RegEx for pattern in c#

Question

I am still learning RegEx so I need some help on this one.

Rules are as below:

• Min/Max Length of string: 1-5
• String has to be a whole word
• String can contain: A-Z and/or a-z and/or 0-9 or combination of both only (e.g. _ - . * are not allowed)

Examples:

12345 – allowed
Os342 – allowed
2O3d3 – allowed
3sdfds dsfsdf – not allowed
Sdfdf.sdfdf –now allowed

Answer 1

^[a-zA-Z0-9]{1,5}$

• [a-zA-Z0-9] specifies the ranges allowed
• ^ specifies start of string
• $ specifies end of string
• {1,5} indicates minimum and maximum number of characters for the range

Answer 2

How about

^[A-Za-z0-9]{1,5}$

Answer 3

What about:

string input = "12345";
bool match = Regex.IsMatch(input, "^[a-z0-9]{1,5}$", RegexOptions.IgnoreCase);