F# - Parse dates | 易学教程

问题

Very basic question regarding parsing date in F#. I am very new to F# and .NET, so please bear with me.

My date has the format yyyyMMDD like 20100503.

How do I parse this into a DateTime type in F#.

I tried System.DateTime.Parse("20100503"); but get an error.

How do I pass a format string into the Parse method??

ANSWER is - Thanks everyone for the responses.

let d = System.DateTime.ParseExact("20100503", "yyyyMMdd", System.Globalization.CultureInfo.InvariantCulture);

回答1:

You should be able to use a custom format string. Try this:

System.DateTime.ParseExact("20100503", "yyyymmdd", null);;

See http://msdn.microsoft.com/en-us/library/8kb3ddd4.aspx for more details.

回答2:

DateTime.ParseExact("20100503", "yyyyMMdd", CultureInfo.CurrentCulture)

Use the ParseExact method and use lowercase d instead of upper.

回答3:

I answered a similar question this morning. I have not used F#, but if you have access to DateTime.ParseExact, my answer might help you.

You might also consider TryParseExact so that you can trap a failure based on the function returning false rather than having to put it inside of a try catch:

//Using code example from my previous answer...
string s = "100714 0700"; 
DateTime d;
if (!DateTime.TryParseExact(s, "yyMMdd hhmm", CultureInfo.InvariantCulture, out d))
{
  // Whoops!  Something is wrong with the date.
}


//In your case
string s = "20100503"; 
DateTime d;
if (!DateTime.TryParseExact(s, "yyyyMMdd", CultureInfo.InvariantCulture, out d))
{
  // Whoops!  Something is wrong with the date.
}

回答4:

The format is not one that is accepted.

http://msdn.microsoft.com/en-us/library/1k1skd40.aspx

You might need to manipulate the string before parsing.

you are on the right track though.

回答5:

You'll need to use the overload of DateTime.Parse which takes an IFormatProvider. The IFormatProvider you supply must understand that format.

You can do this by creating a DateTimeFormatInfo object with the correct format for the date string you are feeding to parse.

This is probably a lot of work for what you're doing. If you can reorganize the string a little first (most likely to a date string with seperators), you'll probably be better off.

来源：https://stackoverflow.com/questions/4158077/f-parse-dates

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datetime