im trying to validate a string of text that must be in the following format,
The number "1" followed by a semicolon followed by between 1 and three numbers only - it would look something like this.
1:1 (correct)
1:34 (correct)
1:847 (correct)
1:2322 (incorrect)
There can be no letters or anything else except numbers.
Does anyone know how i can make this with REGEX? and in C#
The following pattern would do that for you:
^1:\d{1,3}$
Sample code:
string pattern = @"^1:\d{1,3}$";
Console.WriteLine(Regex.IsMatch("1:1", pattern)); // true
Console.WriteLine(Regex.IsMatch("1:34", pattern)); // true
Console.WriteLine(Regex.IsMatch("1:847", pattern)); // true
Console.WriteLine(Regex.IsMatch("1:2322", pattern)); // false
For more convenient access you should probably put the validation into a separate method:
private static bool IsValid(string input)
{
return Regex.IsMatch(input, @"^1:\d{1,3}$", RegexOptions.Compiled);
}
Explanation of the pattern:
^ - the start of the string
1 - the number '1'
: - a colon
\d - any decimal digit
{1,3} - at least one, not more than three times
$ - the end of the string
The ^ and $ characters makes the pattern match the full string, instead of finding valid strings embedded in a larger string. Without them the pattern would also match strings like "1:2322" and "the scale is 1:234, which is unusual".
