Map string to string "pattern" - need fast solution

Hi  Smoerble;

The following code uses Regular Expression to reformat the text string to the correct format.

using System.Text.RegularExpressions;

        // Place these two statements at class level so that they are the most
        // high efficiency.
      private Regex re = new Regex(@"(?<yy>\d{4})(?<mm>\d\d)(?<dd>\d\d)" +
            @"(?<hh>\d\d)(?<min>\d\d)(?<ss>\d\d)(?<iii>\d{3})",
            RegexOptions.Compiled);
      private string replacePattern = "${dd}.${mm}.${yy} ${hh}:${min}:${ss}";

Then in your code insert the second line only, the string dateFormatted will have the date in the new format.

      string date = "20060320175422777"; // Test Data
      string dateFormatted = re.Replace( date, replacePattern);


I hope that this is of some help.

Fernando

Cool, will try it immediately.

Question about performance:
You say, if I add a HelperClass and then add this as a function this will be slower? If yes, will you recognize this performance issue if you use it 500 times on a page?

Example
string myDate = HelperDates.convertToFromatted("20060320175422777);

Finally, if you really want performance, you could use unsafe code...

  public static string Replace5(string date)
  {
    string newDate = new string(' ', FormattedLength);
    unsafe
    {
      fixed(char* pDate = newDate)
      {
        pDate[0] = date[6];
        pDate[1] = date[7];
        pDate[2] = '.';
        pDate[3] = date[4];
        pDate[4] = date[5];
        pDate[5] = '.';
        pDate[6] = date[0];
        pDate[7] = date[1];
        pDate[8] = date[2];
        pDate[9] = date[3];
        pDate[10] = ' ';
        pDate[11] = date[8];
        pDate[12] = date[9];
        pDate[13] = ':';
        pDate[14] = date[10];
        pDate[15] = date[11];
        pDate[16] = ':';
        pDate[17] = date[12];
        pDate[18] = date[13];
      }
    }
    return newDate;
  }

Output:

  Replace5: 265 ms

why not to have a dedicated Date\Time field in the table?
so the work at the coding.

@Kelmen:
I have to work with an existing DB and can't change the formats as I wish :(. Sorry not to mention it at first.

@Expert:
Wow. Thanks for this test, this is very very helpful. Can you give me a pointer to an explanation what "unsafe code" is?

@Fernando:
Thanks for the solution, works as designed :). Will spare points between you and Expert because of his tremendous test, hope you don't mind?

You could do a DateTime.ParseExact, which will be considerably faster than a regular expression.

Bob

 public static string Replace6(string date)
  {
    DateTime dateTime = DateTime.ParseExact(date, "yyyyMMddHHmmssfff", System.Globalization.CultureInfo.InvariantCulture);
    return dateTime.ToString("dd/MM/yyyy HH:mm:ss");
  }

  Replace6: 11906 ms

See, like that ^^

Bob

@Expert:
Can you give me a pointer to an explanation/tutorial what "unsafe code" is?

Sorry, I lost track of this one :(

http://www.codersource.net/csharp_unsafe_code.html
http://www.csharpfriends.com/Articles/getArticle.aspx?articleID=351
http://www.codeproject.com/csharp/unsafe.asp

Bob

Hi Bob;

I would like to get credit for answering this question as well seeming I gave the first working solution. The following statement was made by the author Smoerble.

@Fernando:
Thanks for the solution, works as designed :). Will spare points between you and Expert because of his tremendous test, hope you don't mind?

Thanks;

Fernando