Stumped on C# DateTime ToString() formatting problem

问题

I am getting some junk data returned from a ToString() call on a DateTime object in C# and I'm afraid I'm stumped after poking around with it for a while.

The function is supposed to format dates to be compliant with RFC 822 (as required by the RSS spec) and looks like:

public static string FormatPubDate(DateTime pubDate) 
{
    string _rfc822Format = "ddd, dd MMM yyyy HH:mm:ss";
    string _tmp = pubDate.ToUniversalTime().ToString(_rfc822Format);

    return pubDate.ToString(_tmp + " UT");
}

Which should be what I want, from what I can read of the DateTime ToString() docs.

However, for some dates it's generating junk:

 Console.WriteLine(FormatPubDate(new DateTime(2008, 12, 16, 13, 44, 33)));
 Console.WriteLine(FormatPubDate(new DateTime(2008, 12, 17, 13, 44, 33)));
 Console.WriteLine(FormatPubDate(new DateTime(2009, 3, 18, 4, 17, 20)));
 Console.WriteLine(FormatPubDate(new DateTime(2009, 4, 30, 10, 44, 33)));

Yields:

Tue, 16 Dec 2008 19:44:33 UT
We17, 17 Dec 2008 19:44:33 UT
We18, 18 3ar 2009 09:17:20 UT
T10u, 30 Apr 2009 15:44:33 UT

Any ideas why it's returning We18 instead of Wed and 3ar instead of Mar?

回答1:

You're problem is the last

return pubDate.ToString(_tmp + " UT");

You're doing a second ToString() on the DateTime with the formatted value, as the formatter...

Try changing it to

string _rfc822Format = "ddd, dd MMM yyyy HH:mm:ss";
string _tmp = pubDate.ToUniversalTime().ToString(_rfc822Format);

return _tmp + " UT";

回答2:

Can you use this instead?:

String.Format("{0:r}", dt);  // "Sun, 09 Mar 2008 16:05:07 GMT"   RFC1123

回答3:

You are currently calling ToString on the date, passing in your RFC format, then you are calling ToString on the date again, apssing in your already converted date + "UT" as the format, I'm suprised you get anything good coming out!

Try this:

public static string FormatPubDate(DateTime pubDate) 
{
    string _rfc822Format = "ddd, dd MMM yyyy HH:mm:ss";
    return pubDate.ToUniversalTime().ToString(_rfc822Format) + " UT";

}

来源：https://stackoverflow.com/questions/807690/stumped-on-c-sharp-datetime-tostring-formatting-problem

标签

datetime

rfc822