Question

I have never dealt with regular expressions before, and I am facing a problem here. The user has to input a text like Var1(0,enum1,enum2), and I have to check the syntax on the following manner:-

1- make sure Var1 name matches the list of variables I have.. Just a string comparison

2- make sure the parameters are input in sequence.

3- dropping any parameter is allowed. and also no parameter at all is allowed

then I have to take the parameters to fill up some object

will regex do the trick for me, or I have to go for writing a parser !?

Thanks!

Answer 1

I wouldn’t do this with a regular expression, but here’s one that does what you want (I am using general regexp syntax – nothing C# specific).

Assuming that the variables are var1, var2, var_3, and the the options for paramater 1 are par1_1, par1_2 and the options for parameter 2 are par2_1, par2_2, par2_3, etc then the regular expression is:

(var_1|var_2|var_3)\(((par1_1|par1_2|par1_3),)?((par2_1|par2_2,)?((par3_1|par3_2)?\)

Note that:

• (a|b|c) chooses one of a, b or c
• \( and \) match parentheses (plain “(” and “)” group)
• (…)? is optional
• There is a comma included after each optional parameter block, except the last.