Chris Sainty: Windows Phone 7–Asynchronous Programming

One thing that will strike you quickly if you go to make an app that communicates over the internet is that everything has to be done asynchronously. While this is bound to annoy at first, it is actually a good design decision by the development team because it forces the developer to keep the UI responsive. Sadly there is at least one instance where they broke their own rules but we will get to that another time, I will just say watch out for the Image control.

My preferred way of handling asynchronous programing is with a callback structure that uses delegates/lambdas. You could also use events but I find most of the memory leaks I create in applications are to do with events and not releasing subscriptions. Luckily for us we now have lambdas that make callbacks a piece of cake to write, you just need to watch out for a few gotchas. If you prefer delegates to lambdas, then the second point here will not apply to you, but the first will still catch the very novice.

 

Pod linkiem, asynchroniczne czytanie twitter’a poprzez json

za pomocą Chris Sainty: Windows Phone 7–Asynchronous Programming.

String Format for DateTime [C#]

This example shows how to format DateTime using String.Format method. All formatting can be done also using DateTime.ToString method.

Custom DateTime Formatting

There are following custom format specifiers y (year),M (month), d (day), h (hour 12),H (hour 24), m (minute), s (second),f (second fraction), F (second fraction, trailing zeroes are trimmed), t (P.M or A.M) and z(time zone).

Following examples demonstrate how are the format specifiers rewritten to the output.

[csharp]

// create date time 2008-03-09 16:05:07.123
DateTime dt = new DateTime(2008, 3, 9, 16, 5, 7, 123);

String.Format(“{0:y yy yyy yyyy}”, dt);  // “8 08 008 2008”   year
String.Format(“{0:M MM MMM MMMM}”, dt);  // “3 03 Mar March”  month
String.Format(“{0:d dd ddd dddd}”, dt);  // “9 09 Sun Sunday” day
String.Format(“{0:h hh H HH}”,     dt);  // “4 04 16 16”      hour 12/24
String.Format(“{0:m mm}”,          dt);  // “5 05”            minute
String.Format(“{0:s ss}”,          dt);  // “7 07”            second
String.Format(“{0:f ff fff ffff}”, dt);  // “1 12 123 1230”   sec.fraction
String.Format(“{0:F FF FFF FFFF}”, dt);  // “1 12 123 123”    without zeroes
String.Format(“{0:t tt}”,          dt);  // “P PM”            A.M. or P.M.
String.Format(“{0:z zz zzz}”,      dt);  // “-6 -06 -06:00”   time zone

[/csharp]

You can use also date separator / (slash) and time sepatator : (colon). These characters will be rewritten to characters defined in the current DateTimeForma­tInfo.DateSepa­rator and DateTimeForma­tInfo.TimeSepa­rator.

[csharp]

// date separator in german culture is “.” (so “/” changes to “.”)
String.Format(“{0:d/M/yyyy HH:mm:ss}”, dt); // “9/3/2008 16:05:07” – english (en-US)
String.Format(“{0:d/M/yyyy HH:mm:ss}”, dt); // “9.3.2008 16:05:07” – german (de-DE)

[/csharp]

 

Here are some examples of custom date and time formatting:

 

[csharp]

// month/day numbers without/with leading zeroes
String.Format(“{0:M/d/yyyy}”, dt);            // “3/9/2008”
String.Format(“{0:MM/dd/yyyy}”, dt);          // “03/09/2008”

// day/month names
String.Format(“{0:ddd, MMM d, yyyy}”, dt);    // “Sun, Mar 9, 2008”
String.Format(“{0:dddd, MMMM d, yyyy}”, dt);  // “Sunday, March 9, 2008”

// two/four digit year
String.Format(“{0:MM/dd/yy}”, dt);            // “03/09/08”
String.Format(“{0:MM/dd/yyyy}”, dt);          // “03/09/2008”

[/csharp]

 

Standard DateTime Formatting

 

In DateTimeForma­tInfo there are defined standard patterns for the current culture. For example property ShortTimePatternis string that contains value h:mm tt for en-US culture and value HH:mm for de-DE culture.

Following table shows patterns defined in DateTimeForma­tInfo and their values for en-US culture. First column contains format specifiers for the String.Format method.

 

Specifier DateTimeFormatInfo property Pattern value (for en-US culture)
t ShortTimePattern h:mm tt
d ShortDatePattern M/d/yyyy
T LongTimePattern h:mm:ss tt
D LongDatePattern dddd, MMMM dd, yyyy
f (combination of D and t) dddd, MMMM dd, yyyy h:mm tt
F FullDateTimePattern dddd, MMMM dd, yyyy h:mm:ss tt
g (combination of d and t) M/d/yyyy h:mm tt
G (combination of d and T) M/d/yyyy h:mm:ss tt
m, M MonthDayPattern MMMM dd
y, Y YearMonthPattern MMMM, yyyy
r, R RFC1123Pattern ddd, dd MMM yyyy HH':'mm':'ss 'GMT' (*)
s SortableDateTi­mePattern yyyy'-'MM'-'dd'T'HH':'mm':'ss (*)
u UniversalSorta­bleDateTimePat­tern yyyy'-'MM'-'dd HH':'mm':'ss'Z' (*)
(*) = culture independent

Following examples show usage of standard format specifiersin String.Format method and the resulting output.

 

[csharp]

// create date time 2008-03-09 16:05:07.123

DateTime dt = new DateTime(2008, 3, 9, 16, 5, 7, 123);

String.Format(“{0:y yy yyy yyyy}”, dt); // “8 08 008 2008” year

String.Format(“{0:M MM MMM MMMM}”, dt); // “3 03 Mar March” month

String.Format(“{0:d dd ddd dddd}”, dt); // “9 09 Sun Sunday” day

String.Format(“{0:h hh H HH}”, dt); // “4 04 16 16” hour 12/24

String.Format(“{0:m mm}”, dt); // “5 05” minute

String.Format(“{0:s ss}”, dt); // “7 07” second

String.Format(“{0:f ff fff ffff}”, dt); // “1 12 123 1230” sec.fraction

String.Format(“{0:F FF FFF FFFF}”, dt); // “1 12 123 123” %
[/csharp]
za pomocą String Format for DateTime C#.

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