date code and string reverse

[Dan Holmes]

I have a need to reverse a date to show as a "date code". For example
today, 090507 would be coded as 905070 (reversing the parts of the date.

This is what i have but there has to be a better way.

DateTime d = DateTime.Now;
string datecodemonth = d.ToString("MM" );
datecodemonth = datecodemonth[1] + datecodemonth[0];
string datecodeday = d.ToString("dd" );
datecodeday = datecodeday[1] + datecodeday[0];
string datecodeyear = d.ToString("yy" );
datecodeyear = datecodeyear[1] + datecodeyear[0];
string datecode = datecodemonth + datecodeday + datecodeyear;

Ideas? Is there anything in the format of the date that will do this?

dan

[Marc Gravell]

Seems a very odd thing to want to do, but why not ;-p
If this is high volume, then to avoid lots of intermediate strings,
try to work in a char[] buffer, something like:

static void Main(string[] args) {
char[] buffer =
DateTime.Today. ToString("MMddy y").ToCharArray ();
Swap(buffer, 0, 1); // perhaps unroll...
Swap(buffer, 2, 3);
Swap(buffer, 4, 5);
string s = new string(buffer);
Debug.WriteLine (s);
}
static void Swap(char[] data, int index1, int index2) {
char c = data[index1];
data[index1] = data[index2];
data[index2] = c;
}

[Mark Rae [MVP]]

"Dan Holmes" <da*******@bigf oot.comwrote in message
news:OU******** *****@TK2MSFTNG P06.phx.gbl...

Ideas? Is there anything in the format of the date that will do this?

Firstly, create a function to reverse a string:

string StringReverse(s tring pstrString)
{
char[] strArray = pstrString.ToCh arArray();
Array.Reverse(s trArray);
return new string(strArray );
}

Then do the following:

string strDateLiteral = "090507";
DateTime dtmDate = DateTime.ParseE xact(strDateLit eral, "MMddyy", null);
string strDateReversed =
StringReverse(d tmDate.ToString ("MM")) +
StringReverse(d tmDate.ToString ("dd")) +
StringReverse(d tmDate.ToString ("yy"));
--
Mark Rae
ASP.NET MVP
http://www.markrae.net

[UL-Tomten]

On Sep 5, 11:39 pm, Dan Holmes <danhol...@bigf oot.comwrote:

I have a need to reverse a date to show as a "date code". For example
today, 090507 would be coded as 905070 (reversing the parts of the date.

Both Mark's and Marc's examples use the default DateTime string format
provider, and then manipulates its results. A more .NET-ty solution
might be to implement a custom format provider, and use that to create
a string from a DateTime instead of the default provider. This would
avoid first going to 090507 and then to 905070, going directly to
905070 from a DateTime instance. See here for an example on how to
implement a custom format provider: http://www.codeproject.com/csharp/custstrformat.asp

[=?ISO-8859-1?Q?G=F6ran_Andersson?=]

Dan Holmes wrote:

I have a need to reverse a date to show as a "date code". For example
today, 090507 would be coded as 905070 (reversing the parts of the date.

This is what i have but there has to be a better way.

DateTime d = DateTime.Now;
string datecodemonth = d.ToString("MM" );
datecodemonth = datecodemonth[1] + datecodemonth[0];
string datecodeday = d.ToString("dd" );
datecodeday = datecodeday[1] + datecodeday[0];
string datecodeyear = d.ToString("yy" );
datecodeyear = datecodeyear[1] + datecodeyear[0];
string datecode = datecodemonth + datecodeday + datecodeyear;

Ideas? Is there anything in the format of the date that will do this?

You can do this with string operations or perhaps with a custom format
provider. I would however go for a numeric method, as the source is numeric.

Something like:

DateTime d = DateTime.Now;
int year = d.Year % 100;
int month = d.Month;
int day = d.Day;
string dateCode =
(month % 10).ToString() +
(month / 10).ToString() +
(day % 10).ToString() +
(day / 10).ToString() +
(year % 10).ToString() +
(year / 10).ToString();

--
Göran Andersson
_____
http://www.guffa.com

[Doug Semler]

"Göran Andersson" <gu***@guffa.co mwrote in message
news:OR******** ******@TK2MSFTN GP06.phx.gbl...

Dan Holmes wrote:

>I have a need to reverse a date to show as a "date code". For example
today, 090507 would be coded as 905070 (reversing the parts of the date.

This is what i have but there has to be a better way.

DateTime d = DateTime.Now;
string datecodemonth = d.ToString("MM" );
datecodemont h = datecodemonth[1] + datecodemonth[0];
string datecodeday = d.ToString("dd" );
datecodeday = datecodeday[1] + datecodeday[0];
string datecodeyear = d.ToString("yy" );
datecodeyear = datecodeyear[1] + datecodeyear[0];
string datecode = datecodemonth + datecodeday + datecodeyear;

Ideas? Is there anything in the format of the date that will do this?

You can do this with string operations or perhaps with a custom format
provider. I would however go for a numeric method, as the source is
numeric.

Something like:

DateTime d = DateTime.Now;
int year = d.Year % 100;
int month = d.Month;
int day = d.Day;
string dateCode =
(month % 10).ToString() +
(month / 10).ToString() +
(day % 10).ToString() +
(day / 10).ToString() +
(year % 10).ToString() +
(year / 10).ToString();

StringBuilder people...String Builder!!!

--
Doug Semler, MCPD
a.a. #705, BAAWA. EAC Guardian of the Horn of the IPU (pbuhh).
The answer is 42; DNRC o-
Gur Hfrarg unf orpbzr fb shyy bs penc gurfr qnlf, abbar rira
erpbtavmrf fvzcyr guvatf yvxr ebg13 nalzber. Fnq, vfa'g vg?

[=?ISO-8859-1?Q?G=F6ran_Andersson?=]

Doug Semler wrote:

"Göran Andersson" <gu***@guffa.co mwrote in message
news:OR******** ******@TK2MSFTN GP06.phx.gbl...

>Dan Holmes wrote:

>>I have a need to reverse a date to show as a "date code". For
example today, 090507 would be coded as 905070 (reversing the parts
of the date.

This is what i have but there has to be a better way.

DateTime d = DateTime.Now;
string datecodemonth = d.ToString("MM" );
datecodemon th = datecodemonth[1] + datecodemonth[0];
string datecodeday = d.ToString("dd" );
datecodeday = datecodeday[1] + datecodeday[0];
string datecodeyear = d.ToString("yy" );
datecodeyea r = datecodeyear[1] + datecodeyear[0];
string datecode = datecodemonth + datecodeday + datecodeyear;

Ideas? Is there anything in the format of the date that will do this?

You can do this with string operations or perhaps with a custom format
provider. I would however go for a numeric method, as the source is
numeric.

Something like:

DateTime d = DateTime.Now;
int year = d.Year % 100;
int month = d.Month;
int day = d.Day;
string dateCode =
(month % 10).ToString() +
(month / 10).ToString() +
(day % 10).ToString() +
(day / 10).ToString() +
(year % 10).ToString() +
(year / 10).ToString();

StringBuilder people...String Builder!!!

Why? A StringBuilder doesn't perform better, and there is no scalability
issues here.

If you want performance, this is four times faster:

DateTime d = DateTime.Now;
int year = d.Year % 100;
int month = d.Month;
int day = d.Day;
char[] c = new char[6];
c[0] = (char)((month % 10) + 48);
c[1] = (char)((month / 10) + 48);
c[2] = (char)((day % 10) + 48);
c[3] = (char)((day / 10) + 48);
c[4] = (char)((year % 10) + 48);
c[5] = (char)((year / 10) + 48);
return new string(c);

--
Göran Andersson
_____
http://www.guffa.com

[Jon Skeet [C# MVP]]

On Sep 7, 8:14 am, Göran Andersson <[e-mail] mwrote:

Doug Semler wrote:

"Göran Andersson" <[e-mail] mwrote in message
news:OR******** ******@TK2MSFTN GP06.phx.gbl...

Dan Holmes wrote:
I have a need to reverse a date to show as a "date code". For
example today, 090507 would be coded as 905070 (reversing the parts
of the date.

>This is what i have but there has to be a better way.

>DateTime d = DateTime.Now;
string datecodemonth = d.ToString("MM" );
datecodemont h = datecodemonth[1] + datecodemonth[0];
string datecodeday = d.ToString("dd" );
datecodeday = datecodeday[1] + datecodeday[0];
string datecodeyear = d.ToString("yy" );
datecodeyear = datecodeyear[1] + datecodeyear[0];
string datecode = datecodemonth + datecodeday + datecodeyear;

>Ideas? Is there anything in the format of the date that will do this?

You can do this with string operations or perhaps with a custom format
provider. I would however go for a numeric method, as the source is
numeric.

Something like:

DateTime d = DateTime.Now;
int year = d.Year % 100;
int month = d.Month;
int day = d.Day;
string dateCode =
(month % 10).ToString() +
(month / 10).ToString() +
(day % 10).ToString() +
(day / 10).ToString() +
(year % 10).ToString() +
(year / 10).ToString();

StringBuilder people...String Builder!!!

Why? A StringBuilder doesn't perform better, and there is no scalability
issues here.

If you want performance, this is four times faster:

DateTime d = DateTime.Now;
int year = d.Year % 100;
int month = d.Month;
int day = d.Day;
char[] c = new char[6];
c[0] = (char)((month % 10) + 48);
c[1] = (char)((month / 10) + 48);
c[2] = (char)((day % 10) + 48);
c[3] = (char)((day / 10) + 48);
c[4] = (char)((year % 10) + 48);
c[5] = (char)((year / 10) + 48);
return new string(c);

It only comes out 2.3 times faster for me, but there we go. This
version is between the two, and I prefer it for readability:

DateTime d = DateTime.Now;
string original = d.ToString("yyd dMM");
char[] c = original.ToChar Array();
Array.Reverse(c );
return new string(c);

Jon

[Marc Gravell]

[Smacks head] Why didn't I thnk of that!

Marc

[Jon Skeet [C# MVP]]

Doug Semler <do********@gma il.comwrote:

The compiler, in cases such as the one above, can optimize alot of the
instantiations out of the picture that you wouldn't see. This is because,
even though a string is treated as an Object, at runtime it is treated as a
Value class (struct).

No, it is certainly *not* treated as a struct. It's treated as a
reference type in every possible way.

Therefore, the compiler can actually perform compile
time value optimizations on strings. A simple example:

string MyFunc(int a, int b)
{
string sa = a.ToString();
string sb = b.ToString();
return sa + sb;
}

The compiler is smart enough to convert that into a concatination that is
back filled (basically what happens is an array of strings is created with
all of the "ToString" calls, on FINAL string is created, and the characters
of each string are then filled into the final string).

Um, any evidence of that?

I believe that 3 completely separate strings will be created in the
above code. There's no special optimisation going on as far as I'm
aware.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too