How to formulate Regular expression for given example

I'm not very well versed with regular expressions. I've had to use them, maybe once every few years, and that was 开发者_开发百科mostly for course work. Anyways, the following question should be a fairly straight forward question/answer for anyone familiar with regular expressions.

I need to ensure that the text entered into a field follows the following format:

x y z

or

x,y,z

or

x y z / <same pattern can repeat for almost unlimited length>

or

x,y,z / <...> // Spaces after the comma are ok

where x, y and z can only be integers. The patterns cannot be intermixed, so you cannot have

x, y, z / x y z / ...

I've tried the following

([1-9] [1-9] [1-9])

to get the x y z part, but I don't know how to include the '/' nor the ','

Any suggestions?

Try to break your regular expression down into pieces. Then try to combine them.

For example, an integer like 1024 is a sequence of one ore more digits, i.e. [0-9]+. Etc.

Grammar:

digit     ::= [0-9]
space     ::= [ ]
slash     ::= [/]
comma     ::= [,]

integer   ::= digit+
separator ::= space | comma
group     ::= integer separator integer separator integer
group-sep ::= space slash space
groups    ::= group ( group-sep group )*

Regex:

([0-9]+[ ,][0-9]+[ ,][0-9]+)([ ][/][ ][0-9]+[ ,][0-9]+[ ,][0-9]+)*

I guess you can use

Regex r = new Regex("^([0-9]+([ ,]|, )[0-9]+(\\2)[0-9]+)( [/] ([0-9]+(\\2)[0-9]+(\\2)[0-9]+)+)*$");

var x1 = r.IsMatch("1,2 3");         // false
var x2 = r.IsMatch("1 3 2 / 1 2 3"); // true
var x3 = r.IsMatch("1,3,2");         // true
var x4 = r.IsMatch("1 3 2 / 1");     // false

Console.WriteLine((x1 == false) ? "Correct" : "Error");
Console.WriteLine((x2 == true) ? "Correct" : "Error");
Console.WriteLine((x3 == true) ? "Correct" : "Error");
Console.WriteLine((x4 == false) ? "Correct" : "Error");
Console.ReadLine();

Spliting in smaller pieces

[0-9]+  matches any number, even 0. If it can't start with 0
        you will have to change it
[ ,]    the separator allows a space or a comma
\\2     matches the same thing the second group matched (space or comma)

The second big parenthesis matches or not more iterations of this sequence if started by /.

If all separator needs to be exactly the same, replace them by \\2 (just don't replace the first, that is what it is going to match for the group 2).