using System;
using System.Text.RegularExpressions;
public class Example
{
    public static void Main()
    {
        string pattern = @"\[(\s*[a-z]+\s+([a-z]+\s*)*)*,(\s*[a-z]+\s+([a-z]+\s*)*)*\]";
        string input = @" asa [   is his hair , grey or gray ] dsfs df";
        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