DateTime.ParseExact throwing format exception for format “H”

Question

In the code below,keyValuePair[0] is a string representation of an hour 0-23,ie keyValuePair[0] == "2" to represent 2:00 AM. 13 for 1:00PM. I want to be able displaying this value in both 12 and 24 hour clocks.

an example:

keyValuePair[0] == 13 makes the value time equal "13:00" OR 1:00 PM" depending on the current Culture.

time = DateTime.ParseExact(keyValuePair[0], "H", CultureInfo.CurrentCulture).ToString("t");

This works only when keyValuePair[0] has a 2 digit value,and I switch the format "H" to "HH" .However, my input can possibly be 1 digit input.When the input is 1 digit long and I use the format "HH" I get an invalid format exception.

Perhaps there is a simpler way to do this? I guess I should just use "HH" and add a zero to keyValuePair[0]?

Answer 1

time = new DateTime(1, 1, 1, Convert.ToInt32(keyValuePair[0]), 0, 0).ToString("t");

Answer 2

"H" doesn't work because a single-character format string is assumed to be a standard date and time format string , but "H" is not one of the standard formats. To specify a custom format string with a single specifier , prefix the specifier with "%":

time = DateTime.ParseExact(keyValuePair[0], "%H", CultureInfo.CurrentCulture).ToString("t");

Note: Both DateTime.ParseExact and new DateTime(1, 1, 1, h, 0, 0) (Nimesh's answer) will validate that the specified hour is between 0 and 23. In contrast, DateTime.AddHours(h) and new TimeSpan(h, 0, 0) will accept values of h less than 0 or greater than 23.

Answer 3

只需使用PadLeft(2, '0')实现您想要的！

time = DateTime.ParseExact(keyValuePair[0].PadLeft(2, '0'), "HH", CultureInfo.CurrentCulture).ToString("t");

Answer 4

int input = int.Parse(keyValuePair[0]);
time = DateTime.Today.AddHours(input).ToString("t");