using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = @"\b(4[0-9]{3}[ -])([0-9]{4}[ -]){2}[0-9]\b|\b4[0-9][0-9]{11}\b|\b(4[0-9]{3}[ -])([0-9]{4}[ -]){2}(?:[0-9]{4})?$\b|\b4[0-9][0-9]{14}\b|\b(4[0-9]{3}[ -])([0-9]{4}[ -]){3}(?:[0-9]{3})?$\b|\b4[0-9][0-9]{17}\b";
string input = @"Visa:
Requirements: Visa numbers start with the number 4 and have either 13, 16, or 19 digits (new cards).
Pattern Parts:
Starts with number 4 and 13 length:
1) \b(4[0-9]{3}[ -])([0-9]{4}[ -]){2}[0-9]\b|\b4[0-9][0-9]{11}\b
Starts with number 4 and 16 length:
2) \b(4[0-9]{3}[ -])([0-9]{4}[ -]){2}(?:[0-9]{4})?$\b|\b4[0-9][0-9]{14}\b
Starts with number 4 and 19 length:
3) \b(4[0-9]{3}[ -])([0-9]{4}[ -]){3}(?:[0-9]{3})?$\b|\b4[0-9][0-9]{17}\b
Combining 1-3 to form one pattern:
\b(4[0-9]{3}[ -])([0-9]{4}[ -]){2}[0-9]\b|\b4[0-9][0-9]{11}\b|\b(4[0-9]{3}[ -])([0-9]{4}[ -]){2}(?:[0-9]{4})?$\b|\b4[0-9][0-9]{14}\b|\b(4[0-9]{3}[ -])([0-9]{4}[ -]){3}(?:[0-9]{3})?$\b|\b4[0-9][0-9]{17}\b
Test Cases:
Should fire:
13 length, no space, start with 4 4123123412341
13 length, dashes, start with 4 4123-1234-1234-1
13 length, spaces, start with 4 4123 1234 1234 1
16 length, no space, start with 4 4221123412341234
16 length, dashes, start with 4 4221-1234-1234-1234
16 length, spaces, start with 4 4221 1234 1234 1234
19 length, no space, start with 4 4241123412341234123
19 length, dashes, start with 4 4241-1234-1234-1234-123
19 length, spaces, start with 4 4241 1234 1234 1234-123
Should not fire:
16 length, no space, not start with 51-55 5623123412341234
16 length, dashes, not start with 51-55 5623-1234-1234-1234
16 length, spaces, not start with 51-55 5623 1234 1234 1234
16 length, no space, not start with 2221-2720 2220123412341234
16 length, dashes, not start with 2221-2720 2220-1234-1234-1234
16 length, spaces, not start with 2221-2720 2220 1234 1234 1234
Non 16 length, matches 51 pattern start 5123-1234-1234-123
Non 16 length, matches 2221 pattern start 2221-1234-1234-123
Malformed, matches 51 pattern start 51-2312-34-1234-1234
";
RegexOptions options = RegexOptions.Multiline;
foreach (Match m in Regex.Matches(input, pattern, options))
{
Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index);
}
}
}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for C#, please visit: https://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex(v=vs.110).aspx