C# CSV writer

CsvWriter.cs

        public delegate void ValuesGetter(params Object[] values);
 
        private const char Comma = ',';
 
        private static readonly Regex _escapedChars = new Regex(@"[,""\r\n]");
 
        public static string ToCsv<T>(IEnumerable<T> enumerable, string headers, Action<T, ValuesGetter> valuesGetter)
        {
            var columnCount = headers.Count(c => c == Comma) + 1;
            var result = new StringBuilder();
            result.AppendLine(headers);
            
            ValuesGetter callback = values =>
            {
                if (values == null)
                {
                    throw new ArgumentNullException("values");
                }
                if (values.Length != columnCount)
                {
                    throw new ArgumentException("values");
                }

                isFirst = true;
                foreach (var value in values)
                {
                    if (isFirst)
                    {
                        isFirst = false;
                    }
                    {
                        result.Append(Comma);
                    }
                    if (value != null)
                    {
                        var text = string.Format(CultureInfo.InvariantCulture, "{0}", value);
                        if (_escapedChars.IsMatch(text))
                        {
                            text = "\"" + text.Replace("\"", "\"\"") + "\"";
                        }
                        result.Append(text);
                    }
                }
            };
            
            foreach (var item in enumerable)
            {
                valuesGetter(item, callback);
                result.AppendLine();
            }
            return result.ToString();
        }