Example: Changing Date Formats
The following code example uses the Regex.Replace method to replace dates that have the form mm/dd/yy with dates that have the form dd-mm-yy.
The following code shows how the MDYToDMY method can be called in an application.
using System; using System.Globalization; using System.Text.RegularExpressions; public class Class1 { public static void Main() { string dateString = DateTime.Today.ToString("d", DateTimeFormatInfo.InvariantInfo); string resultString = MDYToDMY(dateString); Console.WriteLine("Converted {0} to {1}.", dateString, resultString); } static string MDYToDMY(string input) { try { return Regex.Replace(input, "\\b(?<month>\\d{1,2})/(?<day>\\d{1,2})/(?<year>\\d{2,4})\\b", "${day}-${month}-${year}", RegexOptions.None, TimeSpan.FromMilliseconds(150)); } catch (RegexMatchTimeoutException) { return input; } } } // The example displays the following output to the console if run on 8/21/2007: // Converted 08/21/2007 to 21-08-2007.
The regular expression pattern \b(?<month>\d{1,2})/(?<day>\d{1,2})/(?<year>\d{2,4})\b is interpreted as shown in the following table.
|
Pattern |
Description |
|---|---|
|
\b |
Begin the match at a word boundary. |
|
(?<month>\d{1,2}) |
Match one or two decimal digits. This is the month captured group. |
|
/ |
Match the slash mark. |
|
(?<day>\d{1,2}) |
Match one or two decimal digits. This is the day captured group. |
|
/ |
Match the slash mark. |
|
(?<year>\d{2,4}) |
Match from two to four decimal digits. This is the year captured group. |
|
\b |
End the match at a word boundary. |
The pattern ${day}-${month}-${year} defines the replacement string as shown in the following table.
|
Pattern |
Description |
|---|---|
|
$(day) |
Add the string captured by the day capturing group. |
|
- |
Add a hyphen. |
|
$(month) |
Add the string captured by the month capturing group. |
|
- |
Add a hyphen. |
|
$(year) |
Add the string captured by the year capturing group. |
