadingWhite | DateTimeStyles.AllowTrailingWhite, out parsedValue)
{
    Console.WriteLine("Apparently, ' monkey ' is a date/time value. Who knew?");
}

Unlike its sibling method, this overload allows a specific culture and style(s) to be specified. Passing null for the IFormatProvider parameter uses the system culture.

Exceptions

Note that it is possible for this method to throw an exception under certain conditions. These relate to the parameters introduced for this overload: IFormatProvider and DateTimeStyles.

NotSupportedException: IFormatProvider specifies a neutral culture
ArgumentException: DateTimeStyles is not a valid option, or contains incompatible flags such as AssumeLocal and AssumeUniversal.

# TryParseExact

This method behaves as a combination of TryParse and ParseExact: It allows custom format(s) to be specified, and returns a Boolean result indicating success or failure rather than throwing an exception if the parse fails.

TryParseExact(string, string, IFormatProvider, DateTimeStyles, out DateTime)

This overload attempts to parse the input string against a specific format. The input string must match that format in order to be parsed.

DateTime.TryParseExact("11242015", "MMddyyyy", null, DateTimeStyles.None, out parsedValue); // true

TryParseExact(string, string[], IFormatProvider, DateTimeStyles, out DateTime)

This overload attempts to parse the input string against an array of formats. The input string must match at least one format in order to be parsed.

DateTime.TryParseExact("11242015", new [] { "yyyy-MM-dd", "MMddyyyy" }, null, DateTimeStyles.None, out parsedValue); // true

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