using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = @"^(?:(?:(?!^) (?:and|or) )?(?:\b[A-Z]|\B\([A-Z](?: (?:and|or) [A-Z])+\)\B)){2,}$";
string input = @"Valid:
A and B and C and D
(A or B) and C
(A or B or C) and D
(A or B or C or D) and E
A and (B or C) and D
A and (B or C) or (C and D)
A or (B and C)
(A and B) or (C and D)
Invalid:
A and B and C and
(A or B and C
(A or B or C) and D or
(A or B or C or D and E
A and or (B or C) and D
A and (B or (C and D)))
A (B and C)
(A and B) or C and D)
(A and B or C and D)
More Invalid:
A
AB or C
A and
or A and B
A and (A)
(A and B) or";
RegexOptions options = RegexOptions.Multiline;
foreach (Match m in Regex.Matches(input, pattern, options))
{
Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index);
}
}
}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for C#, please visit: https://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex(v=vs.110).aspx