design wise why doesnt 0:00 return 2 digits?

Here is an example. I expected 1900/01/02 but got 1900/1/2 instead. If "1" was an int it would work. Why DOESNT this return 2 di开发者_StackOverflow社区gits? i understand its a string but isnt the point of :00 to specify the digits? Why is it being ignored?

var date = string.Format("{0:0000}/{1:00}/{2:00}", "1900", "1", "2");

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Because strings cannot be formatted like numbers; you can, however, specify a width of the target string (but they get padded with spaces, not 0).

var date = string.Format("{0,4}/{1,2}/{2,2}", "1900", "1", "2");

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Why are you trying to format a date from 3 strings, instead of using a DateTime variable?

Then you could format it easily:

DateTime dt = ...;
var dateString = dt.ToString("yyyy/MM/dd");
// yyyy = 4-digit year, MM = 2 digit month, dd = 2 digit day (with leading 0's)

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You need to convert to integer before it can be formatted as number:

var date = string.Format("{0:0000}/{1:00}/{2:00}", int.Parse("1900"), int.Parse("1"), int.Parse("2"));