Can anyone help out in converting this JAVA code into C#?

public static List<Operator> oprs = new List<Operator>();
private List<String> GetTokens(String s)
    {
        StringBuilder sb = new StringBuilder();
        sb.Append(Pattern.quote(oprs[0].symbol));

        for (int i = 1; i < oprs.Count; i++)
        {
            sb.Append("|");
            sb.Append(Pattern.quote(oprs.get(i).symbol));
        }
        sb.Append("|[a-zA-Z_]+[a-zA-Z0-9_]*\\([^()]*\\)|[0-9]+|[a-zA-Z_][a-zA-Z0-9_]*|\\Q(\\E|\\Q)\\E");

        List<String> tokens = new List<String>();
        Pattern p = Pattern.compile(sb.ToString());
        Matcher m = p.matcher(s);

        while (m.find()) tokens.add(m.group());
        return tokens;
    }

public static List<operator> oprs = new List<operator>();
private List<string> GetTokens(String s)
    {
Dictionary<string,> dictionary = new Dictionary<string,>()
            {
                {source, " " }
            };
            var matches = dictionary.SelectMany(a => Regex.Matches(s, a.Value)
            .Cast<match>()
            .Select(b=>
                    new
                    {
                        Index = b.Index,
                        Value = b.Value,
                        Token = a.Key
                    }))
            .OrderBy(a => a.Value).ToList();
            List<string> tokens = new List<string>();
            foreach(var items in matches)
            {
                tokens.Add(items.Value.ToString());
            }
return tokens;
}

private List GetTokens(String s)
{
    List tokens = new List();
    Regex rx = new Regex(@"|[a-zA-Z_]+[a-zA-Z0-9_]*\\([^()]*\\)|[0-9]+|[a-zA-Z_][a-zA-Z0-9_]*|\\Q(\\E|\\Q)\\E");

    MatchCollection matches = rx.Matches(s);
    if (matches.Count > 0)
    {
        Match match = matches[0];
        GroupCollection groupCollection = match.Groups;
    }

    foreach(var ma in matches)
    {
        tokens.Add(ma.ToString());
    }

    return tokens;
}