How to identify a given string is hex color format

Question

I'm looking for a regular expression to validate hex colors in ASP.NET C# and
am also looking code for validation on server side.

For instance: #CCCCCC

Answer 1

Note: This is strictly for validation, i.e. accepting a valid hex color. For actual parsing you won't get the individual parts out of this.

^#(?:[0-9a-fA-F]{3}){1,2}$ 

For ARGB:

^#(?:[0-9a-fA-F]{3,4}){1,2}$ 

Dissection:

^              anchor for start of string #              the literal # (              start of group  ?:            indicate a non-capturing group that doesn't generate backreferences  [0-9a-fA-F]   hexadecimal digit  {3}           three times )              end of group {1,2}          repeat either once or twice $              anchor for end of string 

This will match an arbitrary hexadecimal color value that can be used in CSS, such as #91bf4a or #f13.