Bad Compile constant value

Question

I get "Bad Compile constant value" on this statement.

Regex objCheckNumber = new Regex("^(\d){4}$");

I simply want to set this up to check another string to see if the value entered is 4 digits.

Answer 1

C# is trying to interpret \d as an escape sequence, and \d is not a valid escape sequence (but \n and \t are, for example). You can either double up the backslashes to escape it ("^(\\d){4}$"), or you can prefix the constant string with an at-sign: @"^(\d){4}$".

Answer 2

C# uses \ as an escape character. You need to double up the \ to \\.

Alternatively, place a @ character before the double-quote:

new Regex(@"^(\d){4}$")