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