String was not recognized as a valid DateTime on DateTime.ParseExact

Question

I know there is a lot of asked question here about DateTime but I saw them all already and seems not to find the right solution for my case.

Here is my code:

return DateTime.ParseExact(partialDate + dtfi.DateSeparator + _baseDate.ToString(), "dd/MM/yyyy", new CultureInfo("en-us");

This is throwing me an Exception.

Here is the value of the variables:

string partialDate = "1/22";
string dtfi.DateSeparator = "/";
int _baseDate = 2004;

Answer 1

您应该使用的格式"m/dd/yyyy"因为datestring成为1/22/2004

return DateTime.ParseExact(partialDate + dtfi.DateSeparator + _baseDate.ToString(), "m/dd/yyyy", new CultureInfo("en-us"));

Answer 2

Unfortunately , both answers are wrong.

So, we all agree your result string will be "1/22/2004" . Before looking which formats exactly matches your characters, let's look at your string is a standard date and time format for en-US culture or not.

DateTime.Parse("1/22/2004",
               CultureInfo.GetCultureInfo("en-US")) // 22 January 2004 00:00:00

BANG!

We have a DateTime perfectly. But what if our string wouldn't be a standard date and time format for en-US culture? Then we can specify our format with DateTime.TryParseExact method . Let's look at which formats we can use to parsing our string.

• 1 matches with "M" custom format specifier which is from 1 to 12 and single-digit month is formatted without a leading zero.
• / is a DateSeparator and we can use it the same in our format because en-US culture has / as a DateSeparator already. Remember, "/" custom format specifier has a special meaning of replace me with current culture or supplied culture date separator
• 22 matches with "dd" custom format string which is from 01 to 31 and single-digit days is formatted with a leading zero. Remember , you can also use d format specifier in such a case but using wider formats is recommended.
• 2004 matches with "yyyy" custom format specifier which represents the year with a four digits.

So, the right format will be M/dd/yyyy in result.

string s = "1/22/2004";
DateTime dt;
if(DateTime.TryParseExact(s, "M/dd/yyyy", CultureInfo.GetCultureInfo("en-US"),
                          DateTimeStyles.None, out dt))
{
    Console.WriteLine(dt); // 22 January 2004 00:00:00
}

Answer 3

You are referring to wrong format, so obviously it will throw exception. Below is what you are doing

string partialDate = "1/22";
string dtfi.DateSeparator = "/";
int _baseDate = 2004;

string ex = partialDate + dtfi.DateSeparator + _baseDate.ToString();

which gives you 1/22/2014 ie, MM/dd/yyyy

and in code you are referring to

return DateTime.ParseExact(partialDate + dtfi.DateSeparator + _baseDate.ToString(), "dd/MM/yyyy", new CultureInfo("en-us");

Try using correct Format, to get the right result.